Archive for the ‘ham radio’ Category
Handiham World for 12 October 2011
October 12th, 2011 | 
Author: Welcome to Handiham World.
The temptation of power!
What is it about power that makes some people crazy for it? Once they have a taste of power, they want still more.
Of course in ham radio, the idea of more power is usually associated with operating with higher power output by adding RF amplifiers. If 100 watts is good, 1,000 must be better, right?
Wrong!
What does the FCC say? It’s §97.313, Transmitter power standards. Section (a) says, “An amateur station must use the minimum transmitter power necessary to carry out the desired communications.”
There are good reasons for using lower power levels most of the time. If the other station can hear you when you are using 100 watts, you are only wasting electricity to run more power than that. We are more conscious about waste these days, since power costs are going up and the generation of that wasted power wastes resources and causes pollution. Furthermore, that unnecessary power can cause your signal to be heard on adjacent frequencies and at long distances. A high-power station can easily cause interference to other users on the band, but there is also a much greater chance of RF getting into nearby conductors where it causes bad things to happen.
I remember a Handiham member who moved into an apartment and was lucky enough to be able to have a wire antenna installed on the roof of the building. Back in those days, we were able to field volunteers to help members with such projects, and our volunteer was able to install and connect the antenna. The fellow had moved from a private single-family house where he had owned and operated a complete, well-equipped station that included a linear amplifier for the HF bands. Our volunteer explained to him that the amplifier would not be practical in the new QTH, since there was not enough real estate to get the wire antenna well away from the building. The linear was stored in a closet, and the station was tested on the air with good results.
Well, you can probably guess what happened. The station’s owner was used to operating with high power. (Remember: the thinking was, “If some is good, more is better.) So out came the linear from the closet and back into the ham shack it went. It wasn’t long before we got a call with the bad news that the poor fellow had lost his ham radio privileges at his new QTH after setting off all the fire alarms in the building. I don’t know if he was ever able to get on the air after that. It was before the days of remote base internet operation, so he was probably stuck on whatever VHF repeaters he could work from his apartment.
Adding a linear can put enough RF energy into the area surrounding your shack to affect your neighbors, too, even if you live in a detached single-family home. Devices like audio amplifiers can be connected to speakers systems in home theaters by long lengths of unshielded wire. The final output ICs in these devices can act as rectifiers to demodulate the RF and cause loud thumping noises in the speakers. Other devices that may be connected to long lengths of wire are alarm systems, intercoms, and smoke detectors. The relatively weak field from a 100 watt station might occasionally affect something in one’s own home, but is seldom a problem next door. Bump the power up to 1,000 watts and you are asking for trouble.
Another consideration is the need for an RF safety audit. Generally speaking, you don’t have too much to worry about when using the typical transceiver without an amplifier. When you increase power levels beyond that 100 watts you are going to need to “run the numbers” to make sure that you are in compliance with RF safety rules. For example, if you are using 100 watts on 29 MHz with a dipole antenna, you will be in full compliance at a distance of 25 feet from the antenna for both controlled and uncontrolled space. However, if you use 1,000 watts and the same antenna, you are out of compliance for uncontrolled space. If a neighbor’s property is within that 25 feet, you are now operating outside regulations and exceeding safe power levels. It is even worse if you have a beam antenna for 10 meters because of the antenna gain, which could increase the RF exposure even more in the uncontrolled space. It goes without saying that you want to keep RF exposure to yourself, your family, and your neighbors to safe levels. It is much easier to do this at lower power levels.
My favorite reason to stick to lower power levels is that linear amplifiers only give your transmitted signal a boost. They do nothing at all to help you receive weak signals. In fact, calling CQ with your linear turned on can lead to responses from stations that are too weak to copy. You can get more bang for your buck by installing a better antenna system. Once I learned this for myself, I have advised new hams to concentrate on good, effective antennas instead of amplifiers. After all, the antenna system will help pull in those weak signals, helping you both on receive and transmit.
There is a time and a place for turning on the amplifier. It is when band conditions are deteriorating and more power might help you complete the QSO. It might be when you are the net control station on an HF net and it is necessary to use high power to make sure that you are heard throughout the geographic area of the net. It is probably going to be helpful in the summer when there is thunderstorm static and you are operating on 75 meters. But more often than not high power is really not necessary. Let’s not use it if we don’t need it.
For Handiham World, I’m…
Enough Planning! It’s Time to Put This Antenna Up!
Hopefully Monday will be an antenna-building day. I don’t know that it will all come together in one shot, but if I don’t get this project going it’s never going to get done.
I spent some time in the hardware store yesterday, picking out the many different bits and pieces that I’ll need for the job. Hard to believe how much it all added up to. Gulp! At least I had a coupon for $10 off of my purchase. As it is there are still a couple more little things I need, but I’ll have to drive up to Willmar for those on Monday.
Here’s a rough sketch that I made last March, dusted off and updated slightly. There are still a couple of unknowns — those are the figures in red.
I’m not certain that I’ll need to attach anything to the adjacent church-building, since I may get away with just draping the wire in a nearby tree. But I’ll figure that out as I go. I’ve planned enough! It’s time to put this antenna up!
