: [Repeater-Builder] Diplex antenna installation using
coaxial cable for 10M and 6 M
At 05:32 PM 09/11/09, Joe, K1ike wrote:
The average coax cable of 1985 vintage probably had a velocity factor of
66%. If you didn't figure this into your calculations the coax would
appear to be about 1/4 physical
Being an analytical guy I modeled the antenna system in both
Ansoft Designer and an antenna modeling program. In Ansoft
Designer the antennas were modeled as a series RLC load with
50 ohms at resonance and a Q of 15. Transmission lines were
modeled with VF equal to that of RG-58A/U coax.
Steve,
The document in question is on the repeater-builder WEB site, not the files
area for this group.
There were two documents produced by Motorola , each dealing with specific
antenna combinations allowing the use of 2 antennas to cover areas of VHF
lowband. One dealt with using two
Milt said:
The
chart in the document was developed specifically for the
Spectrum series
series fed LB antenna. THE MEASUREMENTS IN THE CHART WILL NOT
WORK WITH
SHUNT FED COILS!
So as I guessed, the secret sauce is the type of antenna/loading coil used.
It might be a worthwhile
On Fri, 11 Sep 2009, Mike Morris WA6ILQ wrote:
I've been thinking about setting one up, as a future project is to set
up a mobile, either a low band Syntor-X9000 or a Maratrac, with some
channels on Red Cross and the rest on amateur 6m. I may have to go to
a screwdriver antenna as a 1mhz
Steve,
The shorter length stub most likely will give you wider matching
bandwidth... This may be why Motorola spec'd a 1/4λ stub as opposed to a
1/2λ stub, as well as nominally lower costs for the shorter cable length.
Maybe this will help explain my reasoning:
I did this same thing but went about it by a different direction.
I mounted the 52 mhz antenna and the 29 mhz antenna on the roof of
my Ford Explorer. I ran the coaxes down and connected them both to a
Comet 10meter/6meter diplexer and plugged the common end of the diplexer
into my radio.
Look
Thanks Mark and John for your response.
I can appreciate using the Comet CF-360B duplexer as a quick solution,
John. Thanks.
Mark, I can also see the matching bandwidth being better with shorter
transmission line.
But my concern is that 1/4 wavelength transmission line sections seem to
be very
--- On Fri, 9/11/09, Steven Schultz steven.schult...@gmail.com wrote:
From: Steven Schultz steven.schult...@gmail.com
Subject: Re: [Repeater-Builder] Diplex antenna installation using coaxial cable
for 10M and 6 M
To: Repeater-Builder@yahoogroups.com
Date: Friday, September 11, 2009, 5:29 PM
The average coax cable of 1985 vintage probably had a velocity factor of
66%. If you didn't figure this into your calculations the coax would
appear to be about 1/4 physical length, but would be an electrical 1/2
wavelength. Did you use a velocity factor in your calculations?
Would it be
It is on the repeater builder website already.
-- Original Message --
Received: Fri, 11 Sep 2009 05:32:31 PM PDT
From: Joe k1ike_m...@snet.net
SNIP
Would it be possible to scan the Motorola document that you have and
post it to the group? I've heard of it but I've never seen it.
I did take into account the velocity factor in the simulations.
In Ansoft Designer I can specify physical length and VF.
In the antenna simulator I am currently using I cannot specify the VF so VF
= 1 and
I use coax lengths equal to free space wavelengths.
The document was given to me in PDF
At 05:32 PM 09/11/09, Joe, K1ike wrote:
The average coax cable of 1985 vintage probably had a velocity factor of
66%. If you didn't figure this into your calculations the coax would
appear to be about 1/4 physical length, but would be an electrical 1/2
wavelength. Did you use a velocity factor
Mike-
How about using an automatic antenna tuner with a whip 6 foot whip?
-- Original Message --
Received: Fri, 11 Sep 2009 10:50:49 PM PDT
From: Mike Morris WA6ILQ wa6...@gmail.com
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Diplex antenna installation using
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