VHF transmits but won't receive, possible aerial problem?

[MJBorley]

The VHF on my recently acquired Seamaster 23 yacht doesn’t work. It will transmit OK but won’t receive anything. It was on for 8 hours while we were sailing in the Rivers Orwell and Stour and in that time it didn’t receive a single transmission on channel 16. I subsequently tested it using my hand-held VHF and established that it transmits OK but doesn’t pick up transmissions from the hand-held. The speaker will hiss if the squelch isn’t adjusted correctly (so the speaker is working) and on several occasions it went “beep-beep-beep”, but never any speech.

I disconnected the aerial from the VHF and measured the resistance between the outer metal knurled connector ring (which I believe is connected to the cable shield) and the inner connector and it was approximately 1,000 kilo ohms. My knowledge of electronics is not good. I expected there to be infinite resistance between the shield and the inner core. I know 1,000 kilo ohms is a lot, but its not infinite.

My question is, does this indicate there is a problem with the aerial, or is it to be expected? If it indicates there is a problem, is my experience of being able to transmit but not receive consistent with the problem? I haven’t been up the mast to check the wiring at the aerial end (that will have to wait to the end of the season when the mast is de-stepped) but the nav lights don’t work either so I expect the wiring in the mast to be in a poor condition and it may be that the aerial has suffered a similar lack of maintenance in previous ownership. The VHF radio is reasonably new, which doesn’t mean it can’t be faulty, but my first suspicions are on the aerial.

 

[Lon nan Gruagach]

The VHF on my recently acquired Seamaster 23 yacht doesn’t work. It will transmit OK but won’t receive anything. It was on for 8 hours while we were sailing in the Rivers Orwell and Stour and in that time it didn’t receive a single transmission on channel 16. I subsequently tested it using my hand-held VHF and established that it transmits OK but doesn’t pick up transmissions from the hand-held. The speaker will hiss if the squelch isn’t adjusted correctly (so the speaker is working) and on several occasions it went “beep-beep-beep”, but never any speech.

I disconnected the aerial from the VHF and measured the resistance between the outer metal knurled connector ring (which I believe is connected to the cable shield) and the inner connector and it was approximately 1,000 kilo ohms. My knowledge of electronics is not good. I expected there to be infinite resistance between the shield and the inner core. I know 1,000 kilo ohms is a lot, but its not infinite.

My question is, does this indicate there is a problem with the aerial, or is it to be expected? If it indicates there is a problem, is my experience of being able to transmit but not receive consistent with the problem? I haven’t been up the mast to check the wiring at the aerial end (that will have to wait to the end of the season when the mast is de-stepped) but the nav lights don’t work either so I expect the wiring in the mast to be in a poor condition and it may be that the aerial has suffered a similar lack of maintenance in previous ownership. The VHF radio is reasonably new, which doesn’t mean it can’t be faulty, but my first suspicions are on the aerial.

Dont expect to get any sensible readings of aerial resistance, they are only concerned with what happens at radio frequencies. There is often quite a lot of electronic gubbins in the base.
To properly test your aerial you need a vSWR meter, best borrow one and the owner that knows how to use it.
If you get reasonable transmission (range and clarity) then your problem is almost certainly in the receiver circuit in your VHF box.

 

[savageseadog]

If it's one of the Icom sets then there is an issue on some models the filters degrading resulting in Tx but poor Rx. Icom repair it for free!

 

[matthewriches]

Had this on my iCom. I think, but can remember 100%, that it is something to do with ceramic filters.

Happy to run it up on the bench here if you are still struggling and then see what can be done?

 

[Plum]

The VHF on my recently acquired Seamaster 23 yacht doesn’t work. It will transmit OK but won’t receive anything. It was on for 8 hours while we were sailing in the Rivers Orwell and Stour and in that time it didn’t receive a single transmission on channel 16. I subsequently tested it using my hand-held VHF and established that it transmits OK but doesn’t pick up transmissions from the hand-held. The speaker will hiss if the squelch isn’t adjusted correctly (so the speaker is working) and on several occasions it went “beep-beep-beep”, but never any speech.

I disconnected the aerial from the VHF and measured the resistance between the outer metal knurled connector ring (which I believe is connected to the cable shield) and the inner connector and it was approximately 1,000 kilo ohms. My knowledge of electronics is not good. I expected there to be infinite resistance between the shield and the inner core. I know 1,000 kilo ohms is a lot, but its not infinite.

