[amsat-bb] Re: [ao51-modes] Re: AO-51 now requires 67 Hz PL tone; activity reports appreciated

Andrew Glasbrenner glasbrenner at mindspring.com
Thu Apr 21 06:32:45 PDT 2011

-----Original Message-----
>From: "Eric Knaps, ON4HF" <on4hf at telenet.be>
>Just worked  AO-51 without 67Hz tone. I noticed that the carrier drops 
>out sometimes. I guess you activate the carrier again with subtone but 
>i'm not sure.

Thanks Eric. You are correct. In this newer PL scheme, the 67 Hz tone turns the transmitter on for two minutes, and the uplink receiver is open squelched. If someone else on the satellite has their tone on and activates the repeater, you can have a QSO with them in the 2 minute window. The open squelch also prevents the logjam effect we see on the older PL mode, where multiple stations may be transmitting simultaneously with none getting through, and maybe not realizing why.

73, Drew KO4MA
AMSAT-NA VP Operations

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