VHF Radio woes

[CAPTCURTIS]

Has anyone had this problem? Have a 61 ft Blackwell. My 2 vhf radios will both trans great , but if other boats are more than about 8 miles away , I cannot hear them. I have changed both radios from Icom to Standard ... changed both antennae and the problem still exist. Doesn't matter if engins {Man-1300hp} are running or not . We tried a portable radio , portable antennae and a portable power supply...and it would not work on my bridge either...I have had 6 Marine electronics companies from Manteo , NC to Ft Pierce ,Fl look at them ,but none of the 6 have fixed them...My transmitions are great and boats 35-50 miles can hear me , I just cannot hear back...Anyone have any ideas ????? I have even disconnected all batteries , removed epirbs and laptops and connected radio to a portable 12 volt battery ... I still cannot hear .......???????

[Big Bertha]

Hard to think of anything to solve that problem, particularly since you have already had qualified personel look at your system from Electronics Mechanics. The only times I have had any problems transmitting out was once due to the ground needing to be connected on my ICOM and another time I needed a special base plate at the bottom of an all fibreglas antenna to bounce the signal. Sometimes event the most qualified can miss something; hope whatever your problem is, in the end, is a simple one.:confused:

[CAPTCURTIS]

thanks for the comeback... i can transmitt great ... i get asked to relay all the time just cannot hear more than about 8-10 miles...

[New zealand fisher]

Hi are you working the repeater channel or line of sight?

[Capt Rick]

I don't know much about radios,,but are your outrigger's grounded?

Could this be a ground problem with something on the boat not going to ground,,like the radio??? Ill bet ya its a simple fix..............

[HaveNone]

Distance is = to the square root of 1.42x antenna height.

A boat with a 12’ antenna has a range of 4.2 miles.

Curvature of the earth and all the physics stuff

[Capt Rick]

,,,,I hate to be the one to tell you this HaveNone,,,,but your math is a little off.
It will be 30 miles (and sometimes more) on a very bad day on a boat his size. The tip of his antenna must be about 30 feet from the surface of the water.
A small 5 watt hand held will transmit 5 miles on a good day.

He is having "receiving" problems,,,not transmitting problems. Something is blocking him from getting the signal from other boats.

[HaveNone]

http://www.naval.com/sight/index.htm

Here is a link for a vhf line of site calculator for those not good in math.

[Capt Rick]

This might help you,,,,,,

http://www.catfleet21.org/rigging/June.htm

Here is more info.

http://www.biminicruisingguide.com/pdfs/page-172-175-vhf-radio.pdf

[HaveNone]

The second link Capt Rick posted is a good example of line of sight communications.
Using the calculator on my post.

Antenna height 1: 100 ground station
Antenna height 2: 12 boat
Range should be around 19 miles

Antenna height 1: 12 boat
Antenna height 2: 12 boat
Range should be around 10 miles

Antenna height 1: 12 boat
Antenna height 2: 6 boat
Range should be around 8 miles


Math was off in the first calculation

[Capt Rick]

Last spring I did a rescue in the Broad river Beaufort, SC. I called the coast guard in Charleston,SC.
Thats about 50 miles away.............................................. ...........