VHF Question

[Max Simmons]

Recently while boating with three other vessels, we ran into some problems transmitting with our VHF.* When transmitting, two of the other boats could barely hear us.* This was when we were all in sight of each other.* The third boat heard us loud and clear.* We could hear all of them just fine.* We experimneted a little bit, but with no change.* We have experienced the same thing recently while hailing marinas.* Port of Friday Harbor told us our signal was faint while we were only a couple hundered yards off shore.* Other marinas hear us loud and clear.*

The unit is a Standard Horizon Eclipse

Any idea where to start with this one?

Thanks *

 

[Marin]

If you are transmitting on high power the signal can sometimes "skip" over nearby receivers. Ideally boaters should normally transmit on low power to keep their signal from interfering with other transmissions farther away and just use high power when actually trying to broadcast over longer distances. In practice I suspect most boaters leave their radios on high power all the time (we do). So if you've been leaving your radio on high power all the time and you experience problems with nearby receivers hearing you, switch to low power and see if that improves things.

If it doesn't then it could be a whole host of things. For example if you have multiple VHF radios and antennas and if the antennas are mounted a multiple of 17" from each other, I've been told by the electronics shop we use that this can create interference between the antennas that can affect transmissions or reception or both.

 

[Capn Chuck]

Max, Here is a good discussion on VHF antennas and might be a good starting point for you. As you can see even the orientation of the antenna matters.
http://www.boat-project.com/tutorials/vhfant.htm
Chuck

 

[ralphyost]

You report a repeat of the problem with other radio receivers of your transmission.

I suspect you have an installation irregularity. You can immediately tell if your anteanna is mounted properly and vertical. If it is vertical, which I assume so, then I would check your antenna wire and connections. Have a trained electronics person check your VSWR (Voltage Standing Wave Ratio).
A poor VSWR will reduced your ERP (effective radiated power).

You also need to remember that not every VHF radio receiver is equal. Some are better than others at picking up low signals. Personally, I have found that ICOM radios have very high quality receivers which combine both low signal reception capability with good noise rejection. (Having good performance of both of those is difficult to achieve in radio design.)
R.

 

[ralphyost]

Capn Chuck wrote:

Max, Here is a good discussion on VHF antennas and might be a good starting point for you. As you can see even the orientation of the antenna matters.
http://www.boat-project.com/tutorials/vhfant.htm
Chuck

Chuck

That is a great reference site !!

R.

*

 

[C lectric]

Chuck,
I agree with Ralph - GOOD SITE>
Thank you