[aprssig] GPS 15H-W OEM Module

Larry McDavid lmcdavid at lmceng.com
Thu Sep 16 21:45:37 CDT 2004

Regarding the recent reflector questions about Garmin OEM GPS receivers:

I am using a Garmin 15H-W OEM GPS receiver in a mobile installation. 
This receiver has a MCX board-mounted connector for a remote GPS 
antenna; there is no on-board antenna.

The receiver is a single board, 1.8 x 1.4 x 0.33 inches with 
soldered-in-place shield cans over the entire board surfaces (both 
sides). The MCX receptacle connector protrudes slightly from one corner 
edge. There is a tiny, 8-circuit power/data connector along one edge also.

The 15H-W comes with a mating power/data connector, which is provided 
with eight individual, unjacketed wires about 8 inches long. You will 
need this cable assembly!

I had a lengthy discussion by email with a Garmin applications engineer 
about powering the remote GPS antenna. The 15H-W includes an excellent 
switching power supply allowing a wide range of input voltages; this 
supplies 3.3 vdc to the receiver and 3.3 vdc to the remote antenna.

So, what if your remote antenna expects 5 vdc? Well, there is a 
diode-protected input on the power/data cable for external antenna 
power. So, you just provide separate, regulated 5 vdc to one of those 8 
wires and this is directed to the MCX antenna connector; the internal 
diode isolates the receiver's 3.3 vdc power to the antenna.

Very early versions of this receiver required cutting a trace to remove 
the internal 3.3 vdc to the MCX connector; but, all current production 
(and for at least a year now) has included the isolation diode.

I had The RF Connection build for me a 6-inch long male, right-angle MCX 
to female bulkhead BNC cable assembly. I then mounted the 15H-W in a 
diecast zinc box with some power control circuitry.

I mounted a through-the-roof Larsen NMO active GPS antenna permanently 
on my station wagon roof. Very clean...

Keith - VE7GDH wrote:
> The Garmin GPS 15H / 15L does NOT have an antenna built in...

Best wishes,

Larry McDavid W6FUB
Anaheim, CA  (20 miles southeast of Los Angeles, near Disneyland)

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