-----Original Message-----

From: "Eric Knaps, ON4HF" on4hf@telenet.be

Hello,

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. 73, Eric.

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