VHF signal

Xk59D · 10 January 2013, 16:41

just going through the yearly todo list (why is it always so long :-)

last season while doing my normal pre sail coastgaurd check they said they were struggling to hear me. i can hear them no probs. i confirmed it was not location based as i sailed to outside the station and done same thing with same results on a diff day.

i assume i have a problem in the system somewhere but not sure where to start, open to ways to proceed here?

remembering i can receive ok i'm not sure?

cheers

GJ0KYZ · 10 January 2013, 18:35

Check you radio isn't set to low output power.

Copinsay · 10 January 2013, 19:04

Do check if different with the engine running or not... sometimes the noise of the engine via the microphone, or electrical interference via the wiring can cause that, and so be fine when the engine has stopped. Good to try with a mate or your backup radio (?) ... and of course only transmit when on the water :o)

willk · 10 January 2013, 19:36

All of those. Also - was the mic very wet? I've seen that knock out comms mysteriously...

wurble wurble wurble

simon23 · 10 January 2013, 20:10

I had that,it was a bad conection on the aeriel,easy fix!

Johnscubanut · 10 January 2013, 21:49

Agree, go for the connections first. Solder em!

Xk59D · 10 January 2013, 23:23

thanks for the suggestions folks, will go through them in due course and see how i fair.

i can rule out water in mic or it is set to low power. so i assume that leaves the coax/connectors or the antenna.

cheers

willk · 10 January 2013, 23:40

I had an odd one once - the power supply to the radio was poor (blackened copper) and when I tried to transmit - the set would drop into low TX and then pop back to Hi afterwards. It took me quite some time to spot it and work out what was wrong. Might be worth a peek...

Copinsay · 11 January 2013, 00:12

Do you recall if the CG said they could not hear you because of low signal strength (transmit issues?) OR poor readability (ie strong signal but audio problems) as that will give you some very useful clues too. Or else try do that check with someone to determine.

So "assume that leaves coax/connectors or the antenna" would most likely not be the defect if strong signal but poor readability was the symptom.

Steve (ex-comms engineer)

Xk59D · 11 January 2013, 14:55

steve, the CG never mentioned any of that unfortunately. i can get a handheld and comm with the boat and check for myself though if it will assist.

cheers

Copinsay · 11 January 2013, 17:14

Sounds good to me (excuse the pun!)

Boatintercoms · 11 January 2013, 18:44

I had this fault reported on some lifeboats I've worked on, and it's aways been water in the coax cable, but it's a good idea to change the antenna while your at it, Procom antennas are pretty good.

Ian M · 11 January 2013, 19:26

Quote:

Originally Posted by Xk59D

last season while doing my normal pre sail coastgaurd check they said they were struggling to hear me. i can hear them no probs. i confirmed it was not location based as i sailed to outside the station and done same thing with same results on a diff day.

Sounds simple to me, you just need to speak up

Ian (current comms engineer

)

City Radio · 28 January 2013, 23:00

Any marine radio is useless without a decent tuned antenna and good quality coaxial cable. The power transmitted only works through an efficient antenna.
1. Ensure all power and antenna connections are in good order.
2. Make sure the coaxial cables are soldered onto their PL259 or BNC plugs correctly.
3. Check if the radio system needs an "earth"/"ground plane"/anode connection.
4. It is MOST IMPORTANT that the power from the marine radio is efficiently radiated through the antenna. Check using a vswr/swr meter.

Most radios will receive a signal using a length of wire, BUT a badly tuned antenna or faulty coaxial cable will not allow your signal to transmit efficiently and will damage the power output transistor stage of your radio rendering it useless.
If you measure a high vswr reading DO NOT TRANSMIT - YOU WILL DAMAGE YOUR RADIO.

Finally, if you are prepared to pay big bucks for a radio, make sure you pay for a good quality antenna and coax.

Hope this helps.

Festinghouse · 29 January 2013, 08:37

on the coax side, make sure the outer braid doesnt short to the centre core - look through the hole in the side of the plug to check that the braid is well out of the way, or better still check using a multi meter.

Ribochet · 29 January 2013, 08:47

Quote:

Originally Posted by Xk59D

i assume i have a problem in the system somewhere but not sure where to start, open to ways to proceed here?
remembering i can receive ok i'm not sure?
cheers

Just got my radio back after getting a new mic fitted -now 100% - great service from Geoff at Icom

City Radio · 29 January 2013, 23:44

Two excellent points made:
1. Ensure there isn't a short between the core and the braid of the coax (a common fault). This can be checked either with a swr meter and/or a multimeter.
2. ICOM marine radio's are well built and can be easily repaired (in most cases). They are also easy to re-programme (for change of owner MMSI number) by any good ICOM service centre.
If you plan on buying a new fixed marine radio, ensure it is a well recognised brand. If looked after it, any good radio can last for over 20 years or more. Money well spent.

If you are planning to fit a radio to your rib/boat, ensure you follow the manual instructions. If you are unsure about anything, just ask. Advice from forums like this one is free and most members are sure to help.

Xk59D · 30 January 2013, 01:28

not had a chance to look yet folks, weather has been shocking as no doubt most know.

cheers