[aprssig] EB-432/PCSAT2/APRS Question

[hasan schiers]

Hi Keith,

Yep, early in the pass, tune the rx high (that's why I set 5 khz high when 
unattended).

I was addressing the receive portion only, because he indicated he wasn't 
decoding many packets. Of course, with a 2m uplink, you might find that 
uplink doppler correction isn't needed for the vast majority of the pass. As 
I recall the doppler at 2m is 1/3 that of 70cm (linear relationship to 
frequency). In any case, I was only replying to the rx side, which on 70cm 
requires doppler correction, or to get the largest number of available 
packets, some judicious planning to minimize the doppler issue.

The easiest way to do this is to offset rx a bit on the high side of center, 
and gather most of your packets from lower passes (glancing across the front 
of your antenna instead of coming right at you). It has worked well for me, 
but ymmv based on vegetation and obstruction losses which can be quite 
significant at 70cm.

73,

...hasan, N0AN
----- Original Message ----- 
From: "VE7GDH" <ve7gdh at rac.ca>
To: <aprssig at lists.tapr.org>
Sent: Friday, May 26, 2006 10:38 AM
Subject: Re: [aprssig] EB-432/PCSAT2/APRS Question


> Hasan N0AN wrote...
>
>> I do not do doppler correction, so I deliberately set the vfo 5 khz
>> high to catch the early part of a pass. If you set it dead center,
>> that is the fastest point of relative motion for an overhead pass,
>> and the signal won't be in the passband very long. If you choose a lower
>> pass  the doppler rate is lower, so if you pick the freq judiciously, you
>> can maximize the number of possible packets in the passband, BUT you have
>> to set the VFO freq higher due to doppler (in the early part of a pass).
>
> Just curious... when the "bird" is whizzing towards you, wouldn't you want
> your receive frequency high and your transmit frequency low? For 
> approaching
> satellites, would you do a bit better if you adjusted both instead of just
> enhancing your receive?
>
> 73 es cul - Keith VE7GDH
> --
> "I may be lost, but I know exactly where I am!"
>
>
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