Gary,
A return loss bridge (RLB) is an extremely useful tool for tuning the
pass function of a BpBr duplexer. That's because the bandpass response
of each cavity in a BpBr duplexer is very subtle- nothing like the peak
you will see in a bandpass-only cavity. Even when three BpBr cavities
are in series, the bandpass response is rather wide.
An RLB allows any good spectrum analyzer to emulate the reflection
capability of a vector network analyzer to a sufficient degree that
bandpass tuning can be much more precise. Instead of viewing the
transmission bump, you can view the reflection notch- which is very
sharp. With such a clear indication of the bandpass tuning, the cavity
can be tuned within a few kHz of the exact pass frequency.
It is essential that all interconnecting cables and connector cables be
of very high quality, and the spectrum analyzer's reference oscillator
be on frequency. It takes some practice to use an RLB correctly, but
it can allow you to tune a duplexer with remarkable precision.
73, Eric Lemmon WB6FLY
Quoting [EMAIL PROTECTED]:
>
> Gentlemen,
> Will be starting a new science project setting up Wacom 641 on 2 meters.
> Have a Rohde & Schwarz monitor receiver with S meter, DB pads, dummy loads
> etc. Plus an IFR 1500. But I see comments on a unit called a 'return loss
> bridge' for the IFR. How important is this return loss bridge and
> what is it's
> claim to fame? Do I really need one? Also have an old HP 8554B Spectrum
> Analyzer.
> Thanks,
> Gary K2UQ
>
>
>
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