weak vhf radio

[mmmouse]

did a radio check with vmr the other day...radio worked fine at close range but transmission and receiving got steadily weaker to virtually unreadable within just a few extra miles....radio was on 25w power setting...one for the techo's!!!???

[jimbamb]

Not a techo but have had experience with cb radios with same problem. Cause was too small a fuse in the feed line(2amp) Replaced fuse with 10 amp problem solved.
COULD be your problem
Jim

[myusernam]

check your power cable carefully. any terminations or inline fuses are the prime suspect. Highly recommend you reterminate the lot right back to the battery with some decent size cable. Use the best waterproof inline fuse holder you can find and spray some stuff in there to stop corrosion. vaseline will also do.

[testlab]

As above, check the power cables and fuse holders. The fuse value should be between 3A and 5A (10A is way too much).

When you do your close in radio check, ask what the readibility is. Is it
(a) crystal clear but low in signal strength, or
(b) is it muffled/distorted and low on signal strength?

If (a) then the antenna cable, connectors or the antenna itself are probably faulty. Check the antenna connectors to see if the coaxial cable is pulling away from the plug. If so its probably stuffed. Same with the feed point at the base of the antenna.

Look at the antenna and if there are deep nicks, cracks or stripping of the outer expoxy or wrap then it needs replacing as salt water will have gotten in and buggered it.

If (b) then it is a power problem to the radio or the output amplifier in the radio is possibly faulty. You can check the power cables, switches and fuse holders yourself.

If you suspect the radio take it to a mates boat and hook it up to his aerial and power and make a radio check call from the driveway (assuming you're not too close to the VMR). Or borrow a mates radio and try it on your setup when at sea.

Hopefully this will save you mucking about replacing stuff that isn't broken.

Cheers.

PS: The bad reception is a strong hint its the antenna or antenna cable. The radio uses hardly any power to receive so bodgy power wiring won't affect receiving as much as transmitting. A dodgy aerial affects both transmission and reception.

[Bros]

Were you on a Simplex channel?

[mmmouse]

thanks testlab will check that all out...vmr operator said 4 by 4 when first transmitted?????? doesn't that go back to the old days when radios had needles?? i have always said things like "received you loud and clear" 'cause i don't know exactly what "4 by 4" or "5 by 5" actually means...

yeah bro initially on ch 16 and then tried the repeater on 82 both the same

[Bros]

Sounds like it is not the operation just a radio problem. Make up a lead with alligator clips on one end and the radio power plug on the end and an inline fuse and connect to to your battery and radio. See if this makes any difference. Use this connection as a spare part to carry.
If this makes no difference go to the antenna

[testlab]

thanks testlab will check that all out...vmr operator said 4 by 4 when first transmitted?????? doesn't that go back to the old days when radios had needles?? i have always said things like "received you loud and clear" 'cause i don't know exactly what "4 by 4" or "5 by 5" actually means...

yeah bro initially on ch 16 and then tried the repeater on 82 both the same


First number relates to signal strength. You can gauge this by ear by listening to how much background "hash" there is behind the perons voice.

Strength 1 being a lot of noise with the persons voice barely punching through. Strength 5 means there is no background hash at all - if the VMR operator keyed the mic and didn't speak you would hear perfect silence (of an unmodlated carrier signal).

With a bit of experience its eay to judge signal strength by ear, asuuming your radio gear is functioning properly.

The second digit is readability. If the persons voice is perfectly intelligible its a '5' decreasng to '1' which would be something like listening to Bernie Fraser or the Swedish Chef or the Chipmunks talking underwater with a mouthful of marbes.

So.. for example...

A 5 x 5 means no background noise whatsoever and perfectly clear speech.

A 1 x 4 means a signal is really noisy but the voice still carries over the top even though the signal is very weak (like at extreme range).

A 3 x 3 would be quite usuable but not outstanding in any way.

A 5 x 1 would mean a noise free signal (between the words) but the voice quality is so bad its completely useless.

VHF is FM so there is little you can do to improve transmitting quality. Its all fixed at manufacture. But pro-type HF sets allow adjustment of voice amplitude (gain) and a number of other tricks (compression and so forth) to improve readability on incredibly small signal strengths over very long distances. So when stations first talk to each other they give a signal check at the beginning to allow the "other guy" to better tune his transmitter if possible (and your receiver too).

The "5 x 5" method comes from aviation communication. Aviation radios don't have S meters - S meters on HF radio recivers show signal strength from 0-9. So 9 x 5 is equivalent to 5 x 5.

And after all that... for VHF "loud and clear" accomplishes the same thing.

Cheers
Dave.

[La Vida]

what type of antenna do you have?

[myusernam]

how far away were you from the coast guard when you had problems?

[finga]

The bad reception is a strong hint its the antenna or antenna cable. The radio uses hardly any power to receive so bodgy power wiring won't affect receiving as much as transmitting. A dodgy aerial affects both transmission and reception.
Yep...sure is. I'd be looking at the aerial first.

Have you got one of those am/fm splitters in the aerial cable??

Does the radio turn itself off?
What sort of radio is it as a lot turn themselves off when voltages gets too low.

[mmmouse]

ok...here goes..by 5 miles distant radio very hard to read

aerial is a pacific aerials brand...no other info..looks just like a mini outrigger pole...fibrelass.. with the cable entering at the bottom of the aerial

the radio is a uniden MC615 (otc auto-seaphone)

handset is a uniden AMX110

radio hasn't been turning off..both batteries are on full charge..in line fuse is a 10 amp glass fuse

all connections and fuse are nice and shiny, no corrosion anywhere and the same for the aerial connection into the radio

am/fm splitter...sorry no idea

there is a bout 15ft of aerial cable all zippy tied up together tight in an effort to tidy the installation...could that be causing interference?

[finga]

Have you got an am/fm radio in the boat?
When you press the transmit button how many led's come on?

If the aerial is the same age as the radio then I'd be getting the whole outfit tested.
Those radio's are getting very long in the tooth but I'm still thinking aerial but someone with the correct test equipment will be able to tell you in about 5 minutes what the problem is.

[mmmouse]

no am/fm radio onboard.....yeah i can see it's not the latest model and realise i will probably have to replace it, probably sooner rather than later, but money's tight right now so looking at all options. i do have a handheld as well so a replacement is a way off....mmmm...maybe after a 4 stroke.......lol

[testlab]

So at 5 miles its hard to read someone talking to you but it gets better the closer you are?

If so I'd say its the aerial or lead. Where the cable is bundled have a look at the bends and see if the sun has caused the outer jacket to harden and split.

It is a pretty old radio... its possible its got age related internal problems but I'd check it on someone elses rig and if it works OK then keep it. If you don't want DSC then there's no need to replace it.

If you have no ability to try it on someone elses boat and you can't find a friendly tech who'll check it on the cheap then drop me a private message.

[captain rednut]

sounds like you are on a canadian frequency, check for the word ( int ) on the screen, or if it says usa or can thats the problem.
cheers cr