[amsat-bb] AO 91 Rumbling Noise
wa4sca at gmail.com
Mon Jan 22 21:08:42 UTC 2018
You are hearing the Data Under Voice telemetry. It is transmitted in the 0-200 Hz range where CTCSS tones are normally sent. Whether you hear it, and how much, depends on how sharply your rig cuts off the low frequencies. All the Fox spacecraft, except for the unlaunched Fox-1E, use it so as to provide telemetry while allowing repeater operations.
<From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Bernie
<Sent: Monday, January 22, 2018 14:44 PM
<To: amsat-bb at amsat.org
<Subject: [amsat-bb] AO 91 Rumbling Noise
<Forgive me if someone has already discussed this, but I noticed a
<"rumbling" noise in the background during this morning's AO 91 pass.
<What is that? It almost sounds like a train is passing by. It was not
<dependent on someone transmitting as it was present even while there was
<no one speaking. But, it faded away as soon as the pass was over at my QTH.
<73 de Bernie, KF0QS
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