Discussions > SkyRADAR General Discussions
Antenna Splitter
Mike F.:
Besides the 3dB loss, is there any reason I cannot use a single Comant XPDR/DME antenna and a high-quality 2-way splitter/combiner to feed both antenna inputs on the Skyradar D2? Even with the 3dB loss, I'm thinking an externally-mounted antenna would be better than the stock antennas inside the aircraft.
rdassow:
I'm not speaking on any authority other than I have background in RF theory.
I would say the splitter would be fine for the 978MHz spectrum but may be problematic in the new 1090MHz spectrum. I'm not sure how you could determine if this is actually the case when you test it since both frequency spectrums right now work similar BUT my understanding is that 978 is to be phased out over time. 978 will only be used in the rare case you don't have a groundstation and are interrogating airplane-to-airplane.
I could be wrong.
rdassow from techpilotz
SkyRADARSupport:
There is no reason you can not use splitter if you can live with 3db loss. It works fine with splitter and wideband antenna.
Regards!
--- Quote from: Mike F. on December 13, 2012, 06:26:31 AM ---Besides the 3dB loss, is there any reason I cannot use a single Comant XPDR/DME antenna and a high-quality 2-way splitter/combiner to feed both antenna inputs on the Skyradar D2? Even with the 3dB loss, I'm thinking an externally-mounted antenna would be better than the stock antennas inside the aircraft.
--- End quote ---
SkyRADARSupport:
I think you are mistaken about 978 MHz, it uses much better modulation and overall better designed for further expansion than 1090 MHz. It also carries weather and other information which is not available on 1090 MHz.
--- Quote from: rdassow on December 15, 2012, 04:40:10 PM ---I'm not speaking on any authority other than I have background in RF theory.
I would say the splitter would be fine for the 978MHz spectrum but may be problematic in the new 1090MHz spectrum. I'm not sure how you could determine if this is actually the case when you test it since both frequency spectrums right now work similar BUT my understanding is that 978 is to be phased out over time. 978 will only be used in the rare case you don't have a groundstation and are interrogating airplane-to-airplane.
I could be wrong.
rdassow from techpilotz
--- End quote ---
rdassow:
SkyRADARSupport,
I would love to know if you can verify this for certain as I am a ground instructor (U.S.A/FAA) and we're being told that 1090 is going to be 'the standard' for the US airspace system, and 978 is going to be 'the standard' outside the US airspace system.
Essentially I am being told: 1090 is how you are going to receive information from ground stations, such as displaying last minute TFR's, Nexrad, etc. 978 is going to be AIRCRAFT-TO-AIRCRAFT communication for traffic awareness outside the U.S. where ground station 1090 won't be available.
Please correct me if I am misunderstanding this, as the FSDO's don't seem to have a lot of answers.......
ryan from techpilotz
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