Moonlighting as a plumber

It started out like any other one AM feeding. I rolled over groggily as my wife entered the room from getting water from the kitchen.

Only the words coming out of her mouth didn't sound right.

"Pardon?" I asked. Only in my half awake state it sounded like,  "Hrrrngh"?

"The kitchen sink is full of water and it's backing up. It smells bad. "

"Fngn shng." I replied.

I dragged my as out of bed to assess the situation. As my wife had noted, the kitchen sinks were indeed full of water and in danger of overflowing. Stuff was floating in the water and it didn't smell too pretty, although not as bad as sewage. (As evidenced by the fact that I failed to add last night's supper to the mess already in the sink.) I grabbed a pot and scooped up some water.

The water went into the bathroom sink, which proceeded to drain. Slowly. However, that indicated to me that I wasn't dealing with a back up at the street level. I dumped a few more pots of water into the toilet and went downstairs.

The lack of a foot of shitty water in the basement, or even any backed up drains, confirmed that I was dealing with a localized clog rather than a Poopocalypse. Indeed, it was only the kitchen drain that was plugged, and it's happened before. However, last time, the drain didn't back up on its own.

I was puzzled until I heard the water softener make noise. I glanced over and discovered that it was in the middle of a regeneration cycle. Since it shares the same drain as the kitchen, the clog was causing the drain water from the softener to back upstairs. However, I still wasn't awake enough to remember how to stop the softener from draining onto my kitchen floor, so I hurriedly shut off the house water supply.

Returning to the kitchen, I discovered that my lethargy had cost me. The kitchen sink had overflowed onto the floor. Out came the towels to soak up the thankfully small mess.

The last time this happened, I ran a snake down the drain until I punched through the wad of grease and coffee grounds that had blocked it. I set about to do the same this time, only I had a problem. The clean out port is at the bottom of the drain pipe. A pipe which is currently full of water. And which has a sink full of water on top of it. And since drain pipes aren't designed to hold standing water under pressure, a small puddle was already forming on the floor of the basement. I went back upstairs to bail out the kitchen sink.

Once the sink was empty, the water left in the pipe would fit into a five gallon pail. So I opened the clean out cap and managed to get most of the water into the pail.

Now for the fun part. I started with my fifteen foot sink snake. It reached the clog but couldn't open it; the snake's little head just wasn't up to busting up a mass of coffee flavored grease two inches across. Go figure.

So it was time to bring out his big brother. He's fifty or a hundred feet long, and the head is like three times the size. Problem is, using it is like wrestling a Python. A skinny, greasy, rusty, smelly Python. It doesn't have a convenient container like the little snake, so it's just awkward. However, since it's three in the morning and I don't have running water in my house, it would have to do.

I sent the snake down the pipe and bulled through what resistance I encountered. As I was working it into the drain, I was awake enough to start thinking of ways to store it other than simply leaving a big greasy coil of spring sort of wound up on the floor to get in the way. Then I saw the five gallon pail. By my estimate, the snake would coil up into the pail.

In theory. In practice, I got about three turns in before the thing unwound and jumped out of the pail. Version 2.0 involved sacrificing the lid of the pail. I cut a small hole in the center, just big enough to admit the snake, and attached it to the pail.

This time, the snake stayed in the pail while I pulled it back out of the drain. And when it was clear, I ran a couple buckets of water into the clean out. It didn't back up, so I declared my repair a temporary success. (I still had to clear the pipes, but that will take the use of chemicals I don't have. In the meantime, the drain should work until I can clean it properly.)

So I took off my plumber's hat for my janitor's cap, cleaned up the mess in the basement and the kitchen, and went back to bed for a couple hours.

50 Ohm Resistor Networks for Dummies

It's called a dummy load. No seriously, it is.

What's it for? Well, it gives the radio a place to send its power without radiating RF.

Why? It provides a nice consistent load for tuning the final amplifier stage on my radio before I transmit. It can also be used for testing the radio after a repair. Also, some radios transmit while receiving a program download from a computer (though they shouldn't.) This gives you a way to prevent such transmissions from interfering with others.

Why not just disconnect the antenna? Well, the radio forms one half of a resonant circuit. The antenna forms the other half. The most efficient circuit is one where both halves have the same impedance. For amateur radios, that ideal impedance is fifty ohms.

If you have an impedance mismatch, not all of the energy makes it from the transmitter to the antenna. The law of conservation of energy says that the energy that doesn't make it to the antenna has to go somewhere, and in this case, it gets reflected back to the radio. When it gets back to the radio, it gets turned into the heat in the final amplifier stage. Enough heat, and the radio dies.

As far as impedance mismatches go, a disconnected antenna is about as bad as you can get. That's why you should never run a radio without an antenna attached. When you fire up the transmitter, all the energy goes to the antenna connection, and finding nothing there, is reflected right back to the final amplifier. Since all the output from the radio gets instantly turned into heat, failure happens pretty quickly. The 50 ohm dummy load gives the power a place to go. It still gets turned into heat, but the heat is in the dummy load instead of the radio. And the dummy load is built to shed heat.

My dummy load is a network of 1k ohm resistors in parallel. The net resistance of this network is 50 ohms. The resistors are each able to dissipate 3 watts of power, so together the network can handle 60W.

However, my VHF radio is capable of putting out 75W, and my HF radio can pump out 100W. So, the resistor network sits in a 1L paint can filled with mineral oil. This will allow the resistors to take more heat before failing.

This build is based on a design by K4EAA. He also sells the pack of resistors needed to build it. (Not just any resistors will work, since some are built of a coil of wire. Such wire-wound resistors are OK for DC, but as soon as you pass RF through them, they act like inductors instead of resistors, and their impedance changes. These are metal-film resistors which have the same impedance at any frequency.)

Now, if only I could remember to switch back to the antenna after tuning the finals...

Hot Tubes in the Shack

These days, there's a ridiculous number of directions one can take in the hobby of amateur radio. But in the beginning, "amateur radio" meant someone banging out Morse Code on medium wave or shortwave.

Shortwave (HF) is the bread and butter of amateur radio. Before there were satellites, before transoceanic cables, people were using HF radios to communicate across the world. And they still do, since HF signals can get from their source to their destination without any equipment in between.

The main drawback is that the propagation of HF radio waves around the world is heavily dependent on atmospheric conditions. And this is where the challenge lies.

Since shortly after I got my license, I've been wanting to play with HF. I scored well enough that my license permits transmission on all the amateur bands. However, an HF rig isn't cheap. I'd need at least a few hundred dollars for a basic used rig, and with everything else that's going on right now, that just isn't in the cards. 

Enter the community. My situation came up in passing during a discussion over our weekly lunch meeting, and a fellow operator was more than happy to loan me one of his old rigs that had been languishing in his basement for some years. The following week, I helped him lug a Kenwood TS-530S and an AT-230 antenna tuner from his pickup to mine.

The tuner is especially important to my situation, and I'll get to it in a moment, but first I want to yak about the radio itself. Kenwood built these radios throughout the 1980s (I can't find a date stamp on my particular unit so I don't know when exactly it was manufactured.) They're what's called a hybrid rig, meaning that most of the electronics are solid state, but it uses vacuum tubes rather than transistors for the final RF amplifier (the part that puts the power out to the antenna).

