Mobile Radio Direction Finding with a TDOA device

[@MyronDYoder]

Thanks for the video! I had a similar box like this that was a kit by Ramsey Electronics and it worked well. This is the first I have seen of a commercially available unit. Questions: 1. What frequencies will this work on? 2. Does it have to be FM? 3. And when using it in the mobile, is the spacing between the antennas critical? And 4. Is the antenna coax length of each antenna important?

[@RDFfun]

Frequency range: Most amateur RDF is performed around 140MHz. This could be used at 440MHz, but there are more reflections at those (and higher) frequencies. Antenna size and spacing will be a complicating factor as you get very far away from 140 to 440 MHz. FM: Yes, I believe for this to work correctly you need to be using an FM RECEIVER - however, I have used an FM receiver with this to RDF AM (Aircraft) frequencies, it does work for RDF, but is more difficult to understand the audio. The spacing between the two antennas in the array is not critical, but usually recommended to be somewhere from 1/8 to less than 1/2 wavelength. The coax length from each antenna to the RDF box should be the same, and the same type of coax. Coax length from the receiver to the RDF box is not critical.

[@Mike-y7f2n]

Will this work for 121.5 and a 406 mhz? Elt signal?

[@RDFfun]

I have used it to DF aircraft/airport transmissions on VHF. It works, but may not be the best answer. Your receiver will need to be able to monitor aircraft transmissions (that are transmitted in AM mode) but instead monitor them in FM mode. You may have difficulty finding a radio that will do this. (My Yaesu FT-60 will).