Hello,



I suspect that my VHF antenna is shot, I think it's open circuit.

I'm looking for a quick and easy way to verify it with an ohm meter.

I know that the 50 ohm impedance is an AC impedance

at RF frequencies. But I'm guessing a DC ohm meter should

measure something between a few 10s of ohms to a few hundreds

of ohms if the antenna was good.

I'm measuring ~ 10 meg ohms.



Time for a new antenna?



Thanks in advance,

Vin

"Vinny" wrote in message
. ..
Hello,



I suspect that my VHF antenna is shot, I think it's open circuit.

I'm looking for a quick and easy way to verify it with an ohm meter.

I know that the 50 ohm impedance is an AC impedance

at RF frequencies. But I'm guessing a DC ohm meter should

measure something between a few 10s of ohms to a few hundreds

of ohms if the antenna was good.

I'm measuring ~ 10 meg ohms.



Time for a new antenna?

Depending on the design, the VHF antennas that I'm familiar with will
read either "open" or "shorted" with an Ohmmeter. 10 megohms is a strange
reading for an antenna. Almost sounds like one that is supposed to read
"open" but has a little (or a lot) of water/corrosion someplace where it
doesn't do any good at all.
Old Chief Lynn, W7LTQ

Vinny wrote:
Hello,



I suspect that my VHF antenna is shot, I think it's open circuit.

I'm looking for a quick and easy way to verify it with an ohm meter.

I know that the 50 ohm impedance is an AC impedance

at RF frequencies. But I'm guessing a DC ohm meter should

measure something between a few 10s of ohms to a few hundreds

of ohms if the antenna was good.

I'm measuring ~ 10 meg ohms.



Time for a new antenna?



Thanks in advance,

Vin

Don't mess around with meters. If you are near a chandlers, buy an emergency
antenna. Try it out, if that does the trick, take it back and exchange it
for a permanent antenna. Any chandlers will oblige. Problem solved!

Dennis.

Vinny wrote:
Hello,



I suspect that my VHF antenna is shot, I think it's open circuit.

I'm looking for a quick and easy way to verify it with an ohm meter.

I know that the 50 ohm impedance is an AC impedance

at RF frequencies. But I'm guessing a DC ohm meter should

measure something between a few 10s of ohms to a few hundreds

of ohms if the antenna was good.

I'm measuring ~ 10 meg ohms.



Time for a new antenna?



Thanks in advance,

Vin



Why do you suspect the antenna is shot?

Are you measuring at the end of 70 feet of coax
attached to the antenna or directly at the antenna
terminals?

Chuck

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chuck wrote:
Vinny wrote:

Hello,



I suspect that my VHF antenna is shot, I think it's open circuit.

I'm looking for a quick and easy way to verify it with an ohm meter.

I know that the 50 ohm impedance is an AC impedance

at RF frequencies. But I'm guessing a DC ohm meter should

measure something between a few 10s of ohms to a few hundreds

of ohms if the antenna was good.

I'm measuring ~ 10 meg ohms.



Time for a new antenna?



Thanks in advance,

Vin



Why do you suspect the antenna is shot?

Are you measuring at the end of 70 feet of coax attached to the antenna
or directly at the antenna terminals?

Chuck

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Try to get a SWR meter. This will mesure the power that go's and gets
back to your transmitter.

--
Geert Maene.

Geert Maene wrote in news:gvvig.474444
:

Try to get a SWR meter. This will mesure the power that go's and gets
back to your transmitter.



http://www.walcottcb.com/valor-v6050...-watt-meter-p-
920.html

Don't forget to get a 3' coax jumper to hook the TX port to your radio.

Mount it permanently next to the radio by using two right-angle coax
adapters male to female. Screw them onto the meter so they go back into
two matching holes in the panel. If you make the holes a tight fit with
the PL-259 coax connectors, no mounting of the little meter is necessary.
Just leave it on the surface between the holes. That way you can check for
RF output power and antenna performance every time you use the radio...IF
the radio isn't mounted out in the weather the meter won't tolerate....

Works great.

I don't have a real good reason for suspecting the antenna except
that theDC resistance I measure is strange. I would expect it to be open
circuit or low resstance, not a few Meg ohms.
The VHF seems to receive OK and when I transmit, I know there
is power being generated beause it interferes with my portable
FM radio. Bu when I call for a radio check, I don't get a response.
It's an old antenna, it was on the boat when I bought it. There's no
markings left on it but it has a blue and green pin stripe near the base
which I think is shakespeare (sp?)

"chuck" wrote in message
...
Vinny wrote:
Hello,



I suspect that my VHF antenna is shot, I think it's open circuit.

I'm looking for a quick and easy way to verify it with an ohm meter.

