Send it into TX RX they will tune it at a very reasonable cost and get it
back to you in a week or so.
----- Original Message -----
From: "Eric Lemmon" <[EMAIL PROTECTED]>
To: <Repeater-Builder@yahoogroups.com>
Sent: Sunday, March 14, 2004 3:40 PM
Subject: Re: [Repeater-Builder] TX-RX Duplexer Tuning
> Tim,
>
> Yes, you can rent a spectrum analyzer- preferably with a return-loss
> bridge, or you can borrow one.
>
> Seriously, though, the duplexer is such a critical component in a
> repeater system that you really should not try to cut corners on its
> tuning. Once upon a time, I personally used some "creative" means to
> tune duplexers, before I decided to acquire the proper test equipment,
> and I always was able to improve on my prior work, using the proper test
> equipment.
>
> A spectrum analyzer with a tracking generator is the minimum essential
> tool for tuning duplexers. However, not all spectrum analyzers are
> accurate enough for such work, and fewer still have enough dynamic
> range. Most low-end spectrum analyzers have an 80 dB dynamic range,
> which is insufficient for duplexers that might have greater than 100 dB
> of isolation. That's where a network analyzer really shines.
>
> A return-loss bridge is an important accessory for a spectrum analyzer
> (it's built-in to a network analyzer), since it allows you to tune for
> an extremely sharp peak (actually, it's a sharp null) when tuning the
> bandpass element, thus squeezing the nth degree of performance out of a
> duplexer. A properly tuned duplexer should NEVER need to be tweaked at
> the transmitter site. If tweaking a duplexer at the site does improve
> either the reception or the power output, the chances are good that the
> spectrum analyzer used to tune it is off frequency. It's also possible
> that there is a significant impedance mismatch, but I don't want to beat
> that dead horse!
>
> I prefer to use a network analyzer to tune duplexers, because I can
> easily verify that the jumper cables between cavities are the correct
> length. In the case of your TX-RX duplexer, you probably should give
> the factory a call to confirm the cable lengths for the model and
> operating frequency. Depending upon your location, it may be
> cost-effective to ship the duplexer to TX-RX, or to another vendor such
> as EMR, for professional conversion and tuning to your repeater pair.
> If you do this, do not let anyone touch the tuning controls after its
> return!
>
> The Bottom Line: Yes, you can tune a duplexer without any fancy
> equipment- but why would you want to, if your objective is to have a
> first-class repeater?
>
> 73, Eric Lemmon WB6FLY
>
> timtarhanick wrote:
> >
> > I have a TXRX duplexer I am going to use on two meters. Everything I
read, including the manual from TXRX states I need a spectrum analyzer for
the tuning the duplexer. Is there any other way besides buying a spectrum
analyzer to do the job?
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
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