VHF Signal Strength Question

[Max Simmons]

Recently out boating with 3 other boats.* When contacting each other via VHF, two of the three complained that my signal came in very weak, one heard us just fine.* We were able to hear all 3 that same and they were all able to contact each other without any problem.* All 3 have newer equipent, no older than 3 years.* My setup is the oldest, maybe 12 years old or so.* Time for new antenna?

 

[Capn Chuck]

Hard to say. Could be antenna, could be connectors, could be radio.
Only way to be sure is to put a meter like this http://tinyurl.com/dcta6f on the unit and test it. Chuck

-- Edited by Capn Chuck on Tuesday 14th of April 2009 04:32:27 PM

 

[Penta]

Could be as simple as your microphone is defective and not giving you the voice level that it should.
You do not say if the other vessels were hearing you clear but weak ; bad microphone most likely or if your signal was weak and noisy ; bad transmission from radio or antenna system.
If your transmissions were clear but weak try and find another microphone, from the same radio, and test your system with it - quick and easy test before you go tearing into things.

John Tones MV Penta
Sidney, BC

 

[Capn Chuck]

Penta wrote:

Could be as simple as your microphone is defective and not giving you the voice level that it should.
You do not say if the other vessels were hearing you clear but weak ; bad microphone most likely or if your signal was weak and noisy ; bad transmission from radio or antenna system.
If your transmissions were clear but weak try and find another microphone, from the same radio, and test your system with it - quick and easy test before you go tearing into things.

John Tones MV Penta
Sidney, BC

That is a good test but odds are that a 12 year old VHF will have the mike hardwired in to the set so borrowing one will mean taking two sets apart, then rewiring them. A test meter will determine the problem and put you on the right path. Chuck

*

 

[Chris Foster]

My $0.02:

Two most likely scenarios:

- bad antenna and/or coax.* This has the potential to make your signal directional - good radiation in some directions, poor in others.* Simplest way to test is to see if another boat gets similar signal quality as you turn the boat through 360 degrees.*

If you have 12 year old coax, that would be the first thing to replace.* In particular, any sort of crimping, kinking, or connector problems can give all sorts of trouble.* If you even think about replacing the antenna or radio, you*shouldUse a *replace the coax, too - so do it first; that may be all it is.* Use a good quality coax - RG142 or RG400, not RG58.** Use crimped connectors with the proper crimper.* Examples:

Cable:* http://www.chiefaircraft.com/airsec/Aircraft/InstallationSupply/Wire.html#Coax
Crimper:* http://www.chiefaircraft.com/airsec/Aircraft/Tools/TerminalCrimper.html

- transmitter off frequency.* Different receivers have different capabilities to capture an off-frequency signal, so the same transmission might be quite reasonable for one radio and almost undecipherable to another.* A decent radio shop should be able to do a quick bench test to verify transmit frequency and output power.

My suggestion would be to do the radio bench test and replace the coax.* If the radio tests out OK and you still have the problem, then replace the antenna.

 

[Marin]

Don't know if this is relevant, but on our small boat, a 17' Arima, the VHF transmitted just fine on the low wattage setting but not on 25 watts. Figured we needed a new radio but the owner of the marine electronics shop we use said that before we buy a new radio, check all the power connections to the radio. if there is a corroded connector, bad switch in the line, etc., this could be keeping the radio from getting enough power to transmit at 25 watts. Sure enough, a selector switch I had put in the power line when I installed the radio was corroded. Bypassed the switch temporarily and the radio was back to transmitting just fine on 25 watts.* So you might want to first check the power feed to to the radio to make sure the wires are okay, connectors are clean and tight, etc.


-- Edited by Marin on Wednesday 15th of April 2009 12:40:49 AM