Thursday, May 31, 2012


For my own reference as much as yours, a little more detail on the balun I'm using with my new Windom antenna. The starting point was this web page.

The PVC pipe on hand here was 1-5/8" in diameter, so I dropped a turn (or a little less -- just over 11 turns for each of the two wires), figuring if it didn't work, I'd start over. It's also only got one color of wire, as I have a nice big spool of sky-blue insulated #14, purchased awhile back for antenna experiments. I scribbled on the ends of one winding with a black marker. You don't even really have to do that, since the bifilar windings are flat: the wire that starts on top, ends on top. Here's the completed balun: And a close-up of the connections at the coax end: The top end is just 6-32 nuts and bolts (mostly brass) and solder lugs.

Here it is all wrapped up in self-amalgamating tape: It didn't change the tuning, so I guess it must be okay stuff at 7 mc/s.

Refinements: use fatter brass hardware for the antenna connections. Use polystyrene drain tubing, sold as "styrene" for the coil form: it has better properties than PVC at HF. Mount the coax connection facing down! And you could do like the pros and encapsulate the whole thing in PVC pipe. (I have one somewhere around here, a slightly more sophisticated trifilar job, coated with epoxy. It had held up well, last time I saw it. --If I could only remember where!)

Tuesday, May 29, 2012


The G5RV -- more of a "bent extended double Zepp," which I think Varney would have disavowed -- I use doesn't load up well on 40 meters. It's been arranged to fit the available space and it's just not that good a match.

I don't worry much -- if you can get some energy into your antenna, it'll work even with lousy SWR -- but it was pretty bad.

So I put up an off-center-fed 40 m dipole, a sort of a coax-fed Windom.* With the feedpoint at the 80%/20% point, it should look close to 200 Ohms and take a 4:1 transformer to present a decent match to 50 Ohms.

The antenna part is easy enough -- take 67' of wire and divide accordingly, then make it fit (I ended up having to bend both ends).

The transformer... It was a holiday. The ham store we haven't got was closed. But all you really need is wire and a coil form (PVC pipe) and a little hardware: (The branch is not really that close to it.) Ended up with 11 bifilar turns of #14 house wire on approximately 1- 1/2" diameter PVC. Hams get all worked up over these but with about three bucks of materials in it, this version is not too painful to have to redo from scratch if the first try doesn't work. My design is all rule-of-thumb and fudge-factored from other versions on the Web.

Here's a funny angle on the transformer and one of the bends: It's about 20' up at the highest points.

Finished it after dark -- I'd installed a coax feedthrough but had to put the connectors on the coax -- and had a QSO within minutes of getting on the air. (Real DX: Warsaw, IN) And it tunes up on 40 meters just fine!
* Loren G. Windom, W8GZ, yet another of the antenna-designing hams from Columbus, OH. You may have heard of the other one -- W8JK, John Krause, of the 8JK HF beam and the helical antenna (both modes!).

Saturday, May 19, 2012


Part of one row of the outside area -- less than a tenth of the total. There's no place to get a really good overview photograph but take it from me, the Hamvention is huge!

One commercial vendor offered miniature straight keys, J-38ish (the general Bunnell "Triumph" pattern, widely used in the U.S.) but about 3/8 full size. I wanted one...but didn't buy one on sight and, of course, could not find them again.

But that was all I missed at Dayton. I didn't buy anything large, but several smaller items came home with me along with plenty of photographs. Above, the Morse Telegraph Club, with a bit of the Vibroplex booth in the background. (I bought a couple of "Vari-Speed" attachments from Vibroplex, a nice pre-WW II invention the company brought back several years ago. The new owner and staff were there, with the full line of keys.)

Begali! Peitro Begali is at the right, perhaps the best key designer alive (apologies to Mike Marsh, who does beautiful work) and certainly the most prolific; he demonstrated his Swedish-style straight key and let me give it a try. That blurry photo was the best I could get. The Begali booth is solidly busy all the time and a clear photo is all but impossible.

