[TrunkCom] outside antennas

Mon, 30 Dec 2002 19:18:55 GMT

Remember:  Antennae work the best when they are designed for a certain range especially if they are designed t oresonate at @ certain frequency.

I think that means if you use an antenna for 800 - 900; it might work the best @ around 850 Megacycles.

---------- "Todd Hartzel" <[email protected]> writes:

From: "Todd Hartzel" <[email protected]>
To: [email protected]
Subject: Re: [TrunkCom] outside antennas
Date: Mon, 30 Dec 2002 07:53:35 -0600

Greetings Jeff,

> On 29 Dec 2002 at 19:47, JEFFREY MICHAEL KENYON wrote:
>
> Hi everyone.  I am finally going to be putting up and outside antenna
> in the near future.  Although it will mainly be for ham use, I have
> always wanted something that will do well on 800 MHz for scanning
> distant trunked systems, and systems that I am just on the fringes of.
>  The ham bands that I will be using this for is 2-meters and 440, but
> I figure that if I am going to do something I had might as well look
> into what will help also with scanner use as well.  Any help would be
> good, and thanks and happy new year.

For 800/900Mhz, don't use anything long, or with gain.  Use something
that has unity gain (0db).  The reason ; I've done lots of traveling with
my various radios and such.  And the #1 reason for 800Mhz reception
problems using our scanners is'OVERLOAD'. Or desensing.  Its a 
widespread problem, that is *NOT* unique to St Louis, Mo.  Its 
everywhere.  Our scanners can't cope with the tremendous overload
of signals like:  High-Power 928-935Mhz Flex Pager signals, 870-
895Mhz Analog, CDMA & TDMA Cell signals & lastly the in-band
interferance from Nextel's iDEN network between 851-866Mhz.

I have found the very best apporach is to put an antenna out there
on the roof, but make it as low-gain as possible, and for a base
station, try to use a directional (beam) if possible.  'OVERLOAD'
is here to stay, there are ways we can reduce it.  The chreapest
approach is to start with unity-gain if it must be an *OMNI*.
If not, go for directional (beam).

I use my PRO-94, PRO-92 & BC-780xlt quite abit on the road.
I use nothing but a fleet of ultra-short antennas.  For my PRO-94
& PRO-92, I use -Stubby-duck- antennas.  Wanna see one:

http://www.n0vkg.web1000.com/stx800.htm

(This picture is kinda old.  It was shot inside St Louis City  
Police HQ.  Look at my bc-245xlt.  That is the Comet CH-32 
'Miracle Baby' stubby duck on the end of my 245xlt.  It is 
quite a wonder of  antenna for UHF (400Mhz), 800Mhz &
900Mhz.  It has no VHF performance. This antenna has 
single-handedly stopped a lot of the 'OVERLOAD' that I 
can experience in the Urbanized areas of St Louis, Mo.  
Especially downtown.   It really does great when on the 
PRO-92.  Oh my, in downtown, when I use the CH-32 with 
the PRO-92, 'OVERLOAD' disappears and does *NOT* 
show up at all.   In downtown St Louis, everything worth
listening to on any scanner is in the UHF & 800Mhz range.
Its a perfect urban scanner arrangement)  

I have 2 of those CH-32s.  Here is the another shot of the
CH-32 on my bc-245xlt:

http://www.n0vkg.web1000.com/stx800_2.htm

So with all of this in mind.  The roof is still the best place
for the outdoor antenna.  If it must be omni-directional,
go with unity-gain ( or 0 db-gain).  However, if possible, 
use a Beam,  instead.

This is my opinion.  Hope it helps alittle.  The alternative is
to employ Pass-band filters too, which would help to 
complimentany arrangement you choose.  If the Filters
were to be extremely effective, you could 'UP' the gain
of the 'OMNI' base antenna. 

Remember, our scanners are not built with IRON-CLAD
RF 'Front-Ends'.  This is the part that will dictate your
end-solution.  I wish you good luck on it.  If you have 
good success, please share it with us on Trunkcom.

73 from todd hartzel / n0vkg
http://www.n0vkg.web1000.com

_______________________________________________
TrunkCom mailing list
mailto:[email protected]
http://mailman.qth.net/mailman/listinfo/trunkcom

________________________________________________________________
Sign Up for Juno Platinum Internet Access Today
Only $9.95 per month!
Visit www.juno.com