The latest edition of the Flying Pigs QRP Club Bacon Bits Quarterly (BBQ is now online! This issue includes articles on the following topics:
Dan, AC6LA, has a new domain name, http://www.ac6la.com/. On the site, there is a variety of software, including some programs that are free:
TLDetails and MoxGen are self-contained, the others require that you
have Excel 97 or later already installed.
TLDetails looks really interesting to me.
I not only use this blog to keep track of the things I do in ham radio, but to also note interesting things that I’d like to pursue someday. I refer to these things as “one of those projects.”
The AMRAD Active Antenna is an active E-Field probe has proven to be simple and effective. AMRAD has tinkered with an earlier design to improve performance and created a set of printed circuit boards. A construction article appears in the September, 2001 QST. The AMRAD page contains some additional construction information to this web page to help in the construction.
This antenna is more than an LF antenna. Frequency response curves in the article show the response to be flat out past 10 MHz.
On Wednesday, I had the pleasure of helping Colin KD8CCQ, a new ham, get set up. He had purchased an IC-706 and an SG-239 Smartuner, but was having some trouble figuring out how to hook it up. I didn’t see the manual, but according to this guy, it wasn’t much help anyway–at least not to the new ham.
Over the course of an hour or so, we discussed various antennas that he could set up, using the tuner, such as a long wire and a doublet (center-fed Zepp). He has a great setup in that he lives in an older neighborhood, and has two big trees more than 100 feet apart that he could use to support the doublet at 40 feet or more. He wasn’t sure that his wife was going to go for that, but I suggested that this really would be his best bet, and after a couple of months, she won’t even notice it.
It didn’t occur to me to search for information on the SG-239 on the Web. (Why I don’t know–there’s almost always a ton of info on just about any topic on the Web.) I did so this morning and found the SG-239 Antenna Coupler Tutorial.
What a great site! The site contains original material by Dave N9ZRT as well as links to other sites that describe applications of the SG-239. There are discussions of the various types of antennas to use with the tuner as well as how to build an inexpensive weatherproof case for the tuner.
Unfortunately, Colin does not yet have his General Class license, so he can’t do any transmitting, but he did set up the tuner and rig to do some listening. I got an enthusiast e-mail titled “Wow!” from him this morning, in which he exclaimed,
I wired things up upstairs last night while I was watching the game, threw a piece of wire onto the antenna tuner, switched the radio on 5 minutes ago and immediately picked up FM5BH who, as far as I can tell, is operating out of Martinique, South America! This is so cool!
Cool indeed–for him and for me.
On the Elecraft mailling list, Jess AE0CW (how’s that for a great call?) asked where he could find a trial version of some antenna modeling software. Someone replied that EZNEC offered a free demo package.
This morning, Dave G3YMC suggested that he look at MMANA, describing it as “free and excellent.” There’s even a mailing list for user support.
I haven’t tried it yet, but it does look like a good program. Antenna modelling is one of those things I keep threatening to get into. Maybe with this program, I’ll actually do it.
When I started teaching the General Class license course a couple of years ago, one of the things I needed to learn about was RF safety. Back in the old days when I got my General (1971), I don’t recall having to answer any questions on this topic at all.
As I’ve mentioned before, all that you need to know can be found in FCC OET Bulletin No. 65, but while the information may all be there, using it is another matter. Well, to make RF safety more practical, the University of Texas ARC offers an online RF Exposure Safety Calculator. The program calculates the RF power density in the main beam of an antenna.
All you need to do is enter the power being supplied to the antenna, frequency, an antenna gain factor (2.2 for dipoles), and distance from the antenna to the area of interest. The program then calculates the RF power density of this arrangement, compares it to the limits, and tells you if you’re safe or not. It will also tell you how far away you have to be to be safe. Very cool.
Jerry Sevick, W2FMI, is the author of the amateur radio classic, Understanding, Building, and Using Baluns and Ununs and the more engineering-oriented, Transmission Line Transformers. He’s done more to take the black magic out of baluns than anyone in ham radio, and I was pleased to hear him speak at this year’s Dayton.
He recently published a series of articles on the topic in the trade magazine High Frequency Electronics. They’re all online and all worth reading:
There’s lot of other good stuff on the High Frequency Electronics website, too. The editor, Gary Breed, K9AY, is a well-known amateur radio operator, and there’s lots of good stuff there for guys like us, even though it’s really aimed at RF engineers.
On the Elecraft mailling list, there was a thread recently discussing portable antenna insulators. One guy noted that he scrounges Lexan scraps and makes insulators out of them, to which Mike VP8NO replied,
Seems like overkill to me. By using synthetic “string” to tie off the ends you have all the insulator you need. OTOH I use plastic “corks” from wine bottles on the end of the elevated radials of my 30 metre GP, microwave oven tested naturally. Much more fun to collect than Lexan scraps.
I e-mailed Mike and asked what he meant by “microwave tested.” He answered:
The idea is to test insulators/dielectric material by putting them in the microwave oven along with a mug of water to provide a load. The water should boil but the dielectric under test should stay cool indicating a good low loss rf material. I have noticed a growing take up of plastic “corks” in mid price range wines from VK, ZL, CE and ZS. Never had a bad bottle failure with one. Cork “corks” on the other hand, depending upon quality, have anything up to 5-8% failure rate. I guess not all natural cork is created equal and poor quality just lets air through. Contrary to expectation the UV doesn’t seem to kill them too quickly either.
Makes sense to me. I’ll have to start some of my own, errrrp, research.
On the G4FQG Software page, R.J. Edwards says, “There ARE such things as free lunches,” and then goes on to prove that point by offering a bunch of “original, high-quality, radio engineering/modelling programs” for nothing.
There’s lots of good stuff here, including programs that will help you model and design:
One of the cool things about these programs are that they’re all DOS programs, and the downloadable files are all small .EXE files that you can run directly after downloading.
Antenna modelling has been on my list of ham radio to-do list for quite some time now, but I’ve been putting it off because getting into it usually means downloading a complicated program with a relatively steep learning curve. With these simple programs, I may actually get around to doing it. The one I’m most interested in at this point is VERTLOAD, which models base-fed vertical antennas with load coils at any height.
About a year ago, I bought a “bullet weight” from Radio Works for getting lines up into trees. The weight has a hole through the center, through which you thread the rope or the wire or whatever. The problem, of course, is what happens when the line gets snagged in a tree?
This happened to me about three months ago, and no amount of pulling on the rope was going to get it to come down. In fact, what happened is that the rope broke, and now the weight is stuck up in the branches.
Recently, there was some discussion on the Elecraft mailing list on how best to do this. To date, here’s the best response:
From: tjmc
To: Alfred Lorona
Subject: Re: [Elecraft] antenna wireIf you must sling a weighted wire into a tree, use a fishing weight. They are rounded and have a small metal loop onto which you can attach the wire.
Better yet, wrap the wire one time around the object ( I use a rock ) and secure with a wrap of elec tape….
The reason is, if the thrown object get hung up in the tree ( which happens offen ) a good pull on the wire gets it out of the tape and the object will drop and wire retrieved.
best
Tom aa2vk
Thanks, Tom!