Kenwood hybrid final compartment. Photo courtesy of k4eaa.com

Vacuum tubes have been largely replaced by transistors, even in ham radio, because they don't consume as much power, are smaller, and last longer (tubes have a lifespan, much like light bulbs, and radios using tubes are designed so that the tubes can be easily replaced.) However, tubes still find their uses in large RF power amplifiers, microwave ovens, audiophile amplifiers, etc.

The Kenwood hybrids are sought after among the ham community. (As an example, I recently found an eBay listing for a TS-530S selling for $300CAD - and it's broken.) While they're a simple rig, lacking many of the features in modern digital radios, they make up for it by being easy to use, robust, and easy to repair. The radio's much larger and heavier than a modern radio of equivalent functionality, but large discrete components are easier to remove and replace if something goes wrong.

It's actually a perfect starter rig for a ham just getting into HF.

For starters, it doesn't feel like a toy. I had an opportunity to use an Elecraft KX3 recently, and it wasn't much bigger than my handheld. The Kenwood lets you know that it means business. It's twenty kilos of radio sitting on my desk.

The other thing that makes it perfect for a starting ham is that it's all manual. The most modern thing about this rig is the digital frequency readout. There's no automatic antenna tuner, and you have to tune the final amplifier stage whenever you switch frequency bands. Having to learn about all this stuff teaches you things about how radios are built, and how signals propagate through your antenna and through the air. Things that you won't learn on a modern rig like an Elecraft K3. Don't get me wrong; I'd love to have a K3 in my shack, but it's like giving a calculator to a fourth-grader before teaching them long division. There's always the risk that they'll take the easy way out, and miss an important learning opportunity.

And learning is the reason that I got into ham radio in the first place.

Of course, this radio isn't without its drawbacks. For me, the biggest one is the lack of portability. Between being physically large and heavy, and being power-hungry, this rig isn't going camping with me. My goal of contacting hams on the other side of the world while sitting next to a campfire by a lake in the bush will have to wait until I can afford a smaller rig like the Yaesu 817D or an Elecraft KX3. However, for now, that's more than made up for by the fact that I'm on the air, with nothing more than a piece of clothes line strung between my house and my shed.

And that's where the tuner comes in. A radio and its antenna each form two halves of a resonant circuit, and to maximize power transfer from one half to the other, each half must have the same impedance. Since the impedance of an antenna is a function of the length of the antenna and the frequency of the signal, (this is an oversimplification, but it works for my purposes,) antennas have to be constructed with the proper length and spacing in order to work. Any random length of wire usually won't do, because it will be too long or too short, and this will cause RF energy to be reflected back to the radio. This reflected RF energy gets turned into heat in the radio's final stage, which eventually burns it out.

The tuner makes up for a badly tuned antenna by adding additional resistance or reactance to the antenna side of the resonant circuit so that it appears to be perfectly matched to the radio. This allows the radio to push maximum power to the antenna without risking damage. The drawback is that, since the antenna isn't truly resonant, some amount of transmitted power is soaked up by the tuner. The further out of tune the antenna is, the more power is wasted.

The silver lining of this cloud is that a tuner allows an operator to use any random length of wire as an antenna. It's not as efficient as a tuned antenna, but it gets my signal out into the air without risking letting the magic smoke out of my borrowed tubes. Twenty bucks worth of clothes line and a couple screw-in anchors has me talking to folks a few hundred kilometers away.

Cold Shower, anyone?

It all started on Easter weekend.

Friday morning, we got the trailer ready to go. I had waited until the last minute to fill the water system, because it was still freezing at night and I didn't want to risk any burst pipes. When the time came to fill the water heater, I opened the valves, only instead of being greeted by a healthy rushing of water, I heard only a hiss and trickle. Water issued from the hot water taps in a slow drizzle, rather than the rush I was expecting.

I'd run into this problem last year, and I thought I'd fixed it. Something was wrong with the bypass valves. Since I wouldn't need the valves until this fall, I figured I'd just take them out and deal with the problem when we got home. So I removed the valves and tossed them into the garage.

That evening, we're all set up at my sister-in-law's, and the kids are getting ready for bed. I turn on the pump so they can use the toilet. The pump starts running. And doesn't stop. My wife calls from outside, "there's water running out the side of the trailer!"

Crap. I quickly kill the pump and start investigating. The water heater has given me trouble in the past; judging by the soft floor around the heater I'm not the first victim, either. Unfortunately, since I'd removed the bypass valves, I had no way of shutting off the water supply to the tank. So, we couldn't use the water, and I had a wet floor. Again.

The next morning, after everyone got motivated, I took a closer look. Thankfully, my dad was more than willing to pop out and give me a hand. He brought with him an air compressor, and after blowing out the water lines, we started looking for the source of the leak. After ruling out the pipes, we pulled the tank itself. Hooking up the air compressor to the water tank made the pinholes in the bottom stand out really well. A quick trip to a local RV shop, and I had the fittings I needed to close the water system, without the tank. Now, we had cold and cold running water.

After returning home, I started exploring my options. While my wife would be perfectly happy losing the hot water tank and gaining some more storage, I liked the idea of having hot running water for things like washing dishes or brushing my teeth. So I looked into the cost of repairing or replacing the tank.

At this point I had no idea if the tank was repairable. Pinholes usually indicate corrosion; the material around the pinhole might be so thin that attempting to weld the hole shut may very well make the hole bigger. A skilled welder might be able to give me decent odds on the success of a repair, but before I had a chance to talk to one, I looked into the possibility of replacing the tank altogether.

Surprisingly, the design of RV water heaters hasn't changed much in 30 years. While features have been added (like automatic ignition and gas-electric units,) the dimensions have remained the same, and I was in fact able to find a brand-new unit that looked and operated exactly like my old one. However, it cost several hundred dollars, which was way out of my price range. A new heater was worth about half of what I'd paid for the trailer in the first place, which meant that if my current heater couldn't be fixed, I'd be going without hot running water.

And then I had a chance to talk to a welder at a local machine shop. Our conversation gave me confidence that a fix might be possible after all, so I left the heater with him for a couple of days. I got it back with a large patch welded over the entire bottom of the tank, which allayed any fears of corrosion-related failures in the future.

While the tank was out getting repaired, I examined the water damage. It was extensive, but I managed to repair it well enough. That's covered in another entry.

The tank had originally been wrapped in fiberglass wool insulation with a cardboard outer coating. Needless to say, this didn't survive the leak; the wool held the water like a sponge and the cardboard disintegrated. I'd pulled off the soaking, rotting insulation before repairing the tank, and before I installed it, I wrapped it in the foil-coated bubble wrap you can buy in a hardware store. Two layers made the tank too large to fit into the hole, but one layer doesn't seem to be adequate; the tank feels pretty warm to the touch, which means that a lot of heat is being lost through the tank walls. However, now that the tank is installed, I can reinstall the second layer and hold some more heat in the tank (instead of letting it out into the trailer, which is not the most desirable thing in the middle of the summer.)

I got the tank reinstalled, and then figured out what was wrong with the bypass valves. The handle of one of the valves was not properly lined up, which meant the valve never opened or closed properly. I realigned the handle, and the valves work properly.

