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 @

Thanks for all the input!

Turns out (after spending more time on it than the 1980's
VHF is worth) that it was the loudspeaker that had failed.
Nice reception with earphones conected to the speaker wires.

So where do I get a replacement speaker?

Thanks!

Well, Radio Shack might have something.

Simplest solution would be to use an external shielded speaker (e.g.,
West Marine) that you could plug in to the radio. Does the radio have an
external speaker jack?

Chuck

Chris wrote:
Thanks for all the input!

Turns out (after spending more time on it than the 1980's
VHF is worth) that it was the loudspeaker that had failed.
Nice reception with earphones conected to the speaker wires.

So where do I get a replacement speaker?

Thanks!

any good electronics shop should be able to help

Name one in LA.
Radio Shack isn't it: "Uuh, raw speakers? Not any more, sorry."