I have a VHF radio connected to an antenna on the mast,
which does not make a sound. It has power, the lights on
it come on, but not a sound on any channel.

I suspect that the cable leading to the antenna is bad,
disconnected, or whatever. (Does this sound like the likely
cause?)

To check this, what do I have to measure in antenna/cable:
Impedance? What does an ok antenna cable show?

Thanks!

"Chris" wrote in message
oups.com...
I have a VHF radio connected to an antenna on the mast,
which does not make a sound. It has power, the lights on
it come on, but not a sound on any channel.

I suspect that the cable leading to the antenna is bad,
disconnected, or whatever. (Does this sound like the likely
cause?)

To check this, what do I have to measure in antenna/cable:
Impedance? What does an ok antenna cable show?

Or you can borrow a friends (known good) spare antenna and plug it in for a
quick test.

Chris wrote:
I have a VHF radio connected to an antenna on the mast,
which does not make a sound. It has power, the lights on
it come on, but not a sound on any channel.

I suspect that the cable leading to the antenna is bad,
disconnected, or whatever. (Does this sound like the likely
cause?)

To check this, what do I have to measure in antenna/cable:
Impedance? What does an ok antenna cable show?

Thanks!

A spare, portable antennae is quite common since the masthead antennae
is vulnerable to a number of mishaps; I carry a suction cup version.
This could be a good time to invest, or you should be able to find
someone that has one. Another possibility is a signal strength meter.

Anything I can do with the multimeter I have here?

Chris,
In a Word - NO
The antenna on the mast may well exhibit a very low DC resistance.
The spare antenna suggestion was the best. If you do not have one.
plug any piece of wire into the center of the antenna connection and set
up to the local weather tx.

If you get something, you have an antenna problem. Most of the time,
this is cable damage (like getting the coax under the mast when it was
stepped).

If you still can not get any weather channel, undo the screws on the
bracket (save them) and frizby the whole thing (repair is seldom
ecomomicly viable).

At the price of a bench hour, it is seldom that a tech can complete a
diagnosis for less that half the cost of replacement.

Matt Colie

Chris wrote:
Anything I can do with the multimeter I have here?

I'd certainly check to see if the center conductor is shorted to the shield.
(Near zero ohms with the cable disconnected from the transceiver.) That was
a common failure mode on the old Nike missile system. Where the cable makes
a sharp turn the center conductor would push thru (slowly) the insulation.
Wiggling the cable to detect an intermittent short is also something I would
try.

Of course, if it is shorted and you tried to transmit, you may have fried
the transmitter.

Roger

http://home.insightbb.com/~derbyrm

"Chris" wrote in message
ups.com...

Anything I can do with the multimeter I have here?

In article i35Rf.817913$x96.597697@attbi_s72,
"derbyrm" wrote:

I'd certainly check to see if the center conductor is shorted to the shield.
(Near zero ohms with the cable disconnected from the transceiver.) That was
a common failure mode on the old Nike missile system. Where the cable makes
a sharp turn the center conductor would push thru (slowly) the insulation.
Wiggling the cable to detect an intermittent short is also something I would
try.

Of course, if it is shorted and you tried to transmit, you may have fried
the transmitter.

Roger

http://home.insightbb.com/~derbyrm

"Chris" wrote in message
ups.com...

Anything I can do with the multimeter I have here?




This would NOT nessesarily prove anything, one way or the other.
Many VHF antennas are designed to have a DC Ground on the Center
Conductor of the coax connection. Also 99% of the VHF Marine
Radios on the market for the last decade or so, have Power Foldback
Circuits that detect High SWR on the Feedline and reduce the Power
Output so as to not over dissapate the RF Final Amplifier.

Bruce in alaska
--
add a 2 before @

Interesting. The aircraft whips seem to get by without a loading coil at
the antenna. Anyway, all that means is that you disconnect both ends of the
cable before checking.

Roger

http://home.insightbb.com/~derbyrm

"Bruce in Alaska" wrote in message
...
In article i35Rf.817913$x96.597697@attbi_s72,
"derbyrm" wrote:

I'd certainly check to see if the center conductor is shorted to the
shield.
(Near zero ohms with the cable disconnected from the transceiver.) That
was
a common failure mode on the old Nike missile system. Where the cable
makes
a sharp turn the center conductor would push thru (slowly) the
insulation.
Wiggling the cable to detect an intermittent short is also something I
would
try.