So now I've got hot and cold running water again.

Baby Journey Part 2: Routine?

It's now 23 weeks.

A couple weeks ago we had an ultrasound in our local hospital, live-streamed to the medical team at BC Womens' Hospital in Vancouver. The ascites is unchanged. It's both good and bad news. It's not going away, but it's not getting any worse, either. I took that as good news; I need all of it I can get right now.

We just finished a set of appointments in Vancouver. However, this time we had a little bit of time to prepare for the trip; enough lead time that my wife was able to get in touch with a social worker in Vancouver who arranged for us to stay at the Ronald McDonald House on campus. Not only that, we qualified for financial support from the Variety Club. It honestly never occurred to me that this kind of help was available; I figured I'd have to make do on my own, and I was struggling to figure out how I was going to make ends meet while spending all this money to drive to and stay in Vancouver. I can't thank these guys enough for the help they've provided me. I've got enough to worry about without trying to figure out how I'm supposed to pay for all of it.

The first appointment was another two-hour ultrasound, scheduled for first thing Monday morning. The hospital bent their usual schedule a little for us so that we could reduce the number of days we spent out of town, and I could reduce the amount of work I would miss. The ultrasound was difficult, but it came from a completely unexpected source.

Puffy capacitors.

The baby was more or less fine; his condition is unchanged from the last scan two weeks prior. Our ultrasound tech was great. However, luck of the draw gave us the oldest ultrasound machine they had, and it had decided that it would slow down and freeze after ten or fifteen minutes of operation. That means our scans were regularly interrupted by a fatal error, and a five-minute reboot of the machine. It's about ten or twelve years old, which puts it in the time frame to be a victim of the capacitor plague. Not that I can say for certain, since I didn't open the machine up to take a look, but the manufacture time and the symptoms come together in a nice burst of serendipity.

After our ultrasound, we met with our social worker, who made sure we had a place to stay for our next appointment in four weeks' time. I gotta hand it to her. For us, the actual hospital appointment is but a small part of the entire experience; since we're out of town, there's so much more to worry about. Things like where we're going to sleep. She takes care of those things for us so that we don't have to worry about them, and instead we could worry about other things, like what we were going to eat at the cafeteria.

I find it amusing that the cafeteria has all sorts of healthy choices for beverages, but they carry Diet Coke instead of regular Coke.

Anyway, so with lunch out of the way, we met with a neonatologist. He presented us with the latest theory, that our baby has leaky lymph vessels. Normally, the lymph vessels collect lymph and return it to the circulatory system, but as it was explained to us, the lymph vessels in our baby are not properly formed, allowing lymph to leak out and collect in the abdominal cavity. Since the lymphatic system operates at a low pressure, the buildup eventually stabilizes when the pressure reaches equilibrium, which is why the baby's belly swelled up to a point and then stopped.

This condition is not uncommon, and normally corrects itself within weeks or months after birth. However, the fluid buildup must be drained shortly before birth, so that the baby is able to properly take his first breath. This is normally done with a needle through mom's abdomen, and since this procedure can't be done during active labour (because the abdominal wall is contracting and this would disrupt any procedure involving a needle through the abdominal wall,) we're looking at a caesarian section shortly before our due date. After birth, we're told the baby will have a drain installed, and then spend some time in the NICU while the lymph vessels close up. At that point, the drain is removed and we can go home.

Prior to that, though, the doctors are going to start doing nonstress tests to keep an eye on the baby and determine if any early intervention is needed. The first of these tests will happen on our next trip to Vancouver in early June; any earlier would be pointless as an intervention would carry little chance of a positive outcome anyway.

We returned home with a generally good feeling, and our next step all planned out. And since my next trip is nearly upon me, I should close this entry so that I can start the next one.

Baby Journey Part 1: Exposition

Crap, I'm exhausted.

Originally I wasn't going to blog this, but I changed my mind, so now I have to go back four months and try to remember everything. So bear with me.

It started back in late December. We were out of town visiting family for Christmas. At some point, my wife discovered that a certain Aunt was late to the party. A quick trip to the drug store confirmed it; we had a baby on the way.

At first, we kept it quiet. Some people found out right away; let's just say it's difficult to keep such a secret from your friends at the annual Drunken New Year's Eve party. But we didn't shout it from the rooftops. After the last miscarriage, we wanted to see how things progressed before we got too excited.

Fast forward to February. The medical community considers my wife to be an "advanced age" for pregnancy, so they want to keep a close eye on her for certain complications (for example, older women are more likely to bear a child with Down's Syndrome.) They scheduled us an ultrasound for 11 weeks.

I remembered the drill from last time; Mom goes in first and Dad waits outside, until the ultrasound tech gets all of the important measurements done. Then Dad can come in and pester him or her with inane questions and gawk at the image on the screen. When I was allowed into the room, I had a flashback to my last visit. That one had ended with awkward silences, terse phone calls, and a trip across the street to our doctor's office where we were ushered into a room and delivered the bad news. It sucks all around, but I feel for the ultrasound tech. I mean, think about it. You're sitting in a room with a happy expectant couple, and you've just discovered that their unborn child is dead. But you're not allowed to tell them that. But they're standing right there in front of you. So you send them to their doctor, and then clean up the room for the next patient. Like I said, it sucks.

The result of that experience is that I'm on edge every time I walk into the ultrasound room. Everything is on hold while I watch the screen intently, waiting to see motion. I only relax once I see a heartbeat.

And this time, my stomach-knotting uneasiness was unfounded. The tech showed us a little alien-looking thing on the screen, confirmed that all the things they were looking for were indeed there, and we went on our way. Pretty routine.

Then we found out from our doctor that a routine blood test had shown a 50/50 chance that our child would develop Down Syndrome. We were scheduled for an NT ultrasound to confirm this result.

So we go in for another ultrasound. We had a different tech this time, but he was also very friendly, chatting with us while probing around my wife's exposed belly with the transducer. He took the appropriate measurements, commenting that things looked to be in the normal range, and also pointed out the developing bone structure. All in all, our fetus looked normal and healthy. The tech commented that he would be surprised if this baby developed Down Syndrome.

Everything seemed to settle down at this point, for a while. We had another appointment with our doctor, where we discussed the uncertain results from the blood tests. The doctor mentioned that the only way to be sure was to have an amniocentesis done, but that there are risks associated with the procedure. The doctor told us he'd look into it and get back to us.

A few weeks later, my wife phoned me at work and told me that the doctor's office had just called her; we had an appointment the day after tomorrow and there was a package for me to pick up, including a map.

Map?

The murkiness was resolved when I got my hands on the package. It contained an appointment list and instructions on how to get to BC Women's Hospital in Vancouver.

We don't live anywhere near Vancouver. So I hurriedly booked three days off work (one for the appointments, and one for travel on either side,) and ran home to pack.

The package also contained pre-procedure instructions for an amniocentesis. Wait, what? I thought we weren't there yet. But I didn't have time to think about it. I was in a mild state of panic, arranging hotels and worrying about how I was going to pay for everything while we were living hand-to-mouth. All I have to say is, thank goodness the Bank likes me. I just assumed they gave us the procedure information just-in-case, and left it at that.

