Lou, I doubt that you can use this band-reject (notch) duplexer at 70 cm without factory rework. The coupling loops were designed and positioned specifically for the 450-512 MHz band, and they are not externally adjustable. The lengths of the jumper cables are unique to the band for which the duplexer was originally tuned, and are not appropriate for any other band. That duplexer has a specified rejection of 45 dB minimum, which may be insufficient for your application. Look at GE LBI-3971 for information on this duplexer.
A few years ago, I ordered a Celwave mobile notch duplexer for a 70 cm repeater, and I was astounded by its outstanding performance. The difference in performance between this duplexer that was ordered from the factory for Ham-band use, and one that was (supposedly) retuned from a commercial (453-458 MHz) pair, was remarkable. You can probably buy a new notch duplexer made for your 70 cm pair for very little more than it would cost to rework an existing unit. Moreover, there is much more to changing the band coverage than simply turning the tuning screws; it needs to be remanufactured for 70 cm. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Lou Sent: Tuesday, February 10, 2009 5:04 PM To: [email protected] Subject: [Repeater-Builder] Duplexer Information Needed I am looking for information on the following Duplexer: Decibel Products TR Duplexer. GE Part No. 19D402955-P10. Serial No. D 50171-9. Freq Band 450 to 512 MHz. Freq. Separation: 3 to 20MHz. We would like to use this in the 70cm ham band. What is need to make it work? Is there a source of information on tuning these, type of equipment needed etc? Thanks, Lou K2LRV
