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Author Topic:   Routing of GPS antenna coax...170 Montauk
Offset posted 06-08-2005 04:36 AM ET (US)   Profile for Offset   Send Email to Offset  
Any suggestions on running the coax cable from the antenna to the Garmin 178c sounder on a new 170 Montauk. Would like to mount on the top of the center railing in front of the windshield. Seem's to be no way to conceal the cable except for plastic ties. By the way I have to say again this boat is awesome.
bigjohn1 posted 06-08-2005 08:30 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
That's exactly where I mounted my GPS antenna and I had the same issue to deal with - a bundled up glob of extra cable. For now it is neatly wrapped up with zip ties tucked behind the chartplotter. When I get the motivation, I plan to cut the cable down to about 2' and splice the internal wires and wrap very securely with vulcanizing rubber tape - it'll remain just as waterproof as before the way I do it. I have read many sources which state to never cut transducer cable and some that recommend against cutting vhf coax cable - but none that say do not cut gps antenna cable. The trick is to solder the connections once you splice the shortened cable vice simply twisting the leads back together. On the subject of soldering itself, get a book on electrical soldering or read some online resources to learn how to do it right. Like so many things in life, "the devil is in the details" with regard to soldering electronics correctly. You cannot use the same shade tree techniques that will work adequately when soldering plumbing. Use vulcanizing tape on the splice instead of standard black electrical tape as it looks better (if done right), provides a better seal, and does not ooze all that gummy stuff when it gets hot like electrical tape does. In the end if I screw it up, all I'm out is a relatively cheap GPS antenna.
Offset posted 06-08-2005 01:07 PM ET (US)     Profile for Offset  Send Email to Offset     
Thanks Bigjohn. I've seen in Consumer Marine Electronics catalog what is called a Shakespeare Centerpin connector. Cut the cable then attatch and tighten.No soldering! Have you heard of anyone trying this connector?
SteveFC posted 06-08-2005 02:01 PM ET (US)     Profile for SteveFC  Send Email to SteveFC     
Seems to me that I read somewhere in the Garmin literature that you should not shorten the antenna cable. My Garmin 188c is dealer installed, with the dome antenna on top of the console, not the rail. The extra cable is bundled up and hanging out of the way inside the top of the console.

Marsh posted 06-08-2005 04:50 PM ET (US)     Profile for Marsh  Send Email to Marsh     
I have my GPS antenna placed similar to Steve...mine is in forward right corner of console top, up against the inside corner of the windshield. Completely out of the way. I have yet to lose a signal, but it's still new.


Offset posted 06-08-2005 06:52 PM ET (US)     Profile for Offset  Send Email to Offset     
I think I may go with that setup. Looks great with no mess.How was the antenna tightened down, also did they waterproof the opening??
Knot at Work posted 06-08-2005 07:31 PM ET (US)     Profile for Knot at Work  Send Email to Knot at Work     

my radio and my Garmin 188c is identically placed as yours. I love it.

Chuck Tribolet posted 06-08-2005 10:00 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I'll e-mailed Garmin about whether it was OK to shorten
the antenna cable on my 162. They said no functional problem,
but it would void the warantee on the antenna because it
was a modification. Since it was well off warantee, I cut.
I think maybe I have a little better signal strength through
the shorter cable. And I don't have a big coil of cable in
the console.

I just tie wrap the cable to the rail. I don't like the
idea of drilling holes in the rail because they would be
a stress riser.


bigjohn1 posted 06-09-2005 09:02 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
Offset, double check that article and ensure they are referencing a center pin connector for a gps antenna and not a vhf antenna. I did try the gold crimp-on Shakespear center pin connector for my vhf and it worked superbly. To my knowledge, there is no available crimp-on center pin connector for a gps antenna. I would think it would need to be brand-specific since so many gps manufacturers utilize proprietary connectors on their specific gps antenna cable....anyone know anything to the contrary?
Chuck Tribolet posted 06-09-2005 03:44 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
My Garmin 162 uses a standard BNC connector for the antenna,
and there was a crimp on CenterPin (brand name) for that
coax size. No sweat, no solder, works fine.