So, after eight hours of driving, we arrive in Surrey, catch some sleep in our hotel room, and then ride the train into Vancouver proper. Since we live in the great hinterland beyond Hope, there aren't a lot of shopping opportunities for maternity clothes, so we stopped at a mall on the way in and picked up a few things.

After lunch, we get to the hospital and get checked in. A nurse ushers us into a room and lays down a bunch of informed consent forms for the amnio. She explains that there is another test called a NIPT test which samples the mother's blood rather than the amniotic fluid. However, it is not as definitive as an amnio. Also, it's not covered by medical, and it will take longer to get the results. She explains how increased the risk of miscarriage is as a result of the amnio, compared to the average pregnancy, and gives us a few minutes to watch a video of the procedure while we make up our minds.

The risk of miscarriage weighs heavily on our minds; my wife has had four so far, so we naturally figure that our risk is higher than average. But in the end, we decide to go ahead with the amnio. The certainty of the results of the amnio is worth the slightly increased risk of problems.

We move into the procedure room. Two doctors, a nurse, and an ultrasound tech. My wife on the ultrasound bed, and me sitting on a chair at her feet. One doctor is going to insert a needle into my wife's uterus, through her abdominal wall, in order to extract some amniotic fluid. The ultrasound tech is going to provide an image of my wife's innards so the doctor can see what she's doing. The other doctor is supervising. The nurse stands at my wife's head and distracts her. Everything seems to be going well, but then the room gets quiet. The tech and the doctors start talking in jargon and shorthand. The nurse chats up my wife in an attempt to distract her. I look around confused; it's only later that I realize what's happening.

This is the beginning of an "oh shit" moment. Something's happened, and it's bad.

The procedure is completed successfully, and we're immediately ushered into a room across the hall. It's a little meeting room with a table, some chairs, and a couch. The two doctors follow us in, and explain to us that, while they can't say anything official since we're too early in the pregnancy for a detailed ultrasound, the noticed while they were guiding the needle that the fetus has a fluid buildup uncharacteristic of a normal healthy fetus. They introduce us to a condition known as hydrops fetalis, and tell us that there's a very good chance that our baby will be stillborn, if the pregnancy even goes to term.

They said a bunch of other stuff at this point, about Down Syndrome, and preparing for the worst, and thinking about terminating the pregnancy, but honestly I don't recall most of it. I recall the tears, and the anguish.

I do recall that at no time did anyone ever use the word "abortion", even though that's exactly what we were talking about. We danced around the subject many times, but no one could speak its name directly, like doing so would bring forth one of the Elder Gods to smite us or something. At the time I thought it seemed kind of silly.

The doctors concluded with, "let's wait to see the results of the amnio," and left us alone. After we'd exhausted our emotional batteries, we rode the train back to our hotel. We would have liked nothing more than to go straight back and sleep the rest of the day away; maybe we would wake up in the morning and realize that it was all just a nightmare. But we had one thing to do first.

We returned to the maternity store we'd visited that morning and returned everything we'd purchased.

The next day, we drove home in a haze. We spent the weekend in a sickening purgatory, unsure what to do next.

On Monday, we had another ultrasound at our local hospital. The tech had the notes from the Vancouver visit, but it would be a couple more days before we got the results of the amnio. However, while a close inspection of the fetus revealed a fluid accumulation in the abdomen known as ascites, nothing else appeared out of the ordinary. This made us feel a little better, but only a little.

The next day we had an appointment with our doctor. He looked over the notes in our file with confusion. "I don't know why then sent you home," he said, "normally they're better than this."

He went on to explain that with results like this, the hospital should have kept us there, at least until the results of the amnio came in. He likened their breaking us the bad news to telling someone that they have cancer, and then explaining that it's an easily-treatable cancer that isn't that serious. It doesn't matter; after the first sentence, your patient's brain has shut down trying to wrap itself around the idea that they're going to die from cancer. We were also only a day early for the detailed ultrasound, so it would have made sense for the hospital to simply keep us there for an extra day, rather than sending us home. He told us that he was going to call the hospital and let us know, that day, what the heck was going on.

Well, we didn't get a call from him that day. The next day, my wife called the office in the morning and left a message. Having not heard back, she called again in the afternoon; the office was overbooked and she still couldn't talk to the doctor. The next day, she was preparing to head down to the office for a sit-in when the doctor phoned. He had a bunch of news.

First, the results of the amnio had come back. The test was negative, which means that chromosomal anomalies such as Down Syndrome were ruled out. Second, there was an investigation started at the hospital in Vancouver to determine why they'd screwed up so badly. And finally, we had an ultrasound at our local hospital, that afternoon. Images from that ultrasound were going to be sent to Vancouver so that a doctor could determine if our baby had anemia. Anemia is a possible cause of the ascites, and is treatable, but such treatment had to be carried out right away if it was needed. As such, the diagnosis flowing from this ultrasound would determine if my wife was going to Vancouver that night, or the following week.

So we headed back to the hospital. This time, the ultrasound tech went through the standard images, and showed us all of the organs, in their proper place. Then she went on to measure the blood flow through various blood vessels in the fetus. Then we were done.

Or so we thought. Less than an hour after leaving the hospital, we got a phone call. The doctors in Vancouver wanted more measurements. So my wife refilled her bladder and we went back.

This time, the ultrasound machine was connected to a videoconferencing device, and our ultrasound was streamed live to a doctor in Vancouver. He got the measurements he needed, and told us that, based on what he saw, he wasn't concerned about anemia. So there was no reason to rush down to Vancouver. However, they did want to keep an eye on the ascites, so we might come down later the following week.

When we got home, we got a phone call from the hospital in Vancouver. Since our appointments were scheduled for Tuesday morning, and the office was now closed for Easter, we couldn't reschedule for later in the week.

Two short-notice trips to Vancouver in three weeks. Doesn't exactly fit in well with my OCD "plan everything first" way of doing things. On the bright side, since we were going to be seeing both of our families over Easter weekend, we could interrogate them for information to bring to the appointment with the genetic counsellor. We headed back home a day early from our Easter weekend trip, and headed down to Vancouver Monday morning.

Our first appointment on Tuesday was with the genetic counsellor. She took all the information we'd gleaned from our families over the past weekend, and put it together into a nice family tree. She used stencils and everything. She also asked my wife many questions about her previous pregnancies. How long they ran, how they ended, etc.

After that we got another ultrasound. This one took a couple hours; the tech took a boatload of images and measurements, then a doctor came in and took some more measurements, and then the doctor called the ultrasound tech back in to take still more measurements. It was a high resolution machine, so the images were much more detailed than we had back home. They catalogued all the organs, took many measurements of the baby, and checked the blood flow of not only several vessels in the fetus, but also the arteries between mom and the placenta. Everyone was chatty the entire time, which I took as a good sign.

Then we had lunch in the hospital cafeteria. While we were eating, a team of doctors was poring over my wife's file.

