I keep hearing things from other Hams that just don’t ring true.
Over the years, yep been a Ham for about 44 years now, I’ve found that there’s good reason to question conventional wisdom. Perhaps there’s something about the hair on the back of my neck, or perhaps it’s really a good indicator that I should take a second look.
So, below I list some things that just rub me wrong. Feel free to tell me if you don’t agree, or send me additional Ham Myths I should look into.
A while ago I heard about something called “NVIS”, “Near Vertical Incidence Skywave” communications. The word was that NVIS would let you communicate reliably up to some 300-600 miles on lower HF bands at any time, day or night. That sounded interesting, so I thought I’d learn more.
Not too long after that, I mentioned this to some other Hams and was told that was nonsense because everyone knew that HF kind of comes and goes. They knew from experience that once you get past ground wave on HF, which isn’t that far, all you have left is “Skip” that rarely works well over those shorter distances. It was also explained to me that the frequencies I was talking about were so far below MUF that there would be absorption and the signals would be weak and useless.
Well, guess what. I picked up what’s called an AS-2259 antenna, which is designed for NVIS type of communications and took it to Field Day with my 20W military radio. In the middle of the contest I set it up and tried it out on 40 Meters in the middle of the day. For a while I thought there was something wrong with the antenna because most of the signals were relatively weak. Tuning around I started to hear various stations with strong signals and completely clear. After a while I realized that all the strong signals were withing some 600 miles, so I started to work them with my 20W radio, one after another. Then I started asking them what they were using for antennas. Virtual all of them were on relatively low horizontal dipoles–antennas that send a lot of signal straight up. Ahhh, the light goes on.
So, I went on a quest to learn more and to look at using this for disaster support communications. It turns out that NVIS did work reliably–nearly any time day or night you can work stations reliably, using the right kind of antennas and the right band between 160M and 40M. The nice thing about it is that it provides reliable communications over hills, in valleys, through foliage, and with low power and easily portable antennas. It’s a perfect replacement for repeaters when they aren’t available. In fact, NVIS can easily get places repeaters have a hard time reaching.
I keep hearing from Hams who haven’t seen this work and who “know from experience” that you can’t do reliable communications like that. Seems like the word is taking a while to get out even though NVIS has been used for years.
Now for extra points find out why this works and why the signals are so strong!
How many times have you heard Hams refer to an “RF Ground”. It’s as if there’s some mythical connection to which you can connect and that will magically absorb RF and dispense with it in a way that affects nothing else.
What I really find surprising is the “lengths” (literally) Hams will go to connect their stations to these magic RF grounds. It’s as if the laws of physics that govern RF and conductors are suspended when you call it a “ground”. Simply connect a copper strap or heavy gauge wire to this “RF ground” and stray RF is a thing of the past. Never mind how many wavelengths it is to that single 8′ ground rod or how much inductance there is at the operating frequency.
Hey, it’s an RF Ground!
How many of us would spend good money and time to setup an antenna and only bother to do 1/2 the job? Well, it seems that many of us do.
Enter the “counterpoise”. It’s the “other” half of many antennas you don’t have to worry much about–right? Just make it about 5% longer and toss it out on the ground (earth this time guys) and you’re set, right? — Wrong.
The ugly stepchild of many an antenna is actually part of your antenna, so don’t insult it by calling it a “counterpoise”. That part of your antenna will contribute loss, affect your antenna’s pattern, and will inject noise into your receiver.
Let’s all honor the dignity of both sides of our antennas!
Nope, I didn’t miss anything in the name of this section. The “Half-wave End-Fed” antenna is really a myth in and of itself.
You’ve seen the adds and heard the claims–you don’t need a counterpoise (there’s that word again) with this type of antenna because it’s fed at a “High-Z” point on the antenna. It’s as if the minimal current at that point in the antenna negates all good sense. If you think there’s nothing on the “back-end” of the antenna feed-point, why do you even bother with the antenna at all. Hey, it’s a “High-Z” point in the antenna!
If you haven’t sorted it out by now, let me spell it for you. There is no such thing as a “Half-wave End-fed” antenna because you simply can’t feed it against nothing. Since you need something more than nothing, the antenna is more than just a half-wave length of wire. If you think it’s Ok because it’s High-Z, then what the heck is the deal on the “antenna” side of that feed? Same rules apply!
So, should it be called a “Half-wave and a Half End-fed”, a “Half-wave and a bit more End-fed”, perhaps a “Half-wave and a quarter End-Fed” (or is that really a “Half-wave End-fed and a quarter)”?
Remember that “counterpoise”? If you still think there’s really a functional “Half-wave End-fed” antenna, then read the part about a counterpoise above.
