I have had an antenna I bought from RS years ago. I bought it for a Pro-79.
I some times had trouble picking up the County calls where I work. The new
one is several inches longer, and "claimed" to be great for this. It turned
out it did nothing, and got relegated to the junk drawer. Well now that the
city is switching over to an 800 trunked system I went to a 95 I had bought
a couple years ago. The antenna can be a pain at times when carrying the
thing so I decided to see if shortening it would hurt anything on the 800
band. I noticed for years now GMRS radios come with very short antenna's and
work great. So anyway I started lopping off an inch at a time, and now it's
down to 4 inches, much easier to carry, and I can't tell any difference in
either the 800 or the 400 band reception. I know nothing about how this
works. Is the longer antenna supposed to work better with other bands or
something? I would like to lop off a little more if it has no ill effect. I
guess I will see if I can pick up an old scanner that does not work on E-bay
that has a BNC connector to play with and see just how short I can go.
Anyway what's the point in the longer antenna?
Thanks

On Tue, 26 Oct 2004 18:25:35 GMT, "Alex Clayton"
wrote:

[snip]

works. Is the longer antenna supposed to work better with other bands or
something? I would like to lop off a little more if it has no ill effect. I

The longer the antenna, the lower the frequency.

There are many resources out there that will show you how to use an
SWR to tune your antenna to the proper frequency, for stuff around
850MHz, 3.3 inches is the resonant length for 1/4 wavelength.. a
little bit shorter to account for the velocity in the material.

Be careful, get a good SWR if you can and use that. If not, I'd move
down to 1/8 to 1/4 inch snips at a time, not a full inch. As soon as
it starts to get worse, stop cutting, because you're at the low end of
the length.

Going below 1/4 wavelength you can't get any shorter and have it get
better. If you were going for 1/2 (6.6 inches @ 850mhz) and cut too
far, you could "start over" and keep cutting it down to 1/4, but
you're well past that if you're down to 4" already.

"asym" wrote in message
news
On Tue, 26 Oct 2004 18:25:35 GMT, "Alex Clayton"
wrote:

[snip]

works. Is the longer antenna supposed to work better with other bands or
something? I would like to lop off a little more if it has no ill effect.
I

The longer the antenna, the lower the frequency.

There are many resources out there that will show you how to use an
SWR to tune your antenna to the proper frequency, for stuff around
850MHz, 3.3 inches is the resonant length for 1/4 wavelength.. a
little bit shorter to account for the velocity in the material.

Be careful, get a good SWR if you can and use that. If not, I'd move
down to 1/8 to 1/4 inch snips at a time, not a full inch. As soon as
it starts to get worse, stop cutting, because you're at the low end of
the length.

Going below 1/4 wavelength you can't get any shorter and have it get
better. If you were going for 1/2 (6.6 inches @ 850mhz) and cut too
far, you could "start over" and keep cutting it down to 1/4, but
you're well past that if you're down to 4" already.


How much do they cost? Looking over e-bay it looks like there is no shortage
of replacement antennas if I screw one up. If I buy an SWR (what the hell is
this?) I don't know what I would do with it after? I took another inch off
it, and it still works great for the 800 and 400. The police here are
switching over to the new 800 trunked system so they are broadcasting on
both the old 450's and new at the same time. Switching back and forth
between the two reception is still as far as I can tell, the same as it was.
The county and State Patrol here use 150's. I normally don't bother with
them but to test it I turned them on and they are working fine with the 3
inches too. Wish I had known this long ago it would have been nice not to
have the longer antenna getting in the damn way.

a swr meter will do nothing for you, you need to transmitt in order for it
to work. you would need an antenna analyser and for the $100 bucks you
would pay for it, would not probaly be worth your money. as you say ants
are cheap on ebay.


"Alex Clayton" wrote in message
nk.net...
"asym" wrote in message
news
On Tue, 26 Oct 2004 18:25:35 GMT, "Alex Clayton"
wrote:

[snip]

works. Is the longer antenna supposed to work better with other bands or
something? I would like to lop off a little more if it has no ill
effect.
I

The longer the antenna, the lower the frequency.

There are many resources out there that will show you how to use an
SWR to tune your antenna to the proper frequency, for stuff around
850MHz, 3.3 inches is the resonant length for 1/4 wavelength.. a
little bit shorter to account for the velocity in the material.

Be careful, get a good SWR if you can and use that. If not, I'd move
down to 1/8 to 1/4 inch snips at a time, not a full inch. As soon as
it starts to get worse, stop cutting, because you're at the low end of
the length.

Going below 1/4 wavelength you can't get any shorter and have it get
better. If you were going for 1/2 (6.6 inches @ 850mhz) and cut too
far, you could "start over" and keep cutting it down to 1/4, but
you're well past that if you're down to 4" already.


How much do they cost? Looking over e-bay it looks like there is no
shortage
of replacement antennas if I screw one up. If I buy an SWR (what the hell
is
this?) I don't know what I would do with it after? I took another inch off
it, and it still works great for the 800 and 400. The police here are
switching over to the new 800 trunked system so they are broadcasting on
both the old 450's and new at the same time. Switching back and forth
between the two reception is still as far as I can tell, the same as it
was.
The county and State Patrol here use 150's. I normally don't bother with
them but to test it I turned them on and they are working fine with the 3
inches too. Wish I had known this long ago it would have been nice not to
have the longer antenna getting in the damn way.

On Tue, 26 Oct 2004 21:25:08 GMT, "Alex Clayton"
said in rec.radio.scanner:

How much do they cost? Looking over e-bay it looks like there is no shortage
of replacement antennas if I screw one up. If I buy an SWR (what the hell is
this?)

An SWR (Standing Wave Ratio) meter - you need a signal source, like a
transmitter, to feed it.

An antenna noise bridge, a signal source like a signal generator, and
a few weeks of study will work better if you don't have transmitters
available for the frequencies in question.

Or you could just by a "stubby" antenna. They work worse than
standard length antennas, but since rubber ducks work so poorly to
begin with, you aren't losing much.

"Al Klein" wrote in message
...
On Tue, 26 Oct 2004 21:25:08 GMT, "Alex Clayton"
said in rec.radio.scanner:

How much do they cost? Looking over e-bay it looks like there is no
shortage
of replacement antennas if I screw one up. If I buy an SWR (what the hell
is
this?)

An SWR (Standing Wave Ratio) meter - you need a signal source, like a
transmitter, to feed it.

An antenna noise bridge, a signal source like a signal generator, and
a few weeks of study will work better if you don't have transmitters
available for the frequencies in question.

Or you could just by a "stubby" antenna. They work worse than
standard length antennas, but since rubber ducks work so poorly to
begin with, you aren't losing much.

Well I got a lot of responses to this and I still don't know any more than I
did. I took another inch off, the 150's (county police), 450's & 800's (city
police) still come in great. So bottom line now I can carry the thing at
work much easier and it works great. I still have the original antenna if I
ever need it, but I have never cared about the HAM, Aircraft and such.
If anyone else has wished the antenna could be shorter to not be in the
way I would recommend getting a spare first before trying this. Lot's of
them around.