After lunch, we met with one of the doctors from that team. After going over all the data, they had concluded that, well, that they were puzzled. On the bright side, they could tell us with certainty that it wasn't Down Syndrome, or Edward's Syndrome, or any other chromosomal abnormality identified in the standard PCR panel run on the amniotic fluid. They also knew that it wasn't anemia, nor was it fifth disease. They gave us even odds that we'd have one of three outcomes:

1. The ascites would remain unchanged through the term of the pregnancy. One doctor mentioned that she'd delivered a baby in this condition, drained the abdominal fluid after birth, and it didn't come back
2. The fluid would go away on its own before birth.
3. The symptoms would develop into hydrops fetalis.

I took that to mean that we had two chances in three that the baby would be fine. But for now, we could only let the pregnancy progress and keep an eye on the situation. They scheduled us for another ultrasound at home in a couple weeks, and another in Vancouver in a month. They also took some more of my wife's blood to run another series of tests, looking for other infections that may have caused the fluid buildup.

So that's where we sit at 19 weeks. See why I'm exhausted?

Floored, Part 1

It would seem that the hot water tank in my trailer has been leaking for a number of years.

When we got the trailer last year, I noticed a soft spot in the floor near the tank, and while the tank was out at the shop being repaired, I decided to take a closer look. What I found almost made me wish that I hadn't. Ignorance is bliss, after all.

First off, a note about construction. This vintage of RV isn't made of prefabricated panels of exotic materials. It's just wood and tin. It's basically built like a house, only using lighter, cheaper stuff. On one hand, it means it's very vulnerable to rot from water damage. On the other hand, damage can be repaired more easily than more modern RVs, since materials are available at any building supply store.

The floor is built like a layer cake. On top is a layer of linoleum. Under that is a layer of 5/8" plywood. Then a layer of 1x2" lumber, spaced 24" apart, with fiberglass wool insulation in between. Then a layer of cardboard. Then styrofoam, and finally a sheet of aluminum.

What the plywood looked like, under the lino

As I peeled up the lino, I discovered that the water damage had dissolved the glue, and the lino came up easily. Beneath that, the plywood subfloor was still saturated with water. I cut away enough lino to find dry plywood, set a shallow depth on my circular saw, and started cutting.

Since I didn't know how thick the plywood was at this point, it took me two or three tries to get through the floor. I eventually found out that the plywood was 5/8" thick. I also found that the joists were 1x2" lumber, and that they were also pretty rotten. In fact, the ones that weren't rotted black from water damage were dry-rotted. However, it turns out that most of the structural integrity of the floor comes from the plywood itself; the lumber served only as spacers to keep the plywood off the layer of styrofoam.

Beneath the plywood, I found soaking wet insulation.

Under the plywood, between the joists, I found a layer of fiberglass wool insulation. This, of course, had managed to soak up water like a sponge, so I pulled up what I could reach and threw it out. Under the insulation I found a layer of cardboard which was wet with water. Tapping on the cardboard made a sound that made me think that there was a layer of styrofoam underneath, and some measurements indicated to me that there wasn't anything else between that and the layer of aluminum on the bottom of the trailer.

The cardboard beneath the insulation. Also wet.

The cardboard is continuous under the joists; at this point I didn't want to dig any further into the floor. I figured that the styrofoam would be impervious to water anyway, and I didn't want to cut holes in the exterior floor anyway. I dropped a fan in front of the mess to dry it out, and left it for a couple days.

From this I learned a couple important rules about repairing water damage:

1. There's always more rot than you think: You have to be prepared to remove more than you expected. The rot is easily hidden by the waterproof top layer.
2. It's still wet in there: most of the materials that make up a floor absorb water. The longer you've had a leak, the more water will have been soaked up by the materials. And they don't want to let it go. My trailer had been sitting for a couple weeks after I'd stopped the leak and mopped up the visible water, but the wood had soaked up so much, and the lino had trapped it there, that I was still pulling up soaking wet wads of fiberglass and pulpy handfuls of what used to be plywood when I started taking the floor apart.

I also learned an important lesson about water damage. Fix it as soon as possible. Tear it open and dry it out before it starts to rot, or your problems get worse by orders of magnitude.

It looks bad, and at this point I'm faced with two options. One will give me a serviceable trailer, if I'm willing to spend money and do some hard work. On the other hand, Beltane is fast approaching, and that's traditionally celebrated with a big fire. Stay tuned to see what I decided to do.

Getting ready for camping season

We picked up our trailer at a very reasonable price from very reasonable people toward the end of the last camping season. This means we got to use it just enough to really love it, and then it got put away for the winter. Fortunately, I have a nice big carport, which means the trailer was sheltered from the snow. I raised it on blocks to get the tires off the ground, flushed out the water system, brought the batteries in the house, and left it while the cold settled in.

But now, the crocuses are up, and the snow is gone from the roads, which means a new camping season is just around the corner. And that means it's time to get the RV trailer out of hibernation.

There are some tasks that are common to all RVs, like flushing the antifreeze out of the water system, reinstalling the batteries, and giving the running gear a good inspection. However, our trailer is pretty old, so there are some repair issues that need to be taken care of first.

Tires

The trailer tires were pretty bald when I parked it last fall, and they didn't grow any new tread over the winter, much to my disappointment. However, since the trailer was up on blocks, getting the tires replaced was pretty easy.

It's worth noting that, while passenger car tires will fit, there are tires made specifically for trailers, (they have "ST" in the sidewall marking,) and those are what should be used. Trailer tires have a thicker sidewall than car tires, so they can handle more weight and higher operating pressures. This adds up to a stiffer tire. On a car, this would be a bad thing as it would make for a harsh ride, but in a trailer, a soft ride is a problem as it makes the trailer more prone to swaying. ("Trailer sway" refers to that phenomenon where your trailer decides it wants to take you in a new direction. Like the ditch. Or oncoming traffic. At a hundred kilometers per hour.) Here is a video of what it looks like.

Bearings and Brakes

The gentleman that sold me the trailer is a heavy-duty mechanic, so I wasn't expecting any problems with the running gear. That said, he told me he hadn't touched the bearings in five years, so I figured they were due for an inspection. The brakes worked well for the few times I used the trailer last year, but since I would be exposing the brakes in the process of inspecting the bearings, it was a good time to check them out as well.

For each of the wheels, I removed the brake drum/hub assembly, cleaned the grease out of everything, and then inspected the bearings, races, and seals for damage. The bearings and races were in great shape, so I simply packed everything with grease and reassembled the hub. (Here are more detailed instructions.)

As for the brakes, all the magnets were in good shape, and the shoes all had enough lining on them to get through another season. Since this is my first time repacking bearings, I'm probably going to pull the hubs again next spring to see how well I did, and I can decide at that time if I want to replace the brakes or not.

(If you're interested in how electric trailer brakes work, watch this YouTube video.)

It's worth noting that bearings are pretty generic, so you can pick up a spare set, pack them with grease, and throw them in a ziplock bag. If you have a bearing failure on the side of the road, you can get underway with nothing more than some simple tools and about a half-hour of time, instead of having to abandon the trailer to seek help in the next town.

Electrical Upgrade

Being from the early eighties, the coach electrics on this trailer are pretty simple. All the gas-operated appliances have pilot lights, so the electricity is only needed for lights, the water pump, and the blower on the furnace. Electricity is supplied by a 12-volt battery mounted on the trailer tongue, and recharged by an onboard power supply when we're connected to shore power.

