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General Discussion / Re: Transceiver Interference
« on: February 03, 2016, 09:02:52 am »
The first few pages, before it drifts off into marketing spiel, is one of the best SDR receiver primers I've ever seen. Thanks Paul!
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Transponders transmit on 1090Mhz but receive on 1030Mhz so can't see any blow up caused by that.Yes, you're right of course, although 60MHz separation at 1GHz is not a lot for the front end filtering to work on. I have a feeling that if our ADS-B in dongles had their antennas mounted on the underside of the aircraft in the line of fire from the transponder antenna then they would be less than happy!
I'm afraid dedicated ADS-B out is only any use if you don't have any sort of transponder.That's actually not quite correct. Most CAT and quite a lot of high end GA carries more than one transponder for redundancy, however only one can be in use at a time. One reason for this is that the transmitter of transponder 1 would blow up the receiver of transponder 2 and vice-versa, since they are operating on exactly the same frequency. Another issue is having two transponders both squawking the same aircraft ID, squawk code, etc. from the same position. Jolly confusing to radars and their controllers!
CAA/NATS will not permit more than one 1090Mhz transmission device in an aircraft.
Transponders are really hungry, as well as expensive.Modern Mode S transponders aren't particularly greedy. Typical average power consumption is well under 1A at 12V which is easily within the capabilities of a small battery to provide for a few hours of flight. A non-squawking ADS-B out transmitter would require much the same power budget.
the FLARM dipole is 145mm, I thought the best length for PAW was 164mm?It depends what velocity factor (VF) you use. VF varies, amongst other things, with the aspect ratio of the antenna - thickness of elements vs. length, the conductor material/plating and the type of insulation, if any.
Any other suggestions on approach gratefully received.It sounds like you're covering all the bases there Steve. I'm the Senior Air Traffic Engineer at Carlisle Airport and as such have various useful contacts in CAA SARG. Generally when I engage with them on GA issues they are very happy to put me in contact with the relevant key personnel. For example I've been doing quite a lot of work on the 8.33kHz saga. If you think this might provide you with another route in to CAA or if I can help with your workload then I am happy to assist.
The NEMA GGA message in particular defines if the position fix is:I did some tests today with the GPS/GLONASS USB Dongle outside with a clear view of the southern sky and found that it does see EGNOS and it sets the DGPS flag accordingly:
0 Fix not available or invalid
1 GPS SPS Mode, fix valid
2 Differential GPS, SPS Mode, fix valid
3 GPS PPS Mode, fix valid
I've analysed the outputs from a Garmin 196 and the GPS/GLONOS UBS device used on the PilotAware.
GPS/GLONASS USB Dongle
$GPGGA,113156.00,5126.31393,N,00103.39777,W,1,08,1.01,59.2,M,46.7,M,,*78