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Re: More about QRM on AO-51 uplink



>On Thu, Feb 24, 2005 at 11:28:06PM +0100, Fabio Roccatagliata wrote:
>> Dear friends,
>>
>> I use the 910H and I always adjust the vfo using the 1khz step.
>> I think that should be a basic feature on the sat user "howto" and
>> probably it is.
>> The tone squelch decoder has probably many problems when trying to
>> decode subtones frequencies modified due the doppler effect and I
>> think that's should be the biggest doppler effect on and squelched FM

>
>Doppler effect shouldn't affect the tone frequency, given that it's
>FM modulation. Right?
>73
>Francesco       IZ5DWF


Francesco,
Even FM has doppler shift, It is just not as noticable as on SSB because
the descriminator (demodulator)
tracks the signal and converts the frequency/phase  modulation to
amplitude modulation. The Tone
frequency is so low, 250hz or less, that the amount of frequency shift
is on the order of millehertz. On
99.99% of the tone decoders this will make no difference.

73,
Keith N6ORS
----
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