samsturdy said..
I have a Uniden UM425 VHF radio that does not turn on. There is power to the connector and the fuse is intact but
when switched on nothing lights up, it's dead. Is there someone around the Northern areas that can check it out
for me ?.

Did you pull the fuse and clean the terminals? Might just be corrosion. There also may be a second fuse inside the case.

Similar to Ramonas suggestion, those in line fuses can be unreliable. Also unless you actually tested the fuse with a meter it might still be sus. I found some that "look" ok through the glass but are open. Also check the plug that enters the radio.

Having asked a few people locally it seems the consensus is 'throw it away and buy a new one' apparently they're
too expensive to fix. I'll have a look online.

crustysailor said..
SS, i have the same one, but it had no signal.
Powers up ok, and when I checked it a few months ago, theres no internal power fuse, just the external.

I bought a new one rather than repair it. No one does board level repairs these days much anyhow.

If you want to have a play though, you're welcome to have my old unit and see if you can make 1 from 2.

Thanks for the offer crusty but I think I'll do the same as you and go for a newie.

I recently went through the the radio saga. My GME would work perfectly in the harbour but as soon as I got outside nobody could hear me.
I checked everything about a million times. Went up the mast a few times. It had me convinced that there was an issue with the antenna.
Eventually and much to my disgust I had to bite the bullet and actually pay someone to come down and check it out. This first year apprentice turned up and hooked his meter into the antenna lines. Still nothing. After a bit more ******ing about he came to the conclusion that the batteries in his meter were in backwards. ??
He switched the batteries around in the meter. Still nothing. After a lot more ******ing around which involved ripping half of the boat apart and another hour of my time checking what I had already checked a dozen times he stands up, scratches his head and declares "I don't know what's wrong. It should be working."
I never pay anybody to do work on my boat. This was the first time I couldn't work out what was wrong.
I gave them the hundred bucks for their call out fee and got him off my boat.
I then drove down to RTM and bought a brand new Uniden radio for $199. Hooked it up. Problem solved.
I don't think I will ever pay anyone else to work on my boat again.

My advice to you is get down to RTM and buy a new radio it will cost more than it's worth to have someone look at it.

samsturdy said..
Thanks Shags. As a Pittwater sailor I don't need the extra apps, just peace of mind that should something
go astray I can call for help. I know I could use my mobile phone but the battery always seems to be flat.

Good story Raps. I've decided to go new anyway, it seems radio innards are mysterious.

Sam, before you throw it double check that previously some idiot hasn't installed it to replace a dud one and wired the supplied fuse to the existing wires after cutting off the old radio connection, thus having two inline concealed fuses for the one unit. Been there done that, took me ages to find it.

crustysailor said..
since it sounds like Sam may be sorted, does anyone have any thoughts regarding possible damage to a VHF powering it on without an antenna connected?

I find it surprising that with a modern radio any damage could occur, but in tracing may own issue of no signal in or out, it may be what had happened at some stage.

There's no warnings in any manuals I have read, but it was suggested to me that the unit could be damaged this way. Certainly when I replaced the VHF again, with the existing antenna and wiring, I had perfectly good communication straight away.

If it does prove to have some truth, Sam you might want to take note when you do the changeover not to power i the new one up inadvertently.

Hi Crusty

From my limited radio knowledge I believe the only way you may cause internal damage to a radio is by transmitting without the aerial connected

If you haven't hit the transmit button I don't see how it could damage it

Regards Don

Thought I would post here instead of opening a new one.
I have been using a GME hand held for over two years and the battery finally died . As I have got into the habit of advising VMR whenever I go out as I solo I use it a fair bit. Anyway as well as getting a new battery
( not cheap) I bought a Uniden UM 455 vhf DSC , axis mfv3 Ariel and installed with the intention of registering for an MMSI number.
Yesterday I signed on with VMR with the hand held and signed off on the Uniden. Although VMR head my initial call on the Uniden and I could hear them 20/20 on 82=
they advised I was barely audible in asking to take me off the board.
I was using 1kw assuming that would be sufficient.

Any ideas why ?
Could it be because I had the hand held turned on beside the Uniden?

Bananabender said..
Thought I would post here instead of opening a new one.
I have been using a GME hand held for over two years and the battery finally died . As I have got into the habit of advising VMR whenever I go out as I solo I use it a fair bit. Anyway as well as getting a new battery
( not cheap) I bought a Uniden UM 455 vhf DSC , axis mfv3 Ariel and installed with the intention of registering for an MMSI number.
Yesterday I signed on with VMR with the hand held and signed off on the Uniden. Although VMR head my initial call on the Uniden and I could hear them 20/20 on 82=
they advised I was barely audible in asking to take me off the board.
I was using 1kw assuming that would be sufficient.

Any ideas why ?
Could it be because I had the hand held turned on beside the Uniden?

