VHF radio-to receive or not to receive

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celtictemple

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My VHF/DSI radio has decided that it will transmit Ok but won't receive any incoming calls- OK if I need help as other boats may hear, but I won't know if I am going to get any! The antenna blew down a few weeks ago but the wire seemed to be OK and I re attached it. I don't understand how I can transmit and not receive as I naively thought the antenna did both. Maybe someone more technically aware can point me in the right direction?
Cheers
 
The aerial does do both, it is used for transmitting and receiving.

The difference is in the signal power. On transmit your transmitter is generating something around 25 watts. On receive it is listening for signals in the realms of microvolts ie. millions of times less that the transmit.

Leaving aside all the technicalities its is a lot easier for the 25 watts to barge its way out through the most ropey of aerial systems than it is for a few millivolts to find their way back.

It sounds like time to thoroughly check the system, cables, connectors, aerial etc.

Martin
 
thanks Martin- I was hoping that I didn't need to check everything-but I guess you are right. How does one check the quality of the cable from the top to the point where it enters the radio since most is inside the bars and rails and will nor budge if I try to pull it out!?
 
OK- There is squelch from the radio, it certainly transmits (but it does this without the antenna connected! -as confirmed using hand held radio)-I have now sourced a brand new antenna which I have connected to the radio but still cannot receive any transmission from my hand held 2 metres away-any suggestions. The radio is less than 12 months old so should be OK but could it be just duff? It did work up till a few weeks ago whentthe antenna blew down in a storm
 
when the PTT on the mic is pressed the receive is turned of. A broken wire from the mic can stop the radio audio on receive.
 
"Leaving aside all the technicalities its is a lot easier for the 25 watts to barge its way out"

Sorry have to disagree there.With manky aerial you will hear a lot further than send.
Your radio can receive on a bit of wet string and even if a dead short between the braid and the central copper wire it will pick up transmissions.Your 25w will not barge its way out but go directly to earth giving possibly a few tens yards if that.
My guess,even on new radio(and esp on old stuff) is speaker cone.Plug in a ext speaker and see what happens.The little 3,5mm spkr ext socket on the back can also go faulty.
Also many radios do not require a contact via mike to receive.
 
Stupid question I hope, but your not testing it on one of the duplex channels are you e.g marina channel 80, you'll never hear a reply from another boat just the marina:D
 
celtictemple said:
My VHF/DSI radio has decided that it will transmit Ok but won't receive any incoming calls- OK if I need help as other boats may hear, but I won't know if I am going to get any! The antenna blew down a few weeks ago but the wire seemed to be OK and I re attached it. I don't understand how I can transmit and not receive as I naively thought the antenna did both. Maybe someone more technically aware can point me in the right direction?
Cheers
Click to expand...

return it under warranty.
 
I had exactly the same problem with my VHF a few months ago,
it was a Icom 411
send back to the dealer and was repaired under warranty,
(a electronics problem in the VHF transmit cirquit)
 
Celtictemple, did you manage to find a fix?

I have exactly the same problem on my Icom IC-M411. Transmits well but just stoped receiving. Get odd bit off real close stuff occasionally on some channels. It cant be the speaker as it makes plenty of noise when the squelch is turned down.
 
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