[aprssig] Reccomend GPS for Kenwood TM-D710

Stephen H. Smith wa8lmf2 at aol.com
Fri Mar 28 20:10:05 EDT 2008

Chuck Gooden wrote:
> I would suggest a Garmin GPS 18 LVC.  I bought mine on ebay for $34.00
> Joseph M. Durnal wrote:
>> What is a good GPS to interface with a Kenwood TM-D710?  I really
>> don't need anything fancy with screens or directions or anything, just
>> a reliable GPS.  I suppose I would prefer an external antenna for the
>> GPS and something fairly low cost.
>> 73 de Joseph Durnal NE3R
>> _______________________________________________
>> aprssig mailing list
>> aprssig at lists.tapr.org
>> https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig

WARNING!!   With a GPS18 LVC you must provide a 5 volt power source.  
*DO NOT* connect this unit directly to a source above 5 VDC (such as the 
car's 12 VDC system), or you will let all the magic smoke out.   The 
GPS18 PC is the same unit with a 12 vDC-to-5VDC cigarette lighter 
adapter included. 

All-in-one combination receiver-and-patch-antenna units like the GPS 18 
or the low cost units sold by Byonics

     < http://www.byonics.com/tinytrak/gps.php >

or Argent Data at:

     < https://www.argentdata.com/catalog/index.php?cPath=23 >

are no larger than external antennas only, and far less hassle than 
dealing with separate antennnas.   Due to the horrendous coax loss at 
1.6 GHz where GPS operates, especially with the small RG-174-sized cable 
commonly used, external antennas must be amplified (i.e. active) to 
offset the loss.  

This means:

a) you must supply power to the external antenna (usually through the 

b) With 15 dB or more gain and no significant frequency selectivity, 
they are prone to  being overloaded and blocked by nearby 19 GHz PCS 
cell site or 1.2GHz ham operations a.

c) You have to deal with installing nasty sub-miniature microwave RF 
connectors on tiny coax. .  

The all-in-one units have the antenna connected directly to the receiver 
with no cable loss at all.  You just supply DC power in and serial data 
comes out. The antennas are passive (non-amplified) and much less prone 
to overload in urban areas.   Any of the modern all-in-one mouse-type 
faceless units (a.k.a. "hockey puck units) have excellent sensitivity 
and will work well just resting on the front of the dash at the bottom 
of the windshield.  If you do want to mount them externally, they have 
magnets in them that will stick to the roof of the car.


Stephen H. Smith    wa8lmf (at) aol.com
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