No.
----- Original Message -----
From: "Mathew Quaife" <[EMAIL PROTECTED]>
To: <Repeater-Builder@yahoogroups.com>
Sent: Monday, July 26, 2004 10:17 PM
Subject: Re: [Repeater-Builder] Receiver Sensitivity Testing Through
Duplexer
> Could I get by using a seperate antenna to test for desense? Say leaving
> the antenna for the receiver through the duplexer and hooking the
> transmitter up to another antenna, would that work the same to test for
> desense. I tried to make an iso-tee, did not heave real good luck with
it,
> but then as far as a machinest, I have to luck at that, hihi....
>
> Mathew
>
> ----- Original Message -----
> From: "Eric Lemmon" <[EMAIL PROTECTED]>
> To: <Repeater-Builder@yahoogroups.com>
> Sent: Monday, July 26, 2004 6:09 PM
> Subject: Re: [Repeater-Builder] Receiver Sensitivity Testing Through
> Duplexer
>
>
> > Mathew,
> >
> > There may be more than one problem to consider. It is wise to check for
> > desense, but also be aware that some amateur-grade handhelds are
> > notorious for excessive PL deviation. Alincos are the worst, in my
> > opinion. My DJ-S11T had 1400 Hz of PL deviation out of the box, when
> > 400-700 Hz is ideal. When a commercial-grade repeater (MICOR, GE, etc.)
> > receives an input from a user with excessive PL deviation, the user's
> > voice may over-deviate the carrier, causing the PL to be clipped. When
> > this happens on a PL-required repeater, the repeater shuts down on voice
> > peaks. Of course, this symptom is made much worse when the voice
> > deviation is too high, as well. One way to check this is to use a
> > commercial-grade handheld radio to check for the same symptoms.
> >
> > To check for desense, you can use an "iso-tee" to inject a low-level
> > signal into the antenna feedline at the receiver frequency, while
> > monitoring the receiver audio at 12 dB SINAD with the repeater
> > disabled. Then enable the repeater so that the transmitter turns on.
> > The SINAD reading should drop no more than 1 dB. Some service monitors
> > will change modes when RF is detected, so you may want to use a separate
> > antenna, instead of the iso-tee, to get the test signal into the
> > receiver.
> >
> > If your repeater is at a site with other transmitters, you may need to
> > add some bandpass-only (NOT pass/notch) cavities between the duplexer
> > and the receiver input. As has been noted many times on this list, a
> > pass/notch or "BpBr" duplexer has almost no bandpass selectivity, and a
> > nearby transmitter many MHz away can easily cause desense in your
> > receiver if not filtered out with a dedicated bandpass cavity.
> >
> > 73, Eric Lemmon WB6FLY
> >
> > w9mwq wrote:
> > >
> > > I need a little advice here. I want to test my repeater's sensitivity
> through the duplexer, while the transmitter is keyed up, into my Cushman
> Service Monitor. What is the best method of doing this? Do I need an
> isolator of some sort, or will the service monitor handle both the
incoming
> power and the outgoing signal
> > > generator? It's a Cushman 6030 by the way. The repeater is working
> excellent for the most part. The problem that I am having is on weak
> signals, the audio is being chopped out, almost like the PL deck is
shutting
> down. On the bench, the receiver is at about .25 microvolts sensitivity
at
> 12 dB Sinad. Audio out of the transmitter
> > > is about 4 kHz wide, and clean at 100 watts. Any suggestions?
> Handhelds are able to get in from about 4 miles away, mobiles have no
> troubles at 30 miles away. The antenna is only up at 60' right now, fed
> with 120' of 7/8" Andrews hardline. But it seems the handhelds are the
ones
> having the problems, and their signal is not really that bad. Help
please.
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
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