Re: [Repeater-Builder] Duplexer tuning with Return Loss Bridge

[Doug Zastrow]

Eric & the Group...   From discussion of vector network analyzers / return loss bridges on the list it certainly appears that this is the gold-standard for duplexer alignment.  Can anyone provide link(s) to a comprehensive tutorial on the subject?   Sometimes old dogs like me have to work a bit to learn new tricks but that doesn't stop me from trying!   While I have everyone...  I'd like to thank all of the list contributors who share their knowledge for the good of everyone.  It is truly appreciated.   A Joyous Holiday Season to all!     Doug ----- Original Message ----- From: Eric Lemmon To: Repeater-Builder@yahoogroups.com Sent: Wednesday, December 21, 2005 9:42 AM Subject: Re: [Repeater-Builder] Duplexer tuning with Return Loss Bridge 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 YAHOO! GROUPS LINKS  Visit your group "Repeater-Builder" on the web.    To unsubscribe from this group, send an email to:  [EMAIL PROTECTED]    Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.