Speaking of keys, that's the ballcap and one ear of Mr. Enigma (the WW II encryption device) and Mr. Keys himself, Professor Tom Perera, W1TP, and above him, a huge and very wondrous strange key, with two sets of contacts and adjustments galore.

More keys. Readers of this blog will recognize the bugs, and perhaps the unusual Western Electric straight key at the top center, but how about the gadgets over at the right? They're "registers," with clockwork pulling a paper tape under a stylus that "writes" the incoming code as long or short lines. This technology preceded transcribing code by sound; it never occurred to Morse or Vail that anyone could manage that....until operators started doing it. The machines shown are roughly Civil War vintage.
Here's a beauty! A Collins 20V3 AM broadcast transmitter, 1 kW with cutback to as low as 250 Watts. Once a stalwart of local "coffeepot" AMs, most surviving examples are either relegated to backup transmitter service or, like this one, have been converted to ham use. You can see two of the tubes glowing at the left; there's another pair at the right: 2 RF finals, 2 modulators. Originally, 2 or 4 mercury-vapor rectifiers would have been glowing a happy purple-blue at the bottom of the window. This rig was up on the bed of a small truck but it's odds-on the 866s have been replaced by solid-state diodes; most people don't enjoy the failure mode of M-V rectifiers, or the half-hour-plus warm-up time if you don't keep them cooking all the time. This rig offers a surprise for the unwary: there's 110 VDC on the RF output! It operates a relay that shuts the transmitter off if there's an arc, and will give you quite a jolt if you don't know about it. (BT, DT.)

Another, even bigger transmitter, though I think it was a kiloWatt job, too. Originally it was a nice sober Gates gray. I was unable to capture the full glory of this repaint, complete with a yellow "tube guy," lightning bolts and floating eyeballs. Why? Why not! (Anything that keeps this old iron around and on the air is okay with me. Perhaps that's barbaric, but they are going to landfills in droves.)

Not every transmitter requires its own truck. This is a "1929 type" high-C rig probably built in the 1980s. It's a directly-coupled high-power oscillator. ("High power" being some tens of Watts, with luck.) Some hams run these on the air -- properly set up, they work fine, despite a tendency to "yoop" mildly as the antenna sways in the breeze.

Receivers! (One of those things is not like the others, and I don't mean the "doghouse" power supply for the HRO-7, second from left. Can you ID the odd box out?)Hallicrafters, in fair shape.
National, a WW II set, ditto.
RCA, I think. In rough shape; you can't see the clock-type tuning scale, with "hour" and "minute" hand for reading down to the kilocycle. Or so.

RME 69, with the hard-to-find preselector. I wanted to buy this one; it's in decent shape, unrestored, and the price was right. But it would need weeks of work and I am full up for projects. Note the absence of labels for the controls -- designer E. G. Shalkhauser, W9CI, was of the opinion anyone who would be operating the receiver should either be smart enough to figure them out or sufficiently interested to read the manual. RME made some of the best receivers of their day; after WW II, they built a few more models and were bought up by Electro-Voice. E-V eventually sold the name but it is tempting to wonder if some of the "DNA" remained: long after RME was gone, some retired E-V engineers started up a little ham radio company called Ten-Tec. They've done all right.

This came home with me. Made right here in Indy, the EZ-TOON aftermarket vernier tuning knob! A 1920s aftermarket accessory for receivers. Found two of them. Here's the user's side.

Among my purchases: a couple of books from the RSGB, the previously-mentioned Varispeeds (and a contact burnisher: I nearly lost a QSO two days ago thanks to dirty key contacts!), a pair of 6BG6 tubes, a kind of an octal 807 beam power tube, some round "Ohmite" type knobs, an NOS Hammarlund plug-in coil form in the original box, ceramic standoff insulators and a National variable condenser.

And that's a glimpse of my day at the Hamvention. I'm thinking about driving back Sunday -- need to top up the oil in my car, first.