Since we bought the trailer, I added a couple power outlets for charging cellular phones and such. I also wanted to relocate the switch for the water pump to a more convenient location. We also do a lot of camping in places where there are no services, so I want to add another battery.

I installed a secondary fuse panel under the front bunk, so that I could put the water pump, light, and power outlets onto separate circuits (so that a short in the power outlet, for example, doesn't kill the water pump.) I also installed a relay near the pump so that I could move the switch further away using thinner wire.

Next, I installed a second battery under the dinette, next to the power distribution panel. It's connected in parallel with the other battery, secured to the floor, and vented to the outside. The venting is necessary since lead-acid batteries produce hydrogen gas when being charged.

Finally, I replaced the plug on the shore power line. The line uses 10 guage conductors, so it's good for 30 amps, but sometime in the past the 30-amp plug had been replaced with a 15-amp one. This was probably done for convenience; it's more common to find a 15-amp outlet than a 30-amp one. Adapters exist to connect this cable to a 30-amp outlet, but I would rather have to deal with the more common situation of plugging a 30-amp plug into a 15-amp outlet. I believe it is safer; if you use an adapter to connect a 30-amp cable to a 15-amp outlet, you know you'll never get more than 15 amps running through your shore power line (since the circuit breaker upstream from the outlet will limit current flow to 15 amps. However, if you use an adapter to connect a 15-amp plug to a 30-amp outlet, you can get 30 amps flowing through your connection. And the 15-amp plug is not designed to handle the extra current. This presents a fire hazard. I'm against fire hazards, so I spent $25 and bought the proper plug and an adapter.

Cheaper for a reason

So, my pressure washer packed it in this past weekend.

My son was rinsing off the truck, and all of a sudden the pitch of the pump changed.  He released the trigger, and the pump didn't shut off like it normally does.

I killed the power, and discovered that the washer was spraying water out of the pump housing.

After we finished rinsing the car with the regular nozzle, I tore apart the pressure washer in search of the problem.

The photo is the pump assembly. In the foreground is the fitting where the soap tank attaches. If you look closely, you can see a seam in the plastic.

That seam is the problem.

The seam has failed, so the pump no longer works. This is apparently a common problem with this type of pressure washer. There is no fix that I'm aware of. (A replacement pump costs as much as a whole new unit.)

In hindsight, I'm not surprised. This unit was cheap, less than $150 CAD. Even though it has a good brand name attached to it, it's at the bottom end of the pricing scale for pressure washers.

What did surprise me was the time to failure; I've owned this unit for about two years. I expected even a cheap unit to last longer than that, considering the care I was putting into it.

I learned three things from this experience:

1. Buy a pressure washer with an all metal pump. They cost more, but last longer.
2. It's cheaper for a reason.
3. Cheap crap is crap and no amount of maintenance or TLC will change that. I made sure to purge the water every fall, and I stored the unit in the basement so there was no chance of freezing. That didn't stop it from failing.

OK, I kinda already knew the second one. But I've learned that a pressure washer is really worth two or three times what I paid for mine, and rather than throw good money after bad, I have to decide if I really need one.

Garage door

My radio hobby has been put on hold.

With the arrival of March comes the melting of snow, which means that I, and not the weather, am the factor holding up my spring projects.

First and foremost of those projects is fixing the garage door.

Now, before I go any further, I'm going to point out that this article is for entertainment purposes only. Garage doors are dangerous if installed improperly, and you can easily injure or kill yourself or someone else, or cause a lot of property damage. So I don't recommend that you attempt to install or adjust an overhead door. Now, back to our regularly scheduled programming.

Back in January the spring announced its retirement with a loud bang. Normally this wouldn't be a big problem, except that the door assembly came from Wayne Dalton, which means it uses their proprietary counterbalance system, and because my door is too old, I would have to shell out several hundred dollars for a complete counterbalance kit.

Fortunately, my father had recently replaced his garage door. New doors tend to come as a kit, which means you get not only the door, but also the track, pulleys, cables, springs, and various sundry hardware to install it. This means that after all was said and done, my father was in possession of a complete counterbalance kit which, although old, was still very serviceable. Modifying my door to use the old spring system seemed a much more cost-effective option.

It turns out that not much has changed in garage door technology in the past several decades.

First, a brief primer for anyone who doesn't know how an overhead door works.

To start with, they're heavy. Mine is about 55 kg, or about 125 lbs., which is too heavy for me to lift, nevermind the garage door opener (which doesn't actually lift the door, but I'll get into that later.)

In order to make the door usable, it's attached to a counterbalance that reduces the weight of the door by exerting an upward force on the door to reduce the net force required to lift it.

The problem with an overhead door like mine is that their weight changes as they move up and down. This is because as each segment rounds the corner on the track, that segment no longer pulls the door downward. What this means is that simply attaching a pulley and weight to the door won't work; as soon as the door starts to go up, it will go out of balance and shoot up because the counterweight will be too heavy.

The answer to this is to use a spring. The force a spring exerts is proportional to its spring constant, which is determined by its manufacture,  and the amount that it is deflected (pushed away from its resting position). So, as the door is raised, the spring's deflection is reduced, and the system stays more or less in balance through the entire travel of the door.

Fitting the old spring system to the new door turned out to be easier than I expected. (I won't go into the gory details here.) I had to replace a couple brackets to make room for the larger pulleys. I had to modify the cables that connect the door to the spring mechanism. And finally, I had to cut the shaft upon which everything mounts, as the donor door was 6 feet wider than mine.

Once all the hardware was mounted, it was time to load the spring. Here was the moment of truth; the donor door was much larger and heavier than mine. It was also about a foot shorter. All this means that the springs might not work for my door.

Remember that the force exerted by a spring depends on its spring constant and the amount it is deflected? Well, I knew from doing the math that I needed to twist the spring at least eight full turns in order for it to work; any fewer and it would stop exerting a force on the door before it was fully open, which would cause the cables to come off the pulleys and jam the door.

The problem was that if the spring was too stiff, it would overpower the door before I got to eight turns, and the door would open by itself.

Now, the donor door had two springs, which shared the lifting force equally. My plan was to use one, which cut the lifting force in half, and hope that the door would balance.

As it turns out, my hope was not in vain. Ideally, the door should be balanced at all points in its travel (ie., not want to go up or down on its own when stopped at various points.) Mine isn't quite so good; it's balanced at the bottom, but gets a little lighter near the top. However, it's close enough that it's not dangerous, and there's enough tension on the cables, even at the very top, that the door works.

It's not so far out of balance that it causes the garage door opener any stress, which is the most important thing.

Oh, right, the garage door opener. I said I was going to explain what I meant when I said that it doesn't lift the door. Well, it doesn't, at least not directly. Mine has a horizontal track that pulls the door away from the wall and the door follows. This only works because the opener is pulling at the very top of the door, where it is ready to follow the horizontal track along the ceiling. This means that the opener is not very well able to cope with an unbalanced door, as it's not able to directly oppose the force of gravity that's holding the door closed. And that is why a balanced door is so important; if the door were too heavy, the opener won't be able to open it. At best, the opener will stall and shut down. At worst, the opener could burn out, or it could tear the top of the door apart (although I would bet that most openers are both too smart and too weak for this to happen. But hey, why take the chance?)

