So right now I have purchased a Yaseu VX-6R, Telemini V3, Teledongle, Arrow Antenna 440-5 yagi and a patch cable. Am I going to need an attenuator? How important is an attenuator? Where do I buy one if needed or what kind? What else would you recommend? So far all I’ve done is configure Telemini through the Teledongle ground station via laptop for altimeter settings.
I’d like to learn to direction find a rocket. I’ve read the techniques posted by others but have zero experience at this HAM/rocketry RDFing. I was planing on plugging the handheld radio directly to the yagi tomorrow let me know if that’s a bad idea. Sorry for all the questions just kinda clueless in the just GPS it era.
Plugging it in and trying is *exactly* what you should do. I have very little experience with the Telemini, but I assume that, like the other telemetry enabled Telemetrum devices, that it does produce a periodic tone transmission for RDF. Play with this a lot, and I think you'll find it a satisfying (okay, sometimes frustrating) activity. 70cm transmissions are fairly susceptible to reflections, so keep that in mind when you're direction-finding around structures - and that can lead to some wild-goose chases, but be patient. This is better out in the country where we usually fly rockets, but even a grain bin or odd house can cause some confusion.
An attenuator will help the RDF process quite a bit, and the one that Kurt suggests is really handy. - its purpose is to diminish the signal strength reaching the receiver so that a change in antenna direction relative to the transmission will result in a significant change in the signal strength meter and audio signal. When you're distant from the transmitter, or it's signal is very small, you'll see and hear a significant change in signal strength as you move the antenna toward or away from the transmitter. As you get closer, you won't detect any change in signal strength as you change antenna direction. That's when you increase the attenuation, and get back to using the dynamic range of the s-meter on the display, and hear the audible change in signal quality as the antenna points toward vs. away from the transmitter. Make sense? Practice definitely helps - do it before it's time to find your rocket using this skill - you'll appreciate it.
*Do Not* wait until the rocket is on the ground to start your direction finding. Signal strength will be great when the rocket is in the air, but once on the ground, especially at a distance, the signal may suddenly be very small, so it's really important to head in the right general direction at first. (one big difference between this and GPS tracking)
You can employ some alternatives to an external active attenuator, with some sacrifices, but they're worth a try. The VX-6 (a great radio, by the way) does have a built-in attenuator that will help *some*, and as you get familiar with the radio, you'll learn how to turn that on and off, and also set the frequency step-size small enough to make little changes in tuning. The "active" or "offset" attenuator, like the K0OV device better isolates the radio from the transmission, as it's allowing you to tune off of the transmitted frequency, and get very close while still maintaining that dynamic range of signal strength meter and sound quality.
I've rambled enough, but happy to provide clarification, if you'd like. Foxhunting, or amateur radio direction finding has been a passion of mine, and believe it or not, it can get you a bunch closer to a rocket hidden in tall grass or crops than a GPS will do (though I love some of our GPS tracker options, too).
Do some Googling on amateur radio direction finding or RDF rocket tracking, and you'll find some good tutorials. Have fun.
[Edit: and now I see one of the other good, old, resurrected TRF threads on RDF tracking, so apologies for any repeated info:
https://www.rocketryforum.com/threads/grouchs-rdf-tips-and-techniques.127758/]
Mark
