Hello all,
I don't know the answer about the tolerance of AO-51's tone decoder, but if the purpose is to make a tone encoder I can tell how I designed and built two working encoders for all PL (38 if I remember correctly) tones. My problem was total lack of test instruments at that time, so I had to use a no tune approach. The only thing I could think of was to make a "poor man's" dds with a microcontroller and an R/2R 8 bit DAC followed by a low pass active filter. The only frequency reference is the microcontroller external crystal oscillator. The only tuning I needed was on the output level and I just used a multi-turn trimmer and moving it to the point that the tone squelch on a TH-D7 receiver opened. The first unit built is an external one for the TR-9130 vhf radio (it's a little box with an lcd display and two buttons to chose tone frequency). I use it for AO-51 and SO-50. I've never had problems getting into those two sats. The second unit I built is for the TR-851 and it's internal, using the little space of the original kenwood board. I just had to reverse engineer the signals that the radio generated for the original board (I've never seen one). This second unit has only been tested with the TH-D7, since I don't think we have a working satellite with FM tone squelched uplink on the 70 cm band. Hope it helps.
73 de IS0FKQ
----- Original Message ----- From: "Bill Ress" [email protected] To: [email protected] Sent: Tuesday, August 22, 2006 7:59 PM Subject: [amsat-bb] 67 Hz PL Frequency Tolerance?
I've looked through the AMSAT web site and the AO-51 book but can't any information about the frequency tolerance of the satellite receive system to the 67 Hz PL tone.
I believe someone way back when actually did some measurements after it was launched but I can't find it either. Does +/- 2 Hz sound right? What about the level (deviation) require? Is it the same for the Mode V and L receivers?
Regards and thanks...Bill - N6GHz _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb