[VHFcontesting] Use of APRS in the Rover

[Ev Tupis]

----- Original Message ----
From: Dan Evans <dan.evans at insightbb.com>


So how bad do you think the APRS signal is going to be for the 2m SSB 
station?
---------------------------

The frequency difference between 144.39 and 144.2 is only 190-kHz.  This is much too narrow for a filter of any sort.  There are two general strategies to employ for APRS use in a rover:

On the SSB side, use a transverter for SSB operation -- one with a high dynamic range front.  I use the SSB Electronics transverter on 2-meters, and the band is quiet within 5-kHz of a KW station only 8km from my home (when they are active).

On the APRS side, use low power (really! 300mW may be ok), poor antenna (really!) and separate the antenna from the SSB antenna by as great of a distance as possible.  Remember, all you need to do is be heard by a digipeater and you'll be repeated for others to hear.  You'll already be on a hilltop or knoll, so probably LOS to a digipeater.  Alternately, consider powering-on the APRS system only when the QSO rate is low, or while in-transit and not on SSB, etc.

As with so many other things, there are many variations of these strategies that can be made to work, but this can give folks a few ideas to digest.

Regards,
Ev, W2EV

PS: The advice for APRS is *opposite* that of HamIM, where high power and good antennas are the norm.  Why the difference?  HamIM takes place on 147.585 (over 3-MHz away!), and is simplex in nature.  A 70-watt 1/2 second TX is barely noticed on the 2m SSB transceiver.





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