[IRCA] Antenna success, mostly...

[Tim Hills <thills@xxxxxxxxxxxxx>]

I've been working on a remote controlled ferrite antenna that has at 
least some unidirectional characteristics.

My latest attempt is in the attic over the garage and is working better 
than I expected so far. I had to rush it a bit since I start a job that 
will require a lot of travel and hours on 12/01 and probably won't have 
time to play with it again until late April.

The "rod" is a composite, 1 8" rod of about 400 permeability and a 5" 
rod of ~125 permeability in line with a 1" gap between them surrounded 
by 6 6" rods ~125 Perm. All rods are 3/8" diameter and overall length is 
14". 28t CT 100/44 Litz for the tuned winding and a 12t 40/44 pickup 
winding. Rotator (and 2 of the 6" rods) were salvaged from a dead 
Ray-Jefferson ADF.

Varactor tuning and a preamp using low noise/high IMD immunity dual gate 
MOSFETS. Balanced RF to the receiver is fed through dual RG-6 that was 
hooked to the sat. dish with dual grounding block attached to a Copper 
drain pipe that runs under most of the basement. Balun on the receiver 
side matches it to the unbalanced 75Ohm input of the DX-440. Cheap IR 
surveillance camera mounted to the roof joist is my directional indicator.

The end with the 8" rod has a much deeper null than the the other. WNAX 
(5KW@54 miles) gets completely nulled on one side but still shows 5 bars 
on the 440 on the other. Locals at 1140 and 1320 still come through very 
strong even with power to the antenna shut off, the 440 has lousy 
shielding but the 6' between grounding block and balun is probably 
enough to pick them up. No noticeable intermod even with the strong 
locals and adjacent chan rejection is excellent, still some slop around 
1140 and 1320 but that could be partly the poor shielding on the 
receiver but I can tune out IBOC on the lower part of the band..

I left the regen/Q multiplier out for now and it doesn't have the 
ability to tilt. Both would improve the performance of the antenna but 
for now I'm just going to put an EM shield on it and call it good. Busy 
winter/spring and slack summer/fall for work so by the next fall DX 
opening I should be pretty well set up.

I'll see if I can find my vidcap card and post a demo to youtube showing 
the directional capability of this antenna. It's come a long way from 
the earlier version Rick got to play with.

Tim Hills
Sioux Falls, SD
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