(Half-Wave End-fed epilogue)
I know, you know people who have been using these antennas for some time and perhaps you’ve used them yourself. You know it works and you’re convinced I’m all wet on this because you don’t have any more antenna than that. Well you do, it’s your transmission line, your radio, the power cable connected to it, and even YOU if you’re holding the microphone or the radio. But wait (I love that), you have a common-mode choke or balun at the antenna, so what does the transmission line have to do with it? The answer is simple, it’s (you guessed it) that very High-Z that seems to make it a magic antenna that’s convoluted your intent to isolate your feed-line. I’ll let you sort it out.
If I hear one more Ham say “Antenna tuners don’t really tune antennas, they just make the radio think it’s OK”, I’ll scream. If that was the case, then the same is true of the loading coil at the base of your antenna (or perhaps in the middle) and of the tank circuit at the output of your tube amplifier.
Oh, but those are different situations you say. Really? So if I put a shield around that loading coil at the base of the antenna does that now mean it’s not really affecting your antenna? If I move it a few inches or feet away from the antenna elements is it really something different? If I move it all the way back to the transmitter, is it now something really different? You make the call.
The key is in the transfer of power and matching the source to the load (antenna). If you ever adjusted the Load and Tune on your amplifier while watching a power output meter you know what I’m talking about. If all antenna tuners do is make the transmitter happy, then tell me why the amp’s tank circuit isn’t an antenna tuner.
OK, perhaps the term “antenna tuner” is a problem. Might be better to call it an “antenna system tuner” or a “complex impedance matching device”. But then Hams like confusing terms (grounds, counterpoises), so what the heck!
Here’s one I really don’t understand, and it involves more than what the title implies.
The statement usually comes something like this. “Don’t forget to ground everything to the car chassis including the antenna and radio.” Really? Why would one do that?
When I ask that question often the response relates to chassis being the best ground in the vehicle or something about being the closest to the actual ground under it. The problem is that doing this violates all the basic principals at work in a Ham station.
Sure, the chassis might be a good DC ground but that really doesn’t have much to do with RF, does it? If you’ve read some of my comments above, you already know that I advocate RF staying at the antenna where it can radiate. So what does running a ground wire from the antenna to the chassis accomplish when it has length, has inductance, and presumably has current? I’ll tell you what it does, it creates an additional RF path and radiator that becomes another part of your antenna and does so in an unpredictable way and therefore may actually impair operation. It also encourages RF to flow on the chassis and everything the “ground” wire passes and therefore to couple into other cabling below the vehicle.
Next, what does grounding the radio to the chassis do? It provides yet another means for stray RF to find a way into the inside of the vehicle and to the body of your radio. Why would anyone want that? It does this in ways that are highly unpredictable because with RF everything changes with frequency. Things could be perfect for weeks, months, or years, but then all of a sudden there’s problems. Could it be that the operator hasn’t worked that frequency before?
What to do, what to do… The first thing is to consider what constitutes the antenna. If you have a whip antenna of some sort, the vehicle is the other half of your antenna (and it’s an active half at that). What part of the vehicle do you want to be that part of the antenna? Unless you have a sporty fiberglass go-fast car (in which case all bets are off), it’s the outside of the vehicle body. That, along with the whip, is where the RF should go and from where it should radiate and not cables running around pretending to be “grounds” and the things to which they connect.
My advice is to make sure as much of the outside of the vehicle is bonded together (for RF), that the coax feeding the antenna is terminated is some way to the OUTSIDE of the body, and that any other cables running away from the antenna or near it have chokes to prevent RF from doing nasty things. That includes the transmission line and antenna control lines where they leave the antenna and the power cables for your mega-power after-market driving lights (or for some hams, extra emergency flashers). And where those cables enter the vehicle, please… please… please put chokes on them to keep the RF out of the vehicle.
One last note on connecting the coax shield to the body. Try to do that on an OUTSIDE surface and definitely don’t run that ground down into the trunk to tie onto so nice spot INSIDE the vehicle. If you ask why, you’re not listening. I know, it’s sometimes hard to do that without putting a big ground bolt through the paint on your fancy new car, so look for things like luggage rack mounts or perhaps even something on the body lip just under the edge of a trunk or door and MOUNT YOUR ANTENNA THERE!
Now for the test question:
When is a ground wire not an RF ground? … When it has length and there’s current!
Here’s one I’m sure you’ve heard and probably repeated to others. It seems to make sense on the surface, so it’s rarely challenged. However, doing this can not only be hazardous to your equipment, but to your own safety. It’s the old “Run a wide copper strap out to your ground” myth.
The apparent basis for many hams saying that you should run a wide copper strap or other large low-loss conductor from your station out to some ground outside is apparently it’s magic ability to conduct all the nasty noise and lightning energy outside and dispense with it.
