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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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