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Radio Direction Finding
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PA3BNX:
19-12-2014
21-12-2014

Subject Corner-reflector antenna
---------------------------------

I want to easy transform the 4x doppler antenna array
to a amplitude direction finder (Watson Watt)

By adding just a crossed screen in centre of the 4
antenna array it would become 4 corner reflector antenna

If I made that of cardboard with hinges with ALU foil glued on it
it just can place or remove it
 
Than I have to switch the RX from FM to AM
and I am done !
I think the 4 corner antenna have higher gain
and is more suited for pulse detection then doppler
detection.

(When manually used with a switch box that can
switch each antenna separate on you could use this also for DF chasing
with just a receiver with s - meter and no need for a yagi turn-able
on roof of car)

I think it catches a lot of air pressure in a driving car but could be
used when not driving or stationary application.

Place a screen between the 4 monopoles or dipoles
from a standard SuperSimpleSoundDoppler antenna array
to transform it to a Am direction finder with correlation detector
and more gain and better pulse detection
Receiver mode changed from FM to  AM

Curved reflector increases the gain (But more difficult to construct)

Some expected performance details
------------------------------------
F/B value 20 - 35 dB ?
Gain maximal 7 dB with 1/2 lambda driven element


angle usually 90 degrees

S = distance corner to radiator
w = width about 2x lambda radiator
T = screen length one site 1/2 lambda more then S


Feed point impedance versus distance to corner

Do not
With a distance S = 0.5 lambda gives 2 main directions


Bigger distance then 0.65 to .85 lambda okay about 5 dB gain


Any one with more info let me now !!


SeanB:
You probably could use a simple GRP cylinder to enclose the 4 reflectors and elements to make an antenna that would be more aerodynamic, though of course using a higher frequency would make it smaller as well, but then limit your range considerably.

You probably could use 2 frequencies, with a lower one giving the range and the higher one for localising. You could make it more difficult using a different repetition rate on the 2 transmitters though, with the localiser chirping more often, but the lower repetition rate of the high frequency one ensuring you have more difficulty in locating the fox. you could even separate the 2 transmitters, and have a 2 part hunt by having the second one a preset distance known beforehand ( within a rough area) from the localising transmitter.
PA3BNX:
Hello Every Body,

I did made a prototype for AM VHF/UHF RDF with 4060 and tl072 (No voltage regulator needed)

And a picture of the cross screen placed between a standard pseudo doppler antenna array.

EA4FRD:
Dear All,

I keep trying to build a ARDF system for T-hunting (by car) in 27MHz (CB). I built sometime ago a system based on magnetic antennas (90 cm separation on the roof), IC switcher and PA3BNX software but not to much sucess.

I should keep working in that but maybe you guys know any other better system for CB. I shown the PA3BNX for HF suggested with loops, but I would need more information about plans and distances.

Thanks sincerely in advance.

Carlos.
PA3BNX:
Hello EveryBody,

I send to pictures for  direction find loops.

See also pictures on this site.  11 meter loop
http://verbed.home.xs4all.nl/hamspace/pe5edw/11m_peilantenne/11m_peilantenne.htm

You Tube Sokol dl1roj


Ahha doppler demo KD6IRE AI6RE
... detailpage

73's
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