I know that the 50 ohm impedance is an AC impedance

at RF frequencies. But I'm guessing a DC ohm meter should

measure something between a few 10s of ohms to a few hundreds

of ohms if the antenna was good.

I'm measuring ~ 10 meg ohms.



Time for a new antenna?



Thanks in advance,

Vin



Why do you suspect the antenna is shot?

Are you measuring at the end of 70 feet of coax
attached to the antenna or directly at the antenna
terminals?

Chuck

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News==----
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=----

"Vinny" wrote in
:

It's an old antenna, it was on the boat when I bought it. There's no
markings left on it but it has a blue and green pin stripe near the base
which I think is shakespeare (sp?)



If in doubt - Dump it and feel better....

What kind of boat is this on?.....

Sailboats should use Metz Manta 6...
http://www.metzcommunication.com/manta6.htm

The one I gave away with the Sea Rayder jetboat under it was on its third
fast boat. CG uses them on their boats, too.

NO FIBERGLASS for the UV to eat and fall apart.....

Guaranteed for LIFE.

"Larry" wrote in message
...
"Vinny" wrote in
:

It's an old antenna, it was on the boat when I bought it. There's no
markings left on it but it has a blue and green pin stripe near the base
which I think is shakespeare (sp?)



If in doubt - Dump it and feel better....

What kind of boat is this on?.....

Sailboats should use Metz Manta 6...
http://www.metzcommunication.com/manta6.htm

The one I gave away with the Sea Rayder jetboat under it was on its third
fast boat. CG uses them on their boats, too.

NO FIBERGLASS for the UV to eat and fall apart.....

Guaranteed for LIFE.


It's on a '95 seaswirl striper walk around. This is my 3rd year with the
boat and I'm almost certain the antenna is the orginal. I don't know how
long they typically last but 10 years of sun and salt seems like a long time
for
a low end antenna to last.
I'll do a few tests with the guys next to me in the marina. Even with no
antenna, they should pick up a signal from 10 feet away. That will
at least prove the radio probably works OK.

"Vinny" wrote in
:

10 years of sun and salt

Yes, dump it.....

Now, let's figure out which antenna you should get. The biggest antenna
isn't the one you need, or want....

Is this antenna mounted on a lay-over base or fixed mounted? If it has a
lay-over base, does it also have an extra mount to hold it up on the side
of the cabin, for instance? How much do you have to lay it down? As you
probably trailer it, laying over another monsterous 8' long antenna is
just another chore you probably don't need.

I'm looking at the 21' walkaround's picture on Striper's webpage. Nice
boat, by the way....(c;

Ok, what would you think of putting an antenna on top of the hardtop that
only sticks up 40", is stainless steel, not fragile plastic, mounted
through a 3/4" hole so there's no coax exposed to the weather? Is there
an overhead radio enclosure under the top? If so, we can use just a
jumper cable between the radio and the antenna, which has a standard SO-
239/U female coax connector sticking down into the cabin. NO coax
losses, nothing exposed to passengers, weather, corrosion....great, easy
install.

http://www.metzcommunication.com/manta6.htm

It won't split, crack, weather, produce fiberglass shards to cut your
hands after the gelcoat weathers off and you can move it from boat to
boat for years. It requires no ground or ground plane. You can hold it
in your hand and it will produce a great signal. Because its cable is
SEPARATE from the antenna, when the cable breaks, we replace the cable,
not the whole antenna, like a Shakespeare. How stupid to have coax
potted into a base....idiots.

Why not a monstrous 8db antenna? Pattern....radiation pattern.

The 1/2 wave little Manta's radiation pattern looks like a donut laying
on the table...the table being the sea surface. If you tilt the donut as
the boat rolls and pitches, a good part of the donut still points to the
spoon laying on the other end of the table, the target radio system
you're trying to talk to. Now, the bigshot, high gain antenna gets its
signal gain from flattening out the donut as if you drove the car over
it. All this gain is out the ends of a very flat radiation donut,
perpendicular to the antenna. If the antenna rolls to port, for
instance, the signal to port is pointing into the sea a short ways from
the antenna. The signal to starboard is pointing towards the sky.
Neither of those signals are going to the targets off the beams. If the
boat/antenna pitches, the signal isn't pointed at the targets off bow and
stern. The fat donut of the 1/2 wave antennas lets lots of signal hit
the target's antenna, even if it's pitched or rolled over 30 degrees.

My last little boat with this antenna in it was a Sea Rayder 16' jetboat.
The Manta was mounted to a plastic handle in the bow just inside the
gunwale and the top of it was about 4' off the water. Range on 25 watts
was about 20 miles in normal conditions....except, of course, if we were
jumping wakes...(c;

If you don't like it, simply return it to Metz. I bet you'll keep it.
You'll hardly remember it's there...going under a bridge, for instance.
If it hits anything, it will bend back horizontal and spring right back
to vertical.