Dear John,

Thank-you very much for your detailed reply.

Would the following kit be OK?
http://www.maplin.co.uk/Module.aspx?...61&crit eria=
(or
http://cgi.ebay.co.uk/RG-58-50-Ohm-C...QQcmdZViewItem)
http://www.maplin.co.uk/module.aspx?...&doy=14m3&QV=P
http://www.maplin.co.uk/module.aspx?...&doy=14m3&QV=P
http://www.maplin.co.uk/Search.aspx?...YW04E&DOY=14m3

I notice that the ariel has a "PL259 plug fitted" ("Right-Angled UHF
Plug"). This looks fairly similar to what is actually on my radio - can
I just ask if you are sure the F-15 has a BCN connector [I can't find
the technical specs that tell me what it is, and I don't know the
difference!]

BTW it was a local radio enthusiast that I asked (member of RAYNET) but
I failed to get his contact details (it was a 2 minute conversation, in
between us both having to run to an emergency!).

Many thanks for all your help,

Alex


John Kasupski wrote:
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/

On 14 Mar 2006 04:15:35 -0800, wrote:

Dear John,

Thank-you very much for your detailed reply.

Would the following kit be OK?
http://www.maplin.co.uk/Module.aspx?...61&crit eria=
(or
http://cgi.ebay.co.uk/RG-58-50-Ohm-C...QQcmdZViewItem)
http://www.maplin.co.uk/module.aspx?...&doy=14m3&QV=P
http://www.maplin.co.uk/module.aspx?...&doy=14m3&QV=P
http://www.maplin.co.uk/Search.aspx?...YW04E&DOY=14m3

That Maplin site apparently (and hopefully, for your sake!) works better in the
UK than it does here in the USA. I was only able to get one of the four pages
you linked to loaded from here - the first one, showing the RG-213 coaxial
cable. This would probably be okay for a *very* short run, a few feet at best.
I'd recommend thicker and less lossy cable for anything longer than that.

It's difficult to be very specific from a few thousand miles away, but in
general: The longer the coaxial cable is, the more loss of signal will occur
between the radio and the antenna (aerial). This is why I recommended getting in
touch with some local hams - they can show up at your site and see the actaul
situation you're dealing with, and then tell you exactly what you need to avoid
having excessive feedline loss. I can't do that from here. Different grades of
cable have different amounts of loss. That one lonk looks like it's to RG-58U,
so I'll use that as an example - RG-58U would be fine on HF. On VHF, it's almost
certainly going to be very lossy unless your antenna is ten feet from the radio.

I notice that the ariel has a "PL259 plug fitted" ("Right-Angled UHF
Plug"). This looks fairly similar to what is actually on my radio - can
I just ask if you are sure the F-15 has a BCN connector [I can't find
the technical specs that tell me what it is, and I don't know the
difference!]

This one I can answer. The PL259 (and the female SO239 that mates with it)
thread together, you insert the PL259 into the SO239 and then turn the outer
sleeve on the PL259 several turns to tighten it on. With BNC connectors, you
push it in and give it about half a turn, and it's on. I looked at a picture of
the F-15 and it appeared to me to be a BNC, but in any event, if you have to
screw the thing on there it's probably a PL259, if a half-turn locks it in place
it's probably a BNC.

BTW it was a local radio enthusiast that I asked (member of RAYNET) but
I failed to get his contact details (it was a 2 minute conversation, in
between us both having to run to an emergency!).

OK, RAYNET is comparable to ARES here in the US. You might wish to visit the
following web page, find a RAYNET team in your area, and contact them for some
hands (and eyes)-on assistance. Any ham looking at your situation first hand can
give you a much better estimation of what's best for your particular situation
than I could possibly give you from here. :-)

http://www.raynet-uk.net/main/contact.asp

Or http://www.raynet-uk.net/main/zones.asp

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/

Dear John,

Thank-you so much for your detailed reply.

The current areial is indeed a screw fit rather than twist which is
good news because it reduces the number of connectors!

Does the "military" grade version of the cable,
http://www.maplin.co.uk/module.aspx?...=14m3&QV=P#faq
work any better? I can't see if the only difference is that the outer
sheath is tougher or if this actually means that the cable is less
lossy. I reckon that its going to be a maximum of 20ft from handset to
the aerial.

I'll drop the RAYNET guys an email. Once again, many thanks for your
help. I'll certainly post here if I end up doing this with any advice
for anyone else that might find this post!

Many thanks,

Alex

Just noticed that Tom Hanratty (top of the list on the raynet zones.asp
file) was one of the guys I had a chat with over the w/end! How easy it
was to find his email address - thanks for sending me to that link!

Alex