Of Pounding Ground Rods and Labeling a Field Box
My arm is tired! I pounded in a ground rod tonight, a stout 8-footer from Fleet Farm. It wouldn’t have been so bad if it had gone in on the first try, but it took me three tries before I found a spot that didn’t have some obstruction about four feet under ground! (Remember I live in Granite Falls. There’s lots of rock around here.) I’m not sure which was harder — swinging the sledge hammer until the rod got stuck, or trying to pull the crazy thing out of the ground when it did. Soaking the ground with water helped to get it out in one instance.
It’s tempting to soak the ground with water before pounding your ground rod in, to make it sink in easier, but I’ve read that you shouldn’t do that as you wind up with a poor connection after the soil dries. As with many other things, the easy way isn’t always the best way.
Anyhow, I finally got it in far enough. There’s about ten inches sticking up out of the ground still, but all I’m doing by swinging at it now is flattening out the top. Once my wife hides it with a hosta plant it will look just fine! I tried pounding in a second one, but when it got stuck and I had to work it out (by clamping vicegrips on it and prying it out with a crowbar, a few inches at a time), I called it a day.
Much easier and more satisfying was labeling the toolbox I’ve converted into a field-kit:
I’m asking an awful lot of this decal, sticking it on a pebbled surface. But so far it’s sticking just fine. Randy George, N3ZK, does a great job on these, ships them fast, and the price is right! For only $4.00 (shipping included) you get three of these labels.
In the field box right now is my Heathkit HW-8 and all the accessories necessary to zip out to my picnic table and get on the air with my low-hanging, temporary OCF dipole. Pretty soon it will be too cold to do that comfortably! That’s why I’m pounding ground rods, trying to get my long-awaited New Carolina Windom up and going before the ice and snow comes.
Handiham World for 05 October 2011
Welcome to Handiham World.
A broken water pipe gets me thinking…
What sort of things might cause a disaster in my ham radio shack? I started thinking about this recently after dealing with a minor disaster caused by a leaking water pipe in the ceiling of the basement. As usual, I was sitting in my home office, which also serves as my ham shack, when I heard a faint drip, drip, drip. Since I spend an awful lot of time in my office, I know and recognize all of the usual sounds of the house around me. In fact, I don’t really notice if the compressor in the freezer comes on and my brain rarely even registers sound of the washing machine or dryer in the adjacent laundry room. The furnace or air conditioner can come on and go off without interrupting me. Jasper, my dog, wanders the house and occasionally growls at a squirrel that he sees through the window. None of this stuff bothers me or particularly gets my attention. But the brain is a marvelous thing; it can ignore the common and expected while immediately picking up on something unusual.
The sound of dripping water, even though barely audible, got my attention!
Sure enough, an inspection of the recreation room around the corner from my office revealed a drip from the ceiling. Several of the tiles in the suspended ceiling had gotten waterlogged and collapsed onto the floor, and I hadn’t heard that sound because I had only just a few minutes before come into the office to sit down and do some more work. The leak must have occurred in the afternoon shortly after I had finished my usual office day and had taken the dog out for a walk. When I returned to the office after dinner, that’s when I heard the dripping sound that was so out of place. It turns out that a 90° copper connecting joint in the cold water pipe going to the outdoor irrigation system developed a tiny pinhole leak on the inside of the bend. The tiny, almost invisible spray was enough to create quite a mess given a few hours. The soaked ceiling tiles collapsed onto an easy chair, soaking it and ruining the cushion. The carpet on the floor was soaked in an area of about a yard square. A few other items stored in the room got wet on the outside, but were not ruined because I heard the drip and responded in time to shut off the water. Fortunately, we have a carpet cleaning machine that vacuums up water and we had a spare cushion for the chair. I haven’t replaced the ceiling tiles yet, but they are standard 2′ x 2′ squares that are commonly available at any big box building store. As we are so fond of saying in Minnesota, “it could’ve been worse!”
Of course I called the plumber, and he was able to fix the problem the next day. Fortunately, we have a shut off valve for that particular leg of the water system in our house, so there was no need to keep the main valve turned off. It’s heck to be without water when you need to wash, cook, and flush! But what got me to thinking about the ham shack in relation to this broken pipe was that the shutoff valve is located directly above the ceiling in my office. In fact, several water pipes converge in the ceiling above the ham shack and it is sobering to think that the copper pipe carrying all of that water is exactly the same age as the pipe fitting that failed in the next room, which is about 20 years old. So, as I sit here talking into the microphone and enjoying a nice session on my radio, will I one day feel a drip, drip, drip on my head? I guess it could happen, and I have to admit that when I finished the basement and built the ham shack I never gave a second thought to the water pipes running through the ceiling joists overhead. I had grown up with copper water pipe in my parents’ house, and I cannot remember a single time that there had ever been a leak. I guess I would not have been too surprised if a leak had occurred where pipes were joined in the soldered connection, but to have a piece of copper simply spring a leak in the body of the pipe? It did seem pretty unlikely, but like all such things it is not something to worry about unless it happens to you – and it happened to me!
