RadioBanter - View Single Post - Extending the range of VHF handhelds by using external ariels

March 13th 06, 07:25 PM posted to rec.radio.scanner

On 13 Mar 2006 10:30:27 -0800, wrote:

Hi Everyone,

I am a non-advanced user of licensed commercial VHF handhelds for a
large national charity.

We have a need to communicate between two sites. For various reasons
that I can't easilly explain in text I need to be able to put an ariel
on the roof and connect it to the handset in the building (there is a
large grass bank outside both buildings, but the roof -- roof is line
of sight and works well.

I spoke to someone over the weekend who told me that it was easy to do
- all I need apparantly is an ariel (identical to the ones that people
have on their cars), cut to the appropriate length for my frequencies
and then some standard TV cable to connect the ariel to my handheld.

Naturally, I have some questions
1) Where do I get adapters to plug one end of my TV cable into my IKOM
F-15 ariel socket?
2) Where do I buy the ariel? How do I calcualte the length that I
should cut it down to?
3) What sort of end do I need on the other end of my TV cable to plug
that into the ariel, or is this a solder job?

If anyone can help me with any of these or if you have any advice or
suggestions they would be greatly appreciated!

Many thanks,

Alex Davies

Alex, the Icom F-15 appears to use the standard BNC connector to mount the
factory-supplied "rubber duck" antenna to the radio.

The appropriate BNC connectors to use for connecting coaxial cable to one of
these radios for the purpose of connecting it to an external antenna are widely
available. They can be purchased at any RadioShack store.

You do NOT want to use TV cable to connect the radio to the antenna, as TV cable
has a 75-ohm impedance and these radios work at 50 ohm impedance. What you want
to use instead is a good quality 50-ohm coaxial cable such as RG-213, LMR400, or
Belden 9913. These can usually be purchased directly from manufacturers and
radio dealers.

As far as the antennas themselves are concerned, some technical knowledge is
needed to select, assemble, and tune a communications antenna for best
performance. Test equipment such as an antenna analyzer or, at the very least,
an SWR bridge is needed to properly do the job. This can be handled by any local
commercial firm that deals with communications equipment (the dealer where you
purchased the Icom F-15 radios might be a good starting point). Alternatively,
since you are a charitable orhanization, you might wish to seek assistance from
a local Amateur Radio (ham radio) club or emergency communications group such as
the ARES/RACES in your area. Ham operators frequently donate their time and
knowledge to assist charitable organizations with their events, and they have
the necessary expertise and equipment and experience to easily accomplish what
you want to do.

In short, what you want to do *is* easy - for someone who knows what they're
doing. However, for someone with no technical experience in setting up antennas,
it isn't as easy as it might initially seem. Do some looking around in your area
and get some hands-on help from some local hams, that would be your best bet.
They're smart enough to know how to avoid the pitfalls that go along with a
project of this nature.

Hope this helps,
John Kasupski, Tonawanda, New York
Amateur Radio (KC2HMZ), SWL/Scanner Monitoring (KNY2VS)
zIRC #monitor Admin
http://www.wzrd.com/~kc2hmz/
http://www.qsl.net/kc2fng/