If you read my diatribe on RF Grounds above, you may be able to infer what’s coming in this installment. That RF Grounds section above is really about dealing with stray RF around the shack. Here we’ll talk about a much more serious situation–lightning strikes.
So, why is it that people get the idea that you need to conduct lightning energy from your station to a ground outside? I suppose if the lightning were to come down the chimney into your house and directly hit the equipment in your shack that you might want to conduct that energy somewhere else. Of course if that unlikely scenario actually happened, it would be due to some other serious transgressions and you’d have much more serious problems.
The much more likely situation, I should hope, is that lightning will hit something outside, like your 70′ tower with 21′ dual-band whip on the top. When that happens, the last thing you want to do is to invite it inside. That should be obvious. So why then would you install a low reactance conductor from your antenna ground outside to your equipment inside?
(I also want you to think about the length of such a conductor and what that means for RF and lightning, but I’m not going to waste space getting into that now.)
Now we get to the crux of this matter–what you really want is to keep lightning energy outside. This means doing things to minimize the likelihood that it would follow conductors into your house. And, we have lightning to thank for the answer. Much of the energy of a lightning strike is in the form of a very fast and sharp pulse and it therefore behaves much like RF.
At this point I’m going to ask everyone who has a thought on how to keep that energy outside to raise their hand. — Great, we have at least half of the audience raising their hands. And the answer is… Wait for the drum roll… Add reactance to your conductors!
So, now we’ve done it. We managed to pretty much piss off nearly half of the Ham lightning protection experts who’ve been advocating heavy metal to draw the energy out of your house. But we did gain a few converts who are now feverishly conceiving of ways to reduce lightning energy coming in on their coax and control cables. Yes, coiling your cables before they enter the house can help, but think about how the coils should be wrapped to keep the energy from simply jumping across them. OK, burying cables is also a good idea. Yes, sharp angles add inductance, and the really smart person at the back of the room is considering tubular conductive chokes (he must have attended the advanced class already).
Yes, I know, commercial installations use heavy copper straps from building entrance panels to the antenna ground, to the fence around the tower, to just about everything. But most of us don’t live at a commercial tower site and we’re not about to tear our house down to build a hardened communications facility with a proper Perimeter Ground system. OK, there are a few.
And what did I not tell you that’s very important in this discussion? I didn’t tell you how you have to do something more than an 8′ ground rod for your lightning ground (sorry — if it the energy can’t get to earth ground it may very well visit your house). I didn’t mention that you will still have some energy following your cables into the house (sorry — and you do need to account for this). I didn’t even bring up “Single Point Grounds” (sorry — and don’t assume you know what that means as it has nothing to do with an Earth ground).
Oh, and one more thing for those who think they have me because they ran that heavy copper strap to a separate ground (not their antenna ground). All I can say is that the lightning will appreciate yet another path to follow and more conductors with which to do magic.
If I got you thinking about why you may not want those large copper straps, then I’ve done my job, but it’s only a start. Stay tuned for future noise from me on this topic and more reasons for the grounding experts of Hamdom to send me hate mail.
It’s been brought to my attention by some people that RACES is a national Amateur Radio organization of some sort. … Really? I didn’t know that.
So, for those who think that is the case, identify the national director for RACES and where their national office is located. … I didn’t think so.
For extra points, try to determine if the following are also national Amateur Radio organizations or societies… ARES, MARS, SATERN, CAP. If not, then double your points by describing what they actually are.
Good luck on this challenge and let me know if you figure it all out.
Well, perhaps that’s right some times. Frankly, I don’t know anyone who hasn’t spun a line or tried to fudge their way through something. That’s human nature, but out of respect for others, we should try to always be honest about what we know.
About the only place you’ll see any significant biographical information on me is perhaps on my Facebook or LinkedIn pages. I don’t have a zillion lines in my E-Mail signature touting my every accomplishment because I consider that to be rude. I believe my comments should stand on their own merit in whatever forum I make them. I also try to evaluate the comments of others without prejudice. Anyone, even someone who irritates me to no end, can have something valuable to say. It would be my loss if I discount their input and miss something of value.
So, if you think I don’t know what I’m talking about, as I’ve been told by some in the past, then feel free to ignore me. If by some miracle a gem of knowledge comes from my rants and you miss it because you think I’m a jerk, then that’s your loss. But please, respect others by letting people come to their own conclusions on what they want to believe and don’t discount their passionate debate because it challenges your perspective.
In case you’re interested, I didn’t graduate from college. I was one of those people who felt compelled to learn things on my own and was rarely satisfied running at the pace of others, whether that be faster or slower. At times I needed to jump forward and at times I needed to know more. Because of this, formal education was always difficult for me. I did, however take college electronics classes in High School. My high school had nothing like that for me, so a couple times a week they would let me drive to Oakland Community College to take courses.
