Re: [amsat-bb] Noise, distortion and fading on AO-92 L/v downlink
To my ear, the L/v downlink just “sounds” more distorted and noisier than the U/v downlink. Perhaps something is coming in the L port or is internally generated. The downlink path in my radio is identical in L/v and U/v. The rapid fading last weekend was very noticeable at lower elevations and was close to a 30 sec period. At higher elevations, it was not noticeable. I’ll try to remember to screen capture the downlink waterfall next weekend. Ron W5RKN
I think part of it might be people off frequency a bit and generally weaker into the satellite.
Strong signals from well-equipped automatically Doppler corrected stations generally sound just fine, though there is sometimes radar noise that gets through.
73,
Paul, N8HM
On Mon, Dec 24, 2018 at 09:57 Ronald G. Parsons [email protected] wrote:
To my ear, the L/v downlink just “sounds” more distorted and noisier than the U/v downlink. Perhaps something is coming in the L port or is internally generated. The downlink path in my radio is identical in L/v and U/v. The rapid fading last weekend was very noticeable at lower elevations and was close to a 30 sec period. At higher elevations, it was not noticeable. I’ll try to remember to screen capture the downlink waterfall next weekend. Ron W5RKN
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Ron,
There was an exchange about this issue about same earlier this year.
My observation (from memory) and comments where as follows:
1) That the fading is on the L uplink, easy to tests: You just monitor the S/N with Foxtelem while listening to yourself on the downlink and you will notice that the fading occurs on your voice only. 2) The L-band is much more affected by the surrounding such as trees, building etc. than UHF or VHF. 3) Having too much power also does not help as if near a water plan or iron sheet roof nearby may create multi-path fading to the bird in spite of the distance. Keep the power low as in any case not much required (depending on the antenna gain).
Hope this help.
I wish all on the BB a Merry-Xmas and the best for 2019 (seems a promising one with the number of birds being sent up-there & Es’Hail 2, Hi!).
73
Jean Marc (3B8DU)
On Dec 24, 2018, at 6:55 PM, Ronald G. Parsons [email protected] wrote:
To my ear, the L/v downlink just “sounds” more distorted and noisier than the U/v downlink. Perhaps something is coming in the L port or is internally generated. The downlink path in my radio is identical in L/v and U/v. The rapid fading last weekend was very noticeable at lower elevations and was close to a 30 sec period. At higher elevations, it was not noticeable. I’ll try to remember to screen capture the downlink waterfall next weekend. Ron W5RKN
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
participants (3)
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Jean Marc Momple -
Paul Stoetzer -
Ronald G. Parsons