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
As a general principle what is considered a reasonable tolerance for CTCSS (e.g. on repeaters)? As the next frequency up from 67Hz is 69.3Hz +/-2Hz sounds very risky. I know not all transceivers support the 69.3Hz tone, jumping straight from 67Hz to 71.9Hz instead but I believe that this is the exception rather than the rule (even my older handhelds all support 69.3Hz).
A quick Google search for "PL Tone" yielded this definition on one repeater site ...
"The system is designed around a set of relatively low frequency tones (32 or 38 depending on which "standard" you use) ranging from 67.0 Hz to 250.3 Hz. The tones are a perfect sine wave and the frequency tolerance is very tight, typically +/- 0.5 Hz. The tone is encoded and injected into the transmitter after the audio shaping circuits. The frequency deviation (level) is typically 0.4 to 0.8 kHz which is rather insignificant when compared to the typical 5 kHz voice deviation."
73 de
Félim M3HIM IO91ot Aylesbury, Buckinghamshire, UK ----- Original Message ----- From: "Bill Ress" bill@hsmicrowave.com To: amsat-bb@amsat.org 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 AMSAT-BB@amsat.org. 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
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" bill@hsmicrowave.com To: amsat-bb@amsat.org 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 AMSAT-BB@amsat.org. 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
participants (3)
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Bill Ress -
Francesco Messineo -
Félim Doyle M3HIM