After a while I did go to RETS in Detroit, which was a great experience for me. I found friends there and instructors who were willing to put up with my picking something apart ad infinitum or completely blowing something off that I didn’t find important to know. I did irritate some of them at times, but in the end, I think we all parted respecting each other.
Early on I worked for a strange and jovial guy named Gary Schmidt, who had a small company called Audio Services Incorporated in Detroit. We did broadcast engineering and predictably I managed to irritate Gary’s chief engineer, also named Chuck, time and time again with the things I’d come up with or minor stabs at why he couldn’t figure something out. I’ll never forget one of his most infamous statements, “Nobody will ever need a microprocessor more powerful than a (Intel) 4004.” Eventually, I was banished to WDRQ radio in Detroit as their chief engineer. It was a top 40 rocker (yuck) and of course I worked with some very interesting individuals, including a talented engineer and musician name Pete.
My real career started at Applied Research Labs working on spectro-chemical analysis equipment as a field engineer covering 5 states. I worked with a mix of X-ray florescence, optical emission (electric discharge), and inductively-coupled plasma analyzers (RF). I did have training with their scanning electron microscopes and scanning mass spectrometers, but never really worked on them much. That job ended up taking me to fun places like Mexico, England, Switzerland, Venezuela, Brazil, and Lynn Lake Manitoba–some 1000 miles north of here in the middle of February.
For the last 18 years I’ve been running an Internet company that provides connectivity to a number of public institutions in Northern Michigan as well as a mix of offices and individual users. We also build, host, and maintain Web sites for many of Michigan’s larger (and smaller) tourism destinations (do a search for “Gaslight Media”). In addition, we build “campus style” mixed fiber, copper, and wireless networks for a range of customers. I’m the owner and also the chief programmer responsible for our on-line reservations systems and more recently event housing, registration, and management systems.
My familiarity with programming and computers for some 30 years runs from C to PHP and PCs to servers and routers. I generally work in PHP, HTML, CSS, and SQL (Postgres). I don’t claim to know it all, but frankly my more recent projects have resulted in rather reliable, extensible, and manageable code.
On the Ham Radio side, I’ve been a Ham since I was 16. That’s, aaahhh, some 45 years now. I’ve seen a lot and I keep learning things about radio, communications, and electronics, particularly from my good friend Jim. The one thing about that experience that stands out the most is that I learned never to judge anyone’s comments on anything other than each comment they make. If you try real hard to irritate me, as some have managed to do, I may just walk away and ignore you for a while, but am always willing to work with you again in the future.
So, please, if you think I don’t know what I’m talking about, feel free to challenge anything I say. If you do, please also have the respect and courtesy to do so in my presence or direct to me in E-Mail or on the various discussion groups I frequent. Also come prepared to offer a rational and supportable alternative perspective and don’t be offended if I press you for more.
We can all learn a lot engaging in civil discourse and respect. I can assure you that I’ll try to follow that advice myself. But please don’t just discount my comments without due consideration.
I occasionally hear people say that PowerPole connectors can’t be connected backwards. While that may be true, they can in many cases be connected offset. What happens then depends on which way it’s offset and what’s connected to them.
Consider the picture here of a pair of 70A PowerPole connectors plugged together offset. Normally one wouldn’t do this, but there are situations where it can happen–perhaps when you can’t directly see it or you’re otherwise diverted. While I haven’t actually done this, I almost did in my car with my hands way up under the dash and barely visible. I did do it, with power applied, in another situation.
That situation was while I was testing a radio on my bench. I have a RIGrunner PowerPole outlet strip at the right front of my bench. I reached over to plug the cable from the radio in and, not paying enough attention, I didn’t quick make it far enough. The result was a quick flash from the associated fuse and the immediate realization I screwed up.
So why did the fuse blow? The black (-) from the radio was plugged into the red (+) on the outlet strip. Since the radio was connected to my antenna switches at the time, and therefore grounded to my station ground, it all provided a nice path from + on the outlet strip right to the station ground. Having proper fusing in the line is a good thing.
You might be wondering then what’s the big deal if you have fuses. Well, if you’re connecting to a high-current source and expecting the fuse in the red (+) lead of your radio’s power cable to blow, do you think it will do that? This is why many radios now have fuses in both the positive and negative side of the power cable.
I do like PowerPoles and use them all over the place, but one does need to consider how you could mess up.
There are of course other “Ham-isms” for other areas of Hamdom rolling around in my head. I’ll add some more here as time permits, but the couch is calling to me. So are some people on the radio, but there’s one basic law of Ham radio most Hams don’t know — You don’t always have to answer when someone calls you on the radio!
Chuck – N8DNX