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[aprssig] Nuvi 350 - GTRANS - D7 not beaconing

Stephen H. Smith wa8lmf2 at aol.com
Fri Jun 15 16:40:31 UTC 2012


On 6/15/2012 11:10 AM, Robert Kirk wrote:
> My mobile gps rig, Nuvi 350 to  GTRANS to Kenwood D7 is only transmitting 
> intemittently; sometimes fixed by resetting radio, sometimes not. Anyone else 
> have this problem? Both GPS & radio seem to work fine independently. Time to 
> give up & upgrade?
>
> Bob, N3OZB
>

Are you referring to a TH-D7?    Are you using an antenna directly on the 
radio?   If so, almost certainly you are experiencing  RFI issues from lack of 
a decent ground/counterpoise for the attached whip.    Try an external antenna 
with a decent ground; i.e. a mag mount on the roof of a vehicle or something 
similar.

When you grip a handheld in your hand for voice operation, your body (basically 
a bag of 80% salt water and fairly conductive) becomes a reasonable ground for 
the radio.  When you let the radio sit by itself as an APRS tracker: a) You 
lose the grounding effect and b) you have a bunch of external wiring attached 
to the radio.

The body of a TH-D7 (or any hand-held at two meters) is simply NOT LARGE 
ENOUGH, by itself, to be a decent ground for a two-meter whip.  (The chassis 
of  the radio would have to have a height of around 19-20" to be an effective 
ground/counterpoise for a whip on two meters.)     As a result, any attached 
wiring will become part of the antenna system, and will be crawling with RF 
that gets into the connected hardware,  that will cause random lockups, 
feedback, CPU crashes,etc.   (Unless you take extreme RFI suppression measures 
such as RF chokes, ferrite cores, etc  on the cables coming out of the radio.)

-------------------------------------------------------------------------------

--

Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
Home Page:          http://wa8lmf.net


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