So I am forced to assess the probability of another leak, perhaps occurring over the critical electronic and computing equipment I have in the ham shack. Some of this equipment runs for hours or days at a time without being turned off. One can only imagine the damage that would be caused by water pouring onto the energized equipment. When I wired the ham shack, everything was put on ground fault interrupters. Given a good soaking, the equipment would probably short and trip the interrupters, but by then of course the station and computers would be ruined. This is not something I care to think about, but it is nonetheless a possibility. I had considered the possibility of a leak like the one we had to be extremely remote, and perhaps I was right. Nonetheless, had the leak occurred over the ham shack it would’ve meant many thousands of dollars of damage instead of a soaked chair cushion and a few feet of wet carpet.
What to do? Well, moving the ham shack and home office would be a major undertaking and a huge disruption in my work schedule. It wouldn’t be impossible, but it would be expensive and difficult. For now, the best I can do is to turn the main water valve for the entire house to the “off” position whenever we leave on vacation or for any kind of extended multi-day trip. This is something I have always done anyway, and while it is not a perfect solution, it does prevent damage from leaks that might occur when no one is home and when damage can be severe due to the fact that no one is around to discover the leak. Long ago, when I worked in an appliance store, we recommended that our customers who were leaving on vacation turn off the water supply to their washing machines because the hoses that fed the washing machine might burst and cause flooding in the basement. Turning off the whole house valve takes care of that problem. Keeping equipment off the floor is another good idea.
We are used to thinking about protecting our amateur radio equipment and its associated computer equipment from lightning damage, but we cannot ignore the threat posed by water!
For Handiham World, I’m…
Central Florida QRP Meetup 8 October 2011
This coming Saturday at the Melbourne Hamfest and ARRL FL State Convention QRP ops from around the state will gather for a time of eyeball QSO’s, bragging, show ‘n tell and maybe even some operating from the picnic tables in the park next door!
Looking for Something?
Get there early and do your tailgating and swapping so you can gather at noon near the front entrance. Look for K4UPG’s gawdy yellow hat and come up and say HI! Some of us want to go to lunch together and depending on the number we have a couple places in mind that are nearby the event site.
So come one and all (even the curious) and join the fun.
GATHERING: Front entrance to Auditorium
DATE: Saturday, 8 October 2011
TIME: 12:00-12:15 EDT
Bring some gear if you want to play radio in the park or on the beach later in the day!
Handiham World for 28 September 2011
Welcome to Handiham World.
What got you started in radio?
When I think about that question, I recall a little crystal radio kit that my dad bought for me. It had a plastic housing to make it look like a real table radio, except that it was smaller and had only a single earpiece. And of course it “magically” took a radio signal right out of the airwaves and turned it into music without any electricity at all! It was one of several crystal diode radios that I had as a kid. Another memorable one was made up in a round plastic ball that was supposed to be a satellite. There was a tuning control that consisted of a slug-tuned coil. The brass screw from the ferrite slug extended out of the top of the “satellite” like some sort of antenna. It had a little rubber cap on it to serve as a grip, so that the coil could be tuned more easily. The real antenna was a piece of bell wire with an alligator clip at the end. That allowed you to connect the radio to something conductive that might hopefully act as a better antenna and bring in a local AM station. Of course today the term “satellite radio” means something completely different!
When I was a teenager, dad bought me a Knight-Kit Span Master two tube regenerative receiver. It was not my brightest moment in radio when the kit manual called for putting “spaghetti” over some of the bare wire leads during assembly and I went down to the kitchen cabinet to find this apparently necessary but odd ingredient for a radio. Dad straightened me out on that and we ended up using the insulating tubing that was actually already provided by Knight-Kit.
Image: Here is the Knight-Kit Span Master as shown in a 1962 Allied Radio catalog. You could get the outdoor antenna kit for only 1 cent more, but the radio itself cost $25.95.
The Span Master worked when it was finished, so I installed it in the vinyl-covered wooden cabinet that came with it and ran a wire out of my bedroom window to serve as an antenna. The circuit might not seem like much, since it had only two vacuum tubes, but it turned out to be light-years ahead of the crystal radios. One important feature was a speaker, so I didn’t have to use headphones. The tuning knob was connected directly to a variable capacitor, but there was a helpful bandspread knob connected to a second capacitor so that fine tuning was possible without pulleys and dial strings. Furthermore, the radio had a band switch and covered not only the AM broadcast band but also several short-wave bands. In spite of the two tube design, a fair amount of gain could be had from the simple regenerative circuit. It was also possible to hear Morse code and even something that was new and mysterious back then: SSB. You had to be patient and careful tuning it in, though. It was more fun to listen to far off short-wave stations and find out what was happening all around the world.
I consider the Span Master to have been the radio that really got me interested in getting my amateur radio Novice license. Today we can still find electronic kits, and who knows? One of those kits might spark the interest of a future engineer, scientist, or teacher! Consider an electronic kit as a gift for your child, making it age-appropriate, of course. Then make it a parent-child project to assemble it and make it work. You will both have fun, and open the door to STEM: Science, Technology, Engineering, and Math.
Next week: Thoughts about a broken water pipe.
For Handiham World, I’m…
