Note: forwarded message attached.
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--- Begin Message ---
Coy,
I have 2 each 929 and 940 Mhz paging transmitters at
my site. The 940 mhz transmitter is the Motorola. The
929 mhz transmitter is a Quintron.
My co-located 145.410, 2 mtr repeater works fine. I
use a TXRX duplexer. I use 40 ft of vertical
separation between the 900 mhz transmitter antennas
and the 2 mtr antenna. I understand what you are
talking about.
My repeater was there before the 900 mhz transmitters.
Yes, the noise floor came up when the 900 mhz
transmitters were added.
You state in your reply that you have a Wacom WP641
BpBr duplexer with an Additional Band Pass cavity
tuned to your receive frequency, a Notch filter, a 5
pole Helical front end feeding a MASTRII receiver with
additional 5 poles Helical filtration.
Can you tell us what frequency the notch filter is
tuned to?
Tell us about your band pass cavity. Is it a large
type like the DB4002 or is it a much smaller type.
Did you put the 5 pole helical front end filter in
front of your receiver to try to eliminate the 900 mhz
transmitter interferrence?
If you do have on frequency interferrence on 144.510,
then this will not help.
If I read your response correctly, your antenna coax
connects to your Wacom WP641 Duplexer, then through a
band pass cavity, then you have a notch cavity in
line, then the signal goes through a 5 pole helical
filter, and then possibly through another 5 pole
helical filter and then to your receiver.
You say that you are feeding a "MastrII receiver with
additional 5 poles Helical filtration." Are you just
commenting on the Mastr II front end casting filter or
do you actually have another 5 poles of Helical
filtering before the receiver? Were all these filters
installed to try to reduce the interferrence from the
900 mhz transmitter? Can you tell us your thought
process why they were installed?
You also say that "It's difficult to get 40 feet
vertical seperation on top of a building."
I do not know your situation, but over the years, I
have installed numerous 40 and 50 Ft Rohn 25G and Rohn
45G type towers on the top of buildings. I agree it
can be difficult but it can also be possible. Have you
asked if you can put up a few tower sections on the
roof of this building?
You may first want to try a push up mast with you
antenna on it to see if the interferrence goes away
with some vertical separation. These masts can be
found at any Radio Shack or TV stores.
Also, Spectrum Analyzers can be overloaded very easily
from nearby transmitters. You will need to use a
bandpass cavity in front of the Spectrum Analyzer
tuned to your receiver frequency to verify on
frequency interferrence.
John Lloyd, K7JL
Intermountain Intertie
http://www.ussc.com/~uvhfs/snowlink.html
Message: 10
Date: Tue, 10 Aug 2004 23:51:05 -0000
From: "Coy Hilton" <[EMAIL PROTECTED]>
Subject: Re: Motorola Nucleus II 900 mhz
AS stated in one of my posts, it's 144.510 MHZ. the
remainder of the
equipment used to assist with eliminating this problem
is as
follows. a Wacom WP641 duplexer, BpBr With an
Additional BAnd Pass
cavity tuned to my receive frequency, also a Notch
filter, a 5 pole
Helical front end feeding a MASTRII receiver with
additional 5 poles
Helical filtration. Please read the following
carefully and slowly.
THE INTERFERANCE IS ON THE RECEIVER FREQUENCY...I CAN
SEE IT ON THE
SPECTRUM ANALYZER and AT LEAST ONE OTHER PLACE ON THE
BAND AT
154.490, BROAD BAND, AND 20 KHZ WIDE.
This problem has to be solved at the source not band
aided by me
trying to put every kind of filter known to man on my
receiver. The
only way that I can solve it, is to move to another
site or turn my
receiver off. What I need to know is has anyone had
this problem
with this Transmitter and a little about the
transmitter like normal
configuration.
Oh, Motorola told me that They didn't build this model
transmitter. " It was built by Nucleus Inc a third
party company in
Texas"
It's difficult to get 40 feet vertical seperation on
top of a
building.
73
AC0Y
--- In [email protected], Mr John Lloyd
<[EMAIL PROTECTED]>
wrote:
> Coy,
>
> You did not say anything about what receiver
frequency
> you are using that is getting hit by the 900 mhz
> transmitter. Do you have a bandpass cavity on your
> receiver? If you are using a BpBr type of duplexer,
> then it has almost no rejection to the 900 Mhz
signal.
> You will need a bandpass cavity on your receiver.
>
> Most 900 Mhz paging transmitters have an output
power
> of 300-500 watts. You will need vertical separation
> between your antennas and bandpass cavities to solve
> this.
>
> The 25 Ft separation is next to nothing if it is
> horizontal. You will need at least 40 Ft of vertical
> separation between your antennas.
>
> John, K7JL
>
>
>
> Message: 9
> Date: Mon, 09 Aug 2004 22:15:52 -0000
> From: "Coy Hilton" <[EMAIL PROTECTED]>
> Subject: Motorola Nucleus II 900 mhz
>
> Does any one have any info on the possible problems
> with noisy
> Motorola Nucleus II 900 mhz transmitters? A paging
> company coo-
> locatde at the site with my repeater has one that's
> driving me up
> the wall. I have been working with them for 3 months
> now, to get it
> fixed. They recently changed antennas to one located
> about 25 feet
> away but there are spurs on my input frequency but,
> that did a lot
> of good. NOT. I'm about ready to fax Riley H. at the
> FCC. I'm trying
> to be a good neighbor but I've about had it
> 73
> AC0Y
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