So that's one major springtime project out of the way. My next task is to get the RV trailer ready for camping season, since our first outing is in less than two weeks. Stay tuned.

Tuning my first antenna

So, I done gone and built my first antenna.

It's a simple directional antenna called a "yagi", designed to operate in the 2 meter amateur band (144-148MHz). The plans came from this QST magazine article. So far I'm out about $14 in parts and a couple hours' labor. (The plans are titled "7dB for seven bucks"; I chalk up the discrepancy to inflation and currency conversion).

The antenna works like this: there are three wire elements attached to a non conductive boom. The center element is the driven element; it is connected to the radio and is driven by it. The other two elements are called parasitic elements because they are not electrically connected to anything; they work by absorbing and reflecting the field produced by the driven element.

The longer element is called the reflector and the shorter one is the director. They work together to focus the field produced by the driven element, stretching it out along the axis of the boom and compressing it along the sides, in much the same way lenses and mirrors can be used to shape the light coming from a lamp.

But just like a musical instrument, building it is only half the job. Because an antenna is part of a resonant circuit, it must be tuned to match the radio to which it's attached. And the resonance changes with frequency, so the antenna must be tuned for the frequencies on which it will be used.

Now, I don't want to dive into a lot of electrical engineering here, partly because I don't completely understand it myself, so the short story is that a good measurement of how well your antenna is tuned is something called the standing wave ratio. Basically, if the antenna is out of tune, some of the power sent to it will be reflected back to the radio. The further out of tune, the more power is reflected. Too much reflected power will overheat and burn out the radio. The SWR is the measurement of how much power is reflected.

The resonant frequency is controlled by the length of the driven element. So tuning the antenna means changing the length of the driven element until the antenna resonates at the frequency you want. Since it's hard to make wires longer, I started with an antenna that was too long and trimmed the elements as necessary.

So how do you measure SWR? Why, with an SWR meter of course! Trouble is, I don't have one. However, a fellow operator was kind enough to lend me his antenna analyzer, which not only measures the SWR, but also the impedance, capacitance, inductance, and many other things. Since this is my first antenna, I'm not too worried about these things; I'm mainly concerned with building something that is an improvement over what I already have, without blowing up my radio, and an SWR below 2 will do that for me.

So I stood the antenna up on a step ladder in my back yard, hooked up the analyzer, and started tuning. Initially, the antenna resonated at about 130MHz, which is too low. I began trimming the driven element in 1/8" and 1/4" increments until I eventually got the antenna resonating at about 145MHz with an SWR of 1.6. This puts it nicely in the 2 meter amateur band.

How good is this? Well, before I packed everything away, I hooked the analyzer to the factory-built magnetic whip I have (A magnetic whip is an antenna which is magnetically stuck on the roof of your car). It resonates at 162MHz, has an SWR of 2.9 at 144MHz and an SWR of 2.4 at 148MHz. That doesn't sound very good, but if I were to give the manufacturer the benefit of the doubt, I would say that the poor readings are the result of the fact that a magnetic mounted antenna uses the surface to which it's stuck as a ground plane, which means it relies on a good electrical connection, something that is dependent on the type of paint used on the car (non-metallic paints will provide a poor electrical connection, which will hurt the antenna's efficiency.)

So while it's not the best antenna around, I'd say it's a good first try. Mainly I did it for the learning experience, and for that it was wildly successful, as it taught me an important lesson about antenna-feedline interaction:

The feedline gets in the way, electrically speaking. I originally had the coax feedline hanging down the mast in the center, which puts it inline and near to the driven element. On the advice of a fellow operator, I routed the feedline along the boom to the rear. This meant the coax was now running perpendicular to the antenna elements instead of parallel to them, which had a significant impact on resonance, impedance, and SWR. Future designs will take this into account from the beginning.

Portable shack: Powering up

I needed a power supply for my Yaesu mobile. Often times, such as when programming,  I find myself wanting to power up the radio in the house. However, since the radio is designed to run in a car, it wants 12 volts DC. 

To maintain flexibility, I've wired the Yaesu with an Anderson connector, and built a cable to plug into a car cigarette lighter socket. This allows me to drop it into a car easily. For use inside the house, I have a power supply from an electric cooler, which plugs into the wall and supplies 12 volts to just such a socket. 

However, this power supply isn't up to the task of supplying the current necessary to drive the radio at full power; I can turn the radio on and program it, but if I try to transmit at anything above minimum power, the little power supply shuts down. 

Now, lucky for me, a computer power supply can also supply 12 volts. And depending on the unit, it can supply quite a lot of power. But you can't simply plug a radio into a computer power supply.

For starters, the plugs don't match. The power supply has many special connectors for the computer motherboard, drives, etc., while the radio uses a different connector. (in my case, an Anderson SBS connector that I'd scrounged.)

Secondly, while this power supply is able to deliver 10 amps on the 12V rail, none of the components connected to it need that much current all by themselves. Thus, the power supply has several 12V wires going to different places. The radio, on the other hand, wants that 10A all to itself, which makes these little wires less than optimal, (and probably a fire hazard.)

And finally, there are a lot more wires than I need. The power supply can not only deliver 12V, but can also deliver 5V and 3.3V, for other uses inside a computer. The radio doesn't need any of these other voltages.

This is a power supply I rescued from a computer destined for the recyclers. The first thing I needed to do was remove the rat's nest of wires hanging out the back. To keep things clean, I wanted to desolder everything from the board and replace it all with a single Anderson SBS connector. Fortunately, the holes in the board are large enough to accept the 10 guage wire that's on my connectors; the challenge was finding a soldering gun large enough. The wires themselves will carry heat away from the joint, so you need a gun large enough to put heat into the joint faster than the wires can carry it away. A torch would do the trick, but it would also burn the board.

Once I had removed all the wires, I soldered the Anderson connector onto the board. There's just enough wire to carry the connector outside the case, where I could bolt it to the chassis (as a strain relief.)

The next task was to provide a way to turn the power supply on. This is an ATX power supply, which means it's normally controlled by the computer. The computer is able to turn itself on and off, but it also means that there isn't a switch on the power supply; there's no way to turn it on unless it's connected to a computer.

Well, a little research on the internet showed me that if you tie one of the wires to ground, the power supply will come on, and breaking that connection will turn the power supply off. So I drilled a hole in the back of the case, installed a toggle switch, and connected it between this lead and ground.

This power supply is able to drive my Yaesu at full power (75 watts) without any problems. It supplies just a shade under 12 volts, which is less than the car, but the radio doesn't seem to mind. 

Portable Shack: The Next Generation

My first design for a portable radio shack has died on the drawing board.

After a bit of thinking, I decided that a single box to contain all my radio gear would simply be too big. Starting with a 30kg battery and adding a few radios would have resulted in a box that was just too much to haul around in a practical manner.

Instead, inspired by the design of the case for the Spilsbury SBX-11 that was given to me by a friend, (similar to the one pictured on this page,) I decided to build a case for each radio, and one more for the battery. In addition to making it easier to pack everything, since it's easier to move several small boxes than one huge one, it also provides more flexibility. For example, if I'm going on a short road trip, I can take the 2m mobile and plug it into the car's power outlet instead of lugging around a bunch of extra stuff (battery, HF radio, antennas, etc,) that I won't need.

