VHF antenna distance from GPS antenna/reciever - The Hull Truth

rcouret · 04-21-2004, 04:04 PM

After doing a search I see where some recommend that the vhf antenna be at least 3' from
gps antenna. In dealing with my situation (21'cc with 3' whip antenna)and as noticed on many similar center console there is
not always a good position or distance to locate and maintain a 3' spacing. Idealy for me I would like to mount the gps antenna on top the console rail to the right and have the 3' vhf whip about 8" behind it mounted to the top of console. I'm I looking for problems?

Parthery · 04-21-2004, 04:13 PM

My GPS and VHF antennas are mounted about 6" apart on the side of my W/A.* I can fold one forward and one backward to get them out of the way.

The VHF antenna was there before the GPS antenna went on.* Absolutely no difference in my VHF reception and the GPS locks on within about 15 seconds of being powered up.

I would say put them on the rail and don't worry about them.

Mumblerone · 04-21-2004, 06:04 PM

I don't see a problem with your installation.* Why are you using a 3'*whip antenna for the VHF?* Why not at least a Digital 4' (preferably 8') mounted on the side of console?* www.digitalantenna.com.* The ss whips I've seen are for emergency use only.* I'd put a good antenna on.* www.consumersmarine.com sells Digital.*

rcouret · 04-22-2004, 12:57 PM

Mumblerone, the majority of my fishing is inland marsh and lakes.
At best, on rare occasions, maybe 5-6 mile off shore. Always boats within sight.
Radio mainly for emergency. 3' with handle my situation/distance. The reason for my antenna
locations is that the top of my console was designed as a platform for sight casting. With having a taller
antenna or placing them on opposite side's of the console would either limit the small casting area,
get in the way of casting, or in the case of the gps antenna (on top of rail) obstruct my view/navigation
when under way. Hence the best layout...put both on one side, that being the opposite side as the helm.
thanks,rcouret

Gil Morgan · 04-22-2004, 03:06 PM

You would not have a problem under normal VHF receive mode. In transmit mode, there is a possibility that the VHF transmit signal could flood the front end of the GPS and you may momentarily loose the GPS signals. Why don't you hold the VHF antenna close to the GPS antenna, hit the XMIT button on the VHF and see what happens.

Sea_Dad · 04-22-2004, 10:21 PM

the gps runs on Ghz, the vhf runs on Mhz. The vhf will not affect the gps antenna.

The 3 feet is in reference to the vhf unit itself. Most radios state to have at least that much distance so you dont create feedback in the vhf itself, not interference with the gps.

colliwh · 04-25-2004, 08:21 PM

I've had the same experience with my antennas........they are closer than any 3' and I have seen no problems at all.

rcouret · 04-25-2004, 09:21 PM

Well I installed the vhf antenna and I'm waiting on the rail mount for the gps antenna which is on
backorder and will not be in for 2-3 weeks. When installed and tested I will post the results.
Should be 8-12" apart. Thanks, Bob

Biff123 · 08-11-2004, 11:08 AM

Quote:

Sea_Dad - 4/22/2004 9:21 PM

The gps runs on Ghz, the vhf runs on Mhz. The vhf will not affect the gps antenna.
The 3 feet is in reference to the vhf unit itself. Most radios state to have at least that much distance so you dont create feedback in the vhf itself, not interference with the gps.

Now I'm confused... What needs to be seperated from what? The GPS Ant. from the VHF unit?

I am in the process of installing a Garmin 2006C with its external antenna, and a Standard Horizon Quest VHF and its antenna. That makes 4 pieces of equipment, that I am trying to all cram onto my console (no Ttop). Now which pieces exactly need to be separated? Thanks -

radioshop · 08-11-2004, 11:52 AM

Biff,
Why cram the GPS antenna onto the console? You can put the GPS antenna practically anywhere. The best place on your Mako would be on front deck, but clear of any bow railings.

If you could stick the VHF antenna on the gunwale you'd like it's performance a whole lot more. Not to mention, you're radiating 25 watts, I tend to like some seperation.

dwh_1987 · 08-11-2004, 12:00 PM

Biff, I think SeaDad is talking about a requirement for the VHF cable to be at least 3 feet long.*

In general, you're better off if you can keep your VHF antenna cable and FF transducer cable separated from other stuff, but I haven't seen very many small boats where you can really pull that off.* Make sure you don't wind*either antenna cable up into*a tight coil trying to gain clearance.* You'll lose more than you gain in performance.**Try to get as much clearance between the two systems as you reasonably can, but don't kill yourself.* *

The biggest thing to be careful about with the Garmin is the very fine gauge wires that run from the GPS antenna.* They need to be installed with some strain relief, as any tension on the wire coming out of a crimp or whatever will cause it to break.* This superfine wire is my only real complaint about the Garmin.*

Frank007 · 08-11-2004, 01:37 PM

No, he is talking about the need to have the VHF antenna at least 3 feet from the VHF radio. When they are closer, you sometimes get feedback in the VHF (electronic noise/squealing). It is not a problem in many installations. I have heard that it is less likely to be a problem with ICOM radios because they are better shielded than many other brands. If you want to mount the VHF antenna closer than 3 feet to the VHF radio, try a temporary mounting to ensure you don't have a feedback problem.

This has nothing to do with how close either of the VHF components are to the GPS unit or its antenna.