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Author Topic:   gps installation 17ft montauk
whaler al posted 12-05-2000 04:55 PM ET (US)   Profile for whaler al   Send Email to whaler al  
Can i mount dgps antena on the same side of the console as my vhf.
jimh posted 12-05-2000 10:29 PM ET (US)     Profile for jimh  Send Email to jimh     
The DGPS antenna (as distinct from the GPS antenna) is intended to receive signals from the MF band, approximately 300 KHz.

As such, the antenna will be very inefficient because its aperture (inches) is extremely small in terms of the wavelength (hundreds of feet) of the signal being received, and therefore it is likely that the antenna will either be an "active-antenna"
(by which I mean the antenna element itself contains built-in electronic amplification) or the antenna will feed a very high-gain amplifier at the receiver.

In either case, locating the DGPS antenna near your VHF antenna may expose it to strong RF fields when you are transmitting.

I would carefully review the recommendations of the manufacturer of the DGPS antenna/receiver regarding the minimum distance it should be located away from transmitting antennas.


jimh posted 12-05-2000 10:37 PM ET (US)     Profile for jimh  Send Email to jimh     
Also, I wanted to mention that the location of the DGPS beacon receiver antenna does not affect the computed position.

The GPS receiver resolves its position based on where its antenna is physically located, but the signals from the DGPS beacon just contain offsets or error corrections, and the antenna that receives them could be hundreds of feet away from the GPS antenna.


triblet posted 12-06-2000 11:46 AM ET (US)     Profile for triblet  Send Email to triblet     
In practice, DGPS antennas have an ampilfier
built into the base. If it's a whip, the
antenna will have it's own ground and you
need to make sure that gets to a good earth
(not electrical, they aren' necessarily the
same) ground or it won't work well. If it's
an H-field mushroom, gounding isn't
as important.

Neither will work well inside your garage.

You will spend very little time transmitting
on the VHF. If you miss a DGPS packet or
two while gabbing on the two-way, it's not
a problem.

What DGPS did you get?

Chuck Tribolet

whaler al posted 12-06-2000 05:39 PM ET (US)     Profile for whaler al  Send Email to whaler al     
dear jihm
thank you for your expert advice.
whaler al posted 12-06-2000 05:50 PM ET (US)     Profile for whaler al  Send Email to whaler al     
dear tribolet
thank you for your input I have the FURUNO DGPS 35. I had this on my 26ft stamas and it worked great the only thing is that it was mounted on the hard top. mounting it on my montauk is a little complicated.
any more input from you or jihm would be good

whaler al
triblet posted 12-06-2000 06:58 PM ET (US)     Profile for triblet  Send Email to triblet     
As I remember the Furuno 3x series has a
combinded GPS/DGPS antenna. I'd mount it
the same way I have my GPS and DPGS antennas
(separate) mounted: on the console rail using
a stainless rail mount (West Marine p/n
548404) Use a tiewrap every three or four
inches to secure the cable to the rail.

Chuck Tribolet

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