Radio advice - Not transmitting?

[Richard_Peevor]

Hello - I wonder if anyone out there can offer me any suggestions. I have recently installed a new VHF onto my boat. It previously worked without difficulty on a RIB. I connected it to the aerial that was already on my mast and I can receive but not transmit. I changed the aerial and this didnt help.

When transmitting and the button is held down there is radio silence from my end and also the transmitting LED works but no marina/coastguard can hear.. any suggestions as what may be wrong?

Any help much appreciated..

Richard Peevor

rpeevor@hotmail.com
07980 595887

 

[alex_rogers]

Someone posted a similar problem a while back and it turned out to be a bad power connection - receiving takes very little current but transmitting on full power should draw 2-3 amps and thus requires a decent connection. Otherwise it sounds like a problem with the radio if swapping antenna didn't help.

Alex Rogers
<A target="_blank" HREF=http://www.YachtsAtSea.com> www.YachtsAtSea.com </A>

 

[jimi]

When you hold down the tranmit button you won't hear anything, this is because most VHF's either transmit or receive but do'nt do both at the same time. Have you tried attaching it to the emergency aerial and see if it works with that?

 

[byron]

Check the power supply is A.1. In receive mode they need little power. On transmit you are 'pulling' plenty. A good sturdy power supply is essential.

http://www.alexander-advertising.co.uk

 

[chriscallender]

If the radio was working fine before then its highly unlikely that is now broken (although if it has tried to trasmit and the antenna was not connected properly its possible that has damaged the power amplifier).

Like other readers have posted, if we assume the radio is OK that leaves the power supply or antenna both of which are likely culprits. You could also try transmitting to a very close receiver (eg handheld) to see if anything is being transmitted at all. Remember to use a ship to ship channel if you do this so that transmit and receive are on the same frequency.

Try measuring how much current it takes in transmit. Also try both settings of the 1w/25w switch. Unfortunately its just a case of trying things until something works

Chris

 

[Guest]

Disconnect the aerial lead. Put your fingers across the aerial lead socket and transmit at 25 watts. If all is well you will not be able to hold your fingers on due to the heat. Don't keep transmitting.

 

[ericw]

Hi Richard !

As a radio ham, the only advice I 'd offer besides what's already been posted is to check that the coaxial connectors are all ok and that there is a good connection at both ends of the coax cable i.e at the transmitter end and up at the antenna.
U can still receive signals with almost any connection (even sticking the end of your finger over the coax input on some frequencies !!), but for tx mode the connection needs to be perfect otherwise the radio energy generated won't be able to escape and will only damage the tx final amplifier stage of the radio.
As somebody mentioned, it's probably worth trying out an emergency antenna - if u get a transmit signal from the radio with this, then u know it's the coax connection up to the boat antenna that's the problem - if no transmit signal, then sounds like the tx amp. is blown - shouldn't be too expensive to replace.

Hope u get it sorted !

Regards ... Eric.

www.HarryHindsight.com

 

[Guest]

Sounds like the RF output amp has failed. You need a VSWR meter in the circuit between the antenna and the TXVR. A high VSWR will tell you that its an Antenna problem and low or no forward power will mean the RF Amp is defective.
If you can not borrow a meter from a friendly source they are available at most ham outlets for around £15 for a cheapo. If the loan unit is available also ask to borrow a 50ohm dummy load, as this then will isolate the Antenna.
RF Amps are not very robust when it comes to impedance mismatch (no antenna load) so please be careful with the testing!
Good luck
Neil

 

[Bergman]

Good advice.

But

If you don't have access to a VSWR meter then connect a 20-30 watt bulb across the antenna socket. If it fails to light a bit then no output. If it does light don't leave on TX for very long but go down faulty antenna route.

Another test if you have gear is to measure DC current drwn by radio - should increase by about 2 amp when you go onto TX.

If PA is bust (most likely guess) then probably worth considering new wireless.

 

[snowleopard]

did you change the antenna cable?

common problem is moisture getting into the outer braid of the coax. transmission will then be reduced to a fraction of normal power. low voltage is also a problem though more applicable to handhelds