Thanks for the replies, guys. That explains it. I'd just never heard it before on other FM birds.
73 de Bernie, KF0QS
On 1/22/2018 2:08 PM, Alan wrote:
Bernie,
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.
73,
Alan WA4SCA
<-----Original Message----- <From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bernie <and Cheryl <Sent: Monday, January 22, 2018 14:44 PM <To: [email protected] <Subject: [amsat-bb] AO 91 Rumbling Noise < <Dear Folks: < <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 < <_______________________________________________ <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