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[aprssig] Low band APRS (was Re: 9600b UHF APRS IS THE FUTURE OFAPRS)

Ben Jackson ben at ben.com
Tue Oct 10 19:53:22 UTC 2006


On Tue, Oct 10, 2006 at 01:59:05PM -0400, Robert Bruninga wrote:
> 
> I used to think that as well, but I finally got a 10m rig and
> put it in the car and then put a beaocn on the roof at work into
> a 5/8 wave vertical on a metal roof.  I was absolutely
> astonished when I drove home that the range was LESS than 2
> meters!

I was working on a simple 30m beacon (see some earlier messages on this
list) and when it worked the range was great, but the band only opened
up for me a few times a day, at least at 5 watts.  It also required a
good antenna.

What I wanted to do with it was up the power a bit and make use it in
an ocean buoy, but given the reduced efficiency I was going to get from
a short vertical, and the relative lack of 30m gates, I figured it would
not be very effective.

> But if anyone can prove me wrong here, I woiuld love to find a
> way to use the 10m band.  But NOT FM.  There are not enough FM
> channels on the 10m band to be able to afford one for APRS,

One thing that quickly became clear on 30m was that 200Hz SSB tone spacing
requires a very precise oscillator.  For unattended APRS operation at
30m you're talking 1 or 2ppm accuracy.  At 10m you'd have to do even
better.  It almost requires a GPS source that provides some kind of time
discipline you can use with the transmitter.

-- 
Ben Jackson AD7GD
<ben at ben.com>
http://www.ben.com/




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