Well, I just finished the first of these cases. It's designed to hold my Yaesu FT-2900R 2m mobile radio. The box is constructed of 3/8 plywood, rabbetted and joined with glue at the seams. Inside the case are several ripped-down pieces of lumber which act as spacers, so the radio is held snugly in the case while allowing room for air circulation. There's a space behind the radio so the antenna cable has room to turn around and exit via the front opening without getting damaged.

The microphone hanger is attached to the lid of the case, so that the mic can be stowed inside the lid when not in use. The case is waterproofed, so it can be left out in the rain without risking damage to the radio. (The only thing left to accomplish this goal is to add a gasket to the lid seam.)

I've made the wiring connections as modular as the case design. The power cable is short, fused, and terminated with an Anderson SBS connector. It will be connected to a longer cable which will supply power from a battery, or a car's power outlet; using the Anderson connectors means I can build different cables for each power supply application, and interchange them between my radios. I'm also going to get a small extension for the antenna line so that I can connect an external antenna from the front, instead of having to remove the radio from the box each time I set it up and take it down.

With this setup, I can set up a station nearly anywhere, in only a couple minutes. It's even suitable for dropping into a vehicle to provide mobile service, as long as I don't have a front passenger. And while it's not as portable as my handheld, it also has fifteen times the output power, so I can see it being taken to a lot more places now that it has a nice-looking overcoat.

Chasing RFI: The Workaround

The only thing better than seeing a project through to its conclusion is not having to do the project at all.

I had been reading this document, which does a very good job explaining RFI, while I tried to find some time to hunt down the source of the interference in my house. While I was doing that, the good folks who brought us CHIRP made some improvements to the software that allow me to expand the squelch range on my Baofeng GT3, which meant I could cut out the bursts of static while still hearing actual signals.

"But hold on a sec," you say, "what exactly is this squelch thing you're talking about?" Squelch is a circuit in a radio receiver that turns off ("squelches") the audio when a signal is not being received. When a strong enough signal is detected, the "squelch is opened" - the audio circuit is turned on so you can hear the received signal.

Not all radios have a squelch circuit, but the ones that do (all that I've seen at least,) have an adjustment. This allows you to set the strength of signal that is required before the squelch opens. Ideally, you want to adjust the squelch to be low, so that you don't miss a transmission. However, there are times when you need to turn it up, such as when you're in an area with a lot of RF noise.

The problem with the UV5R series of radios (of which my GT3 is a member), is that the squelch is notoriously useless. Bursts of static will trick the radio into thinking that there's a signal present when there isn't one, and the squelch adjustment is very narrow (there is no noticeable difference between level 1 and level 9).

So, back to CHIRP. The 10 levels of squelch available in the GT3's menu (0 thru 9) are mapped to values inside the radio's programming. In fact, the radio can set the squelch anywhere between 0 and 127. At the factory, the 10 levels in the menu are mapped to these internal values.

Once I installed the latest daily build of CHIRP and looked at the squelch mappings on my radio, I discovered that levels 1 thru 9 (0 is mapped to 0, which disables the squelch circuit altogether) were mapped to values between 17 and 33, in increments of 2. On the advice of this page on the Miklor website, I changed the values to range between 24 and 64, in steps of 5.

After dumping the modified image to my radio, I moved to a part of the house where I previously had static. I turned the squelch up one step at a time until the static stopped. While I was doing this, a couple other folks were having a conversation on the local repeater that I was monitoring. I was able to confirm that my new squelch setting got rid of the static while still letting the signal from the repeater through.

So my time-consuming hunt for RFI sources has been called off. And a good thing too, since I have a bunch of other projects on the go, and I don't really have the time to go chasing RF gremlins.

Chasing RFI: Introduction

If you've been following along, you'll remember one of the reasons I'm building a portable RF shack is that my house is full of RF interference which is causing me problems. I'm going to try and track down the source of the interference, eliminate it if I can, and hopefully learn a bunch of stuff along the way.

Right now I'm in the very early stages of troubleshooting. Shortly after I got my handheld (a Baofeng GT3 Mk2) I noticed that it would break squelch in certain areas of my house while tuned to the local 2m repeater. When the squelch opens, all I hear is static.

My first thought was that some piece of computer gear was causing the interference, so one morning while everyone else was asleep, I tried to do some rudimentary investigation. I placed my radio in a location where it was picking up the interference, then I shut down my server, and cut power to my network stack. The noise went away. A little further experimenting pointed me to the ethernet switch.

However, changing the switch to a different model resulted in the same interference. Also, it seems that the interference is only present if there's an ethernet device connected to the switch.

A little later on, a friend of mine loaned me his SDR (software defined radio). I plugged it into my computer, installed HDSDR, and took a look at the waterfall display. I could easily see signals present all through the 2m amateur band, spaced at something like 30-50Khz intervals. Reading on the internet doesn't point me to any definite sources.

At this point I'm devising some more rigorous scientific testing so that I can conclusively narrow down the source of the interference. I'll post the results of my experiments here, so stay tuned.

Why a portable shack?

While I would love to have a fixed station in my house, I'm coming up with more and more reasons to forsake the basement radio room for a portable radio shack.

That's not to say that I won't use my radios at home, but I think I'm going to be doing more with the radios while out of the house than in it, and it's easier to accomodate the portable shack at home than it would be to take a permanent station on the road with me.

For starters, I don't have the space in the house to dedicate to a bunch of radio gear. While there are many places where I could set up a radio rig, they all get used for something else at some point. This means having a shack I can set up and take down easily is important, and then I'm halfway to a portable unit already.

Secondly, I don't have the space outside the house for a long antenna. We live on a city lot with neighbours on all sides. Our back yard is completely open; any mast would stick out like a sore thumb.

Thirdly, my house is full of RF trash. I'm going to do some work to narrow down the source and try to filter it out, (stay tuned for more on that,) but the simplest answer is just to get out of the house.

Of course, there are downsides to going portable. I'm going to be limited in power since I'm designing everything to run off a 12V battery. Since I'm not lugging a generator around, I'll be limited in the time I can spend on the air. I'm also going to be limited to portable antennas.

But then again, those limitations present some interesting engineering challenges.

The Router, Revisited

One of my readers asked for more pics of my router table hack, so here they are.

Here's an overall photo of the complete setup. Note the ad-hoc debris collection system. (the router cuts off bits of wood of various sizes, ranging from dust to large chunks.)

Here's what it looks like from below. The table surface is doubled up to bring it to the approximate height of the table saw table, and then a couple rails are added so the router table drops in between the rails of the saw table.

Here's a close-up of the table surface. I used a spade drill bit to provide a place for the bolt heads to drop in so they don't sit proud of the table surface. The hole for the router bit was cut on the drill press with a hole saw. It looks small, but there's no point in making it any larger as the router body stops me from using any larger bits anyway. The grooves in the table surface were accidental; I placed the router on the table surface to change the bit, and because I didn't use hardwood plywood for the table, the force required to break the chuck loose pressed the router body into the table.

A view from the back.