Of course, if it is shorted and you tried to transmit, you may have fried
the transmitter.

Roger

http://home.insightbb.com/~derbyrm

"Chris" wrote in message
ups.com...

Anything I can do with the multimeter I have here?




This would NOT nessesarily prove anything, one way or the other.
Many VHF antennas are designed to have a DC Ground on the Center
Conductor of the coax connection. Also 99% of the VHF Marine
Radios on the market for the last decade or so, have Power Foldback
Circuits that detect High SWR on the Feedline and reduce the Power
Output so as to not over dissapate the RF Final Amplifier.

Bruce in alaska
--
add a 2 before @

Roger,
This is correct.

I suspect he is not not to disconnect the antenna element as it is a
bosun's chair ride away.

By the larger part, an aircraft comm antenna is a simple 1/4wave.

Matt Colie


derbyrm wrote:
Interesting. The aircraft whips seem to get by without a loading coil at
the antenna. Anyway, all that means is that you disconnect both ends of the
cable before checking.

Roger

http://home.insightbb.com/~derbyrm

"Bruce in Alaska" wrote in message
...

In article i35Rf.817913$x96.597697@attbi_s72,
"derbyrm" wrote:


I'd certainly check to see if the center conductor is shorted to the
shield.
(Near zero ohms with the cable disconnected from the transceiver.) That
was
a common failure mode on the old Nike missile system. Where the cable
makes
a sharp turn the center conductor would push thru (slowly) the
insulation.
Wiggling the cable to detect an intermittent short is also something I
would
try.

Of course, if it is shorted and you tried to transmit, you may have fried
the transmitter.

Roger

http://home.insightbb.com/~derbyrm

"Chris" wrote in message
groups.com...

Anything I can do with the multimeter I have here?



This would NOT nessesarily prove anything, one way or the other.
Many VHF antennas are designed to have a DC Ground on the Center
Conductor of the coax connection. Also 99% of the VHF Marine
Radios on the market for the last decade or so, have Power Foldback
Circuits that detect High SWR on the Feedline and reduce the Power
Output so as to not over dissapate the RF Final Amplifier.

Bruce in alaska
--
add a 2 before @

Same ride he'll have if the substitute antenna or bit of brazing rod gives a
signal.

Yep, lambda over four minus 10% for end effects. (But I checked the spare
in the basement to be sure. It's been fifty years since I let my second
class phone license lapse.)

What do you do to prevent lightning or St. Elmo's fire from frying the
transceiver? Would an MOV built in as part of the impedance matching be
effective?

Roger

http://home.insightbb.com/~derbyrm

"Matt Colie" wrote in message
...
Roger,
This is correct.

I suspect he is not not to disconnect the antenna element as it is a
bosun's chair ride away.

By the larger part, an aircraft comm antenna is a simple 1/4wave.

Matt Colie


derbyrm wrote:
Interesting. The aircraft whips seem to get by without a loading coil at
the antenna. Anyway, all that means is that you disconnect both ends of
the cable before checking.

Roger

http://home.insightbb.com/~derbyrm

"Bruce in Alaska" wrote in message
...

In article i35Rf.817913$x96.597697@attbi_s72,
"derbyrm" wrote:


I'd certainly check to see if the center conductor is shorted to the
shield.
(Near zero ohms with the cable disconnected from the transceiver.) That
was
a common failure mode on the old Nike missile system. Where the cable
makes
a sharp turn the center conductor would push thru (slowly) the
insulation.
Wiggling the cable to detect an intermittent short is also something I
would
try.

Of course, if it is shorted and you tried to transmit, you may have
fried
the transmitter.

Roger

http://home.insightbb.com/~derbyrm

"Chris" wrote in message
egroups.com...

Anything I can do with the multimeter I have here?



This would NOT nessesarily prove anything, one way or the other.
Many VHF antennas are designed to have a DC Ground on the Center
Conductor of the coax connection. Also 99% of the VHF Marine
Radios on the market for the last decade or so, have Power Foldback
Circuits that detect High SWR on the Feedline and reduce the Power
Output so as to not over dissapate the RF Final Amplifier.

Bruce in alaska
--
add a 2 before @