My question is, does this indicate there is a problem with the aerial, or is it to be expected? If it indicates there is a problem, is my experience of being able to transmit but not receive consistent with the problem? I haven’t been up the mast to check the wiring at the aerial end (that will have to wait to the end of the season when the mast is de-stepped) but the nav lights don’t work either so I expect the wiring in the mast to be in a poor condition and it may be that the aerial has suffered a similar lack of maintenance in previous ownership. The VHF radio is reasonably new, which doesn’t mean it can’t be faulty, but my first suspicions are on the aerial.

I had a receive only problem with my Standard Horizin VHF recently although in my case i had background noise obliterating the receive audio. SH said very unlikely to be the aerial checked it out for me for free saying no problem. Turned out it was a USB charger plugged into a cigar lighter socket on board. After telling SH they said the usb charger was probably afecting the ceramic filters in the receive circuit. Bought a different make of USB charger and problem solved.

Www.solocoastalsailing.co.uk

 

[William_H]

Essentially if you have noise with squelch open but can not receive any signal from a hand held on board then you have a receiver problem. Either return to to makers for repair or buy a new radio. Paying for labour to repair can be just too expensive. good luck olewill

 

[<152587>]

Dont expect to get any sensible readings of aerial resistance, they are only concerned with what happens at radio frequencies. There is often quite a lot of electronic gubbins in the base.
To properly test your aerial you need a vSWR meter, best borrow one and the owner that knows how to use it.
If you get reasonable transmission (range and clarity) then your problem is almost certainly in the receiver circuit in your VHF box.

Suggest you read a copy of installation instructions. Some makes of radio antennae do have a 10k resistance between core and shield, and indeed the instructions encourage you to measure this as a way of ensuring continuity.

 

[Lon nan Gruagach]

Suggest you read a copy of installation instructions. Some makes of radio antennae do have a 10k resistance between core and shield, and indeed the instructions encourage you to measure this as a way of ensuring continuity.

Sure specific makes will have specific characteristics, few if any bearing any resemblance to the characteristic impedance needed to match the transmission line. But without that specific knowledge dc resistance of an aerial isn't much use.

 

[<152587>]

Sure specific makes will have specific characteristics, few if any bearing any resemblance to the characteristic impedance needed to match the transmission line. But without that specific knowledge dc resistance of an aerial isn't much use.

A simple test that takes one problem out of the equation.

 

[Lon nan Gruagach]

A simple test that takes one problem out of the equation.

Its a simple test that will identify some of the potential problems. If the system passes the test you must still use a SWR test to eliminate antenna and coax faults.

 

[PaulRainbow]

The VHF on my recently acquired Seamaster 23 yacht doesn’t work. It will transmit OK but won’t receive anything. It was on for 8 hours while we were sailing in the Rivers Orwell and Stour.

Where do you keep the boat ? If it's in one of the Orwell marinas or if you can call into Shotley i'll check the antenna with my VSWR meter for you, no charge.

 

[PeterR]

At the end of last season I developed exactly the same problem with both my main VHF and handheld. I could transmit successfully over at least several miles range but I could not receive whatever the range. The fault was the same in both cases and was the caused by failure of the filters. The handheld was an ICOM who repaired it free of charge. The main radio was a Raymarine who charged £160 for a repair.

 

[LadyInBed]

A fairly low cost way to check the antenna Rx would be to buy a plug and a couple of meters of coax, strip about a meter of screen off, connect to VHF then transmit on H/H.
Alternatively, do a Radio Check with CG

 

[alant]

The VHF on my recently acquired Seamaster 23 yacht doesn’t work. It will transmit OK but won’t receive anything. It was on for 8 hours while we were sailing in the Rivers Orwell and Stour and in that time it didn’t receive a single transmission on channel 16. I subsequently tested it using my hand-held VHF and established that it transmits OK but doesn’t pick up transmissions from the hand-held. The speaker will hiss if the squelch isn’t adjusted correctly (so the speaker is working) and on several occasions it went “beep-beep-beep”, but never any speech.

I disconnected the aerial from the VHF and measured the resistance between the outer metal knurled connector ring (which I believe is connected to the cable shield) and the inner connector and it was approximately 1,000 kilo ohms. My knowledge of electronics is not good. I expected there to be infinite resistance between the shield and the inner core. I know 1,000 kilo ohms is a lot, but its not infinite.

My question is, does this indicate there is a problem with the aerial, or is it to be expected? If it indicates there is a problem, is my experience of being able to transmit but not receive consistent with the problem? I haven’t been up the mast to check the wiring at the aerial end (that will have to wait to the end of the season when the mast is de-stepped) but the nav lights don’t work either so I expect the wiring in the mast to be in a poor condition and it may be that the aerial has suffered a similar lack of maintenance in previous ownership. The VHF radio is reasonably new, which doesn’t mean it can’t be faulty, but my first suspicions are on the aerial.

Do you know you are definitely being received?