The pictures in the 178C manual make it look like it has a
BNC connector also.


bsmotril posted 06-09-2005 05:45 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
The signal loss per length of cable is much greater for GPS signals which are in the 1 Gigahertz range than they are for VHF which is 160 Mhz. Everything in the signal path becomes a factor at those high frequencies, and the quality of the cable and connector are critical to the weak GPS signal reaching the unit. I would avoid anything but a soldered connection for a GPS and make sure it also has a very good moisture seal of the connector cable junction to keep moisture out of the cable jacket. For VHF, it is not so critical, but I'd still solder everything for long term reliability. The signal levels of GPS are very tiny compared to VHF, and every little bit of loss you can eliminate is to your benefit. BillS
bigjohn1 posted 06-09-2005 09:28 PM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
Chuck, I stand corrected and did not realize there was a universal standard for these connectors (in your case BNC). I will research this with my NAVMAN unit and see if it utilizes same.
jimh posted 06-09-2005 11:39 PM ET (US)     Profile for jimh  Send Email to jimh     
I would bet the farm that GPS receivers with remote antennas use down convertors in the antenna. There is no way 1 GHz signals can travel on the tiny, high loss coax used with these devices.
Chuck Tribolet posted 06-09-2005 11:53 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Other Garmins use other connectors than BNC. My old 175 used
some little connector that I think was called TN. The
3010/3006 (dream on, Chuck) use a serial port connection
with several wires, the whole GPS receiver is in the "Antenna". I don't offhand know what the connector is.
The unit on top of the console is just a display.

Essentially all GPS antennas are amplified. DC goes up the
cable to power the amplifier, amplified signal comes back


SteveFC posted 06-10-2005 08:27 AM ET (US)     Profile for SteveFC  Send Email to SteveFC     
I crawled under the boat cover last night to get a picture of my console interior and feed the local mosquitoes.

Note that the full length antenna wire is neatly bundled up and tucked behind the battery. This installation was done by my dealer. I'm clueless myself, but my dealer's people have a reputation for doing things right. And yes, they waterproofed both openings.

MosslandingJoe posted 06-10-2005 10:56 AM ET (US)     Profile for MosslandingJoe  Send Email to MosslandingJoe     
I have a Raymarine C-80, it was installed by Johnson and Hicks in Santa Cruz. The way they routed the GPS cable was to drill two small holes in the railing,one at the counsel and one at the top of the railing at the sensor position,using the railing as a raceway. I don't see how this weakened the railing, and it made for a very neat installation. When I need to grab the railing, thats all I grab.The penetrations into the railing were positively sealed, and only a very small amount of cable is exposed,very sli
jimh posted 06-10-2005 10:16 PM ET (US)     Profile for jimh  Send Email to jimh     
Steve--Nice pictures. Thanks for the captions and the callouts.
bluewaterpirate posted 06-11-2005 01:33 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
I don't have a Nantucket but I'd thought you could get another look at a different installation. My previous Whaler was an 18 Dauntless so I faced some of the same issues u have with ur Nantuckets. I flush mounted my GPS antenna on that boat (as I have done with the Ventura). As u'll c I flush mounted my Ray RC435 GPS & ICOM 502 VHF & gimble mounted my Ray GS500 FF. I used a terminal block as a NMEA output/input pass thru medium.

My 210 Ventura has:

Small enclosure for electronic with an angled instrumemt panel infront.
Easy access to behind my electronics.

So this how I did the installation. I coiled the long cable runs from both the GPS/VHF/Cell Phone antennas.[

Hope this helped ......


bluewaterpirate posted 06-11-2005 01:50 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Sorry about the 1st picture (bad link).

Here it is again ......


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