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RSSI as lost plane finder

PostPosted: Thu May 24, 2012 4:13 pm
by BillGriffiths100
I was flying at the Club field today surrounded by oilseed rape, which is horrible and impenetrable, a flyer lost his plane in the field and we had a hard time finding it, because the crop makes it impossible to see or move around.
I am using Frsky telemetry which gives RSSI signal strength, it occurred to me before flying I would see if I could locate my plane (in the pits) by putting the transmitter in low power range test mode and looking at the RSSI signal.
Yes it worked and it gave a very directional homing in signal (with the aerial horizontal).
So everyone with RSSI can use this trick to find lost planes in crops and woods.

Re: RSSI as lost plane finder

PostPosted: Fri May 25, 2012 2:29 am
by pldb64
Bill,

Are you suggesting to have the aerial horizontal to the ground or aerial at right angles to the root of the aerial? (or both). I'm assuming you mean both as (with my limited understanding of RF) if you point the aerial directly at the model, you should be seeing a degraded return signal strength.

So for this to work most effectively, you'd get the strongest RSSI if you point the root of the aerial directly at the model but with the aerial at right angles to the root and horizontal to the ground? Have i got that right?

Secondarily, i recall that with some/all of the FrSky Rx's, they are supposed to make some sort of beeping noise if the Tx is turned off (ie signal lost). I vaguely recall someone saying that they'd used this to find their model as well. Can anyone confirm/deny this? Mine doesn't seem to do this so i wondered if it was some failsafe setup step that i'd missed

Cheers
Peter

Re: RSSI as lost plane finder

PostPosted: Sat May 26, 2012 10:10 am
by BillGriffiths100
So for this to work most effectively, you'd get the strongest RSSI if you point the root of the aerial directly at the model but with the aerial at right angles to the root and horizontal to the ground? Have i got that right?


Yes that seemed to give the best directional indication, it worked with the aerial straight up but not as well, experiment for yourself you'll see what I mean.
There is an RSSI alarm that's set at a certain level of signal loss that's kind of irrelevant but on mine it seems to be set at 45% and does beep.
The RX's do not seem to beep just sulk I don't think there's a sounder in mine
A much better manual for the FLD-02 is found here:
http://www.rcgroups.com/forums/showatt. ... 1337333645
and gives details for setting the alarm levels on the voltages and the RSSI, print a copy it gives information the original "manual" does not!
You'd never guess how to set the voltage alarms in 100 years!

Re: RSSI as lost plane finder

PostPosted: Wed Jul 18, 2012 1:56 pm
by dwentz
It even works better if you attach a small wifi yagi or cantenna to the transmitter. The higher gain antenna is much more directional. The cantenna is very narrow and shielded from all sides.

Dale