Simply Half-Wave Trapped Antennas Addendum 1 - Nice to Have Stuff

Paul Carlson in a small part of his lab

This is a short rant about [electronic] tools and what you should anticipate arming yourself with.

If you are new to ham radio and foresee getting into serious tinkering, First get yourself a DMM (Digital Multimeter).

Period.

These range from literally free (with a coupon from Harbor Freight Tools) to a Fluke (or higher grade instrument) that will cost you almost a thousand buckos. Scout YouTube for some reviews but cease once your eyes begin to glass over. Guys like Dave, the histrionic Aussie host of the EEVBLOG series, will have you believing you cannot survive without owning a Fluke meter that can withstand being thrown off a skyscraper. M. J. Lortin, the laconic Englishman, will have you sound asleep five minutes into part one of an hour long video of which there are two additional parts.

Other guys will show you anywhere from three to ten DMMs they bought just so they can do a review of the infinitesimally subtle differences between each. Trust me, if you get a decent one for about $15-50 with auto-ranging and a few other features you might want, you will be fine. Also, trust me: it will not be the last one you own.

O.K., that covers DMMs and we'll leave oscilloscopes for later. But, when you get one, you will be surprised how you did without it.

I would only add -- for the moment -- that you make a modest investment into three items that will save you a lot of headaches, guesswork, and make this corner of antenna and radio building a lot of fun. These are a component checker, an LC meter, and an antenna analyzer. Examples of these are shown below but are not exact product recommendations. They are part of the bounty of cheap Chinese stuff exported and sold on eBay for a reasonable price. Recommendations can be sought amongst friends and on VHF/UHF technical nets and round tables. Wise shopping will set you back from $20-100 tops.

Component checkers are surprisingly good at telling you a lot about each little doodad you hoover up at swap meets from transistors to inductors and including resistors, capacitors, diodes, and other stuff. They might even be good enough to tell you about the inductors and capacitors you are using for your traps. They are around $15-25 on eBay.

LC meters are higher quality gadgets that give you a more accurate reading of the inductors and capacitors. If your component checker is crappy, then consider one of these. They are a little more than $20 on eBay.

Antenna analyzers range from cheap to literally a kilobuck (or more). If you pick up one for HF only (1-60 MHz), expect to pay around $50-80 for a low end one. I have a couple I picked up in that price range and am perfectly content with what they show me and don't need curves of graphs drawn.

But, trust me, you start tinkering and you will always see "something better" and end up having about three or four items that essentially do the same thing. Of late, there is a "NanoVNA" on eBay that sells for about $60 and will actually draw curves of your "network" (the trap). If it is sexy enough to compel you to open your wallet, knock yourself out.

If you want to go old school, you might consider picking up something called a Grid Dip Meter or "GDO" (Grid Dip Oscillator). Back in the day (the 1950s onward), these were considered the "Swiss Army Knife" of test instruments as they could be used to test LC tank circuits, antenna resonance, and even serve as a signal generator. Here, Alan Wolke, W2AEW, does a nice video on how these can be used.

When my dad passed away back in 1992, I inherited his Millen 90651A which, at the time, was considered the Cadillac of GDOs. I developed a "jones" for these and over the course of time owned a number. The collection dwindled but I kept my dad's and the cream of the crop and still use them quite a bit, to wit:

The Heathkit transistorized version of this -- like the one in Alan's video -- is worthwhile and is as near as good as the Millen. The Millens and the Heathkits are not worth owning if they are in questionable condition or do not have the coils with them. Most of the time, the ones offered on eBay are dog meat and way overpriced at that. Occasionally, one will come along and is worth nabbing. Even better is picking up one at a swap meet or ham fest.

Alan produces some outstanding technical videos and they are well worth watching. His work is thorough, explanations are straightforward, and he publishes those magnificent notes he makes for download from a link on each video.

Another simple "old-school" tool is the noise bridge. These are simple circuits that generate white noise. As explained by an Australian, Ralph Klimek in a 1995 article on his website:

A noise bridge is an impedance measuring device that can measure real and imaginary components of complex impedance at RF frequencies. It uses a radio receiver as a detection device and a broadband noise source as the excitation source for the bridge. This eliminates the need for a precision signal generator notwithstanding the fact that the average signal generator does not have sufficient output amplitude to excite and bridge and simple detector. A radio receiver is an excellent detector being sensitive down to microvolt signals and low bandwidth. The noise bridge is an excellent antenna tuning instrument because it gives a rapid and precision measurement and also the noise power induced into the antenna is very small and will not cause interference to others.

Basically, is is an even cheaper version of an antenna analyzer and, if mastered, can be quite useful.
There are "commercial" products available like the venerable Palomar Engineers version or an old Heathkit, and an MFJ unit that turn up from time to time on eBay priced from around $20 on up. I would not, however, pay more than $40 for one. These are shown below:

There is a kit available from QRPGuys for about $20 plus shipping. It works identically to the units above but the advantage is that you get the experience of building it and there is a comprehensive assembly manual here and an "operations manual" here.

Like the GDO above, if you see a noise bridge at a swap meet or ham fest for a reasonable price, pick it up and learn to use it. Anyone can drive one of those idiot-proof antenna analyzers but it takes going old-school to really understand the underlying electronics and antenna theory.

By the way, Paul Carlson is one of the more impressive techs on YouTube. His lab (a smidge of which is shown in the picture above) is truly expansive and, given that he is prone to radios and equipment built in the 50s and 60s, borders on the Gothic. Don't let this put you off. The man is a genius -- both in the literal sense and as a statement of my admiration for him. His YouTube channel is a treasure trove. Here is the intro.