The AM Forum

After the latest windex storm event last week I lashed up a fast Windom to get 80, 40, 20 and 10 back quickly. Used the good ol' VS1AA , 1937 variant.  Fine on 80 and 40, but super reactive and very high SWR on 20.  Steve, 'KX, did the strange wind get any of your SE Va wires too? Heard it was pretty severe over your way.

So research continues. This guy has some really neat design thoughts. I'm keeping in mind that the British 80/75 band stops at 3800 though.

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=15686 (http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=15686)

Anyone have experience with it or similar Windoms?

The trick with a real Windom is to us current sensors (bulbs, etc) to find the sweet spot for attaching the single feeder. Some good text on this in some of the old HBs and/or QSTs.

No wind here today, but was some nearby. Wind last week took down a branch that busted my 10 meter loop and smashed my 10 meter Yagi. Sheesh!

Yeah, I thought about your 40 meter two element wires when seeing the news reports about that last blow.  You had a nice write up and pix about all the wires on your spread.

Here's the modern equiv. of light bulb tuning. Somewhere in his pages he mentions the old days with bulbs.
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=15686 (http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=15686)

I dunno, seems like a lot of work compared to 102 ft dipole fed with ladder line. Using a tuner anyway. But I'm going to soldier on since it's already up and will be fun to see if I can trim a little a get decent results with matching.  Not looking for low SWr's as much as just getting it in range of the tuner, which it isn't now on 20.

The 7 th 1/2 wave of 24.9xx MHz harmonic reference with even and odd harmonics pretty well nails the relationship. 80m is considered odd. The whole thread is worth reading. 

Latest data. Relative settings on LC matching network, not actual L or C.

L is a rotary inductor about 35 uh max; rotary dial reads 0 to 25, hi H.
C is 350 pf / 2KV or so;  dial reads 0 to 10, max C.

There is a -jX to +jX crossover in the middle of 80.
Ran out of compensating C for a couple of freqs. Probably humps up possibly to infinity where C, flat values show.

Still measuring and possibly modifying away.
Fun.

The Windom antenna is now working pretty well on several bands.
LOA                132 ft. , 40.225 m.  (20.117 m. each side of center line.)
Long side,    91.05 ft. , 27.751 m.
Short side,   40.93 ft. , 12.474 m.   (7.64 m. from center line.)
Feed line,     56.93 ft. , 17.35 m.

1.) Impedances at several freqs. given in first pix showing MMANA calcs.

SWR's are based on 200 ohms since that is seems to be the popular feed impedance in a lot of the literature with 1:4 baluns usually being dropped in at that point.  I find the vertical, open wire of a true Windom works well and allows some vertical polarization to help with low take-off angles that a coax feed may not. 

Note that most bands are loadable with an "L" network lo to hi Z tuner;
30 meters is horrible. The rest I've tuned ok with my L-net.  The attached files are of course are MMANA models and assume perfectly straight runs as shown. My antenna feed line takes off from the horizontal top at less that 90 deg. angle, runs a ways then downward to basement window feed point on the back of the shelf mounted L-net.

Note also in the calcs that no extra distance from ground is entered since the Z axis runs the full 57 ft.  Guess what?  My antenna isn't 57 ft. high, more like 35, but the wire is there.  More deviation from the model but fun anyway. The real one at least finally loaded up with dimensions given.

Also in every band, a fairly high current node or low voltage node was shown at the tuner's output.  Little RF in the shack with dimensions found.

2.) Far field shown on 40 and 20 in next two pix.  80, of course was a big ball, mostly radiating at high angles. 

 

Even though the higher freqs. loaded up ok, I don't expect a lot. Lobes were surprisingly broad but with very little low angle radiation.

Pix 1 is 21.2Mhz and 2 is 29.5Mhz, a real sky warmer and moon illuminator.

And Check out pix 3,  3D on 14.2Mhz for kicks. Hain't to shabby.

As mentioned in a nearby thread, Windoms are wild in just about element's and feed line dimension.  Everything affects it; ground field/plane/soil, height above ground, frequency, ...you name it.

I Don't believe commercial Windoms or OCF's magically work on all bands with SWR's advertised in most cases.  Some trimming will need to be done and that trimming will affect everything else.  A lot of fun I guess.