Hi BB,
What is the output power on the handheld, ie: 1 watt? I'm trying to work out the difference.
The dinky little antennas on a hand held are usually a 0db gain antenna, so not much grunt. Unless you have a lot of coax, and its 6mm not 1/2 inch, to your antenna on the new system, the 455 should kick the bejeesus out of your handheld in range.

Have you got an external antenna output on the handheld? Screw it to your new antenna and test with the handheld, see if it makes a difference. I have some SMA to N type adaptors to do the funky little connector to a big one, I can post you one if its any help.

Regards antenna position and crosstalk, yes, this is an issue with any antenna system. But I don't think this may apply in your case.
The standard rule of thumb with wireless links is that even before you transmit speech or data, the transmitter is generating a frequency. When you talk or push information, you modulate that carrier frequency wave.
Two antennas that are transmitting on the same frequency will degrade the quality of the signal on each one, as the output power from Antenna A will be picked up by Antenna B as noise. As your signal quality is dictated by the difference between its peak power and the noise "floor" (think static) , it is very important to try and minimise the noise floor as much as it is in having lots of signal power (1w or 25w) . Winding up the output power amplifies the noise floor as well as the peak signal, so look for a noise issue if output power doesn't fix it. A bad noise floor can degrade the quality of the signal even at 25 w to being next to useless.

Dodgy connectors, bad coax, corrosion and proximity of antennas can all contribute to a high noise.

With that in mind, the reason I say that antenna position is unlikely to be the cause in your case is because I don't think VHF transits even a carrier frequency until you push the talk button. If so, no naughty crosstalk, or noise, can occur unless you push both transmit buttons at once.
If this is the case, you wouldn't care if you have 5 antennas within a few inches.

Anyone know if VHF radios are actively transmitting a frequency all the time?

Edit: A simple test would be use the new unit with the handlehd on. Repeat with the handheld off. Difference?

Datawiz said..
A VHF radio will only be transmitting whilst you have the Press-to-Talk (PTT) button pressed

Thanks Datawiz!
So if it doesn't emit any radio frequency without the PTT button being pressed, then there can be no interference.

Ramona , The aerial is mounted on the transom. I'll recheck all connections .The only other item on the transom is the solar panel. Reception is great.
SB
Handheld output 1 low , 4.8 HI . I transmit HI and the receiving end has never reported an issue. VMR confirmed a couple of weeks ago they were receiving ok. Handheld reception sometimes scratchy but normally acceptable for where I go.
Re Uniden I assumed that if reception was 20/20 connections must be ok. At the time all electrics except that to the depth ,radio and solar to battery turned off. The hand held was next to Uniden switched on on same channel but not transmitting.
The aerial is advertised as compatible with the radio but I have no idea about coax size. Actually I was surprised how thin it was compared to the old cable . Length of cable 4.5 metres .
I'll recheck everything again and retest with all other power except solar off.

I'm seriously considering getting a 5 watt handheld VHF. Is there a point on the radio that will connect to my external antenna ??

Bananabender said..
Ramona , The aerial is mounted on the transom. I'll recheck all connections .The only other item on the transom is the solar panel. Reception is great.
SB
Handheld output 1 low , 4.8 HI . I transmit HI and the receiving end has never reported an issue. VMR confirmed a couple of weeks ago they were receiving ok. Handheld reception sometimes scratchy but normally acceptable for where I go.
Re Uniden I assumed that if reception was 20/20 connections must be ok. At the time all electrics except that to the depth ,radio and solar to battery turned off. The hand held was next to Uniden switched on on same channel but not transmitting.
The aerial is advertised as compatible with the radio but I have no idea about coax size. Actually I was surprised how thin it was compared to the old cable . Length of cable 4.5 metres .
I'll recheck everything again and retest with all other power except solar off.

BB,
50 ohm coax for VHF radios comes in 6mm and 12.5mm (commonly known as half inch). The fat one has a lot less loss.
6mm coax is fine for 4.5mtrs though. 12.5mm is for run lengths like going up a mast.
Dumb question; was the new antenna mounted vertically when you tested?

shaggybaxter said..
Sam,
Most handhelds' antenna screws off, and you can connect a coaxial tail to the port to an external antenna. Some units have a dedicated port (rare), most only support a microphone and earpiece as their external connections. .
My cheap Uniden's don't have any interfacing, the antenna is fixed.
It's pretty rare to ever add a dedicated base antenna to a handheld though as the coaxial tail make them arkward, It's usually used to put a bigger gain dongle aerial directly onto the handheld.

Thanks for that Shags.

I've resurrected this thread because I'm about to buy a replacement radio after all this time and I see there's a
special on at Whitworths for a Standard Horizon GX300E for $149.00. That's a $100 discount. At a normal price
of $249.00 it's not a cheap radio ( a Uniden UM455 is $229.90. ) . So do you reckon I'm alright to go ahead and
purchase this ?.