Showing posts from March, 2018

2m Duplexer unusual design repair tune pager-reject

2m Duplexer design repair tune pager-reject Introduction My local radio club's main 2m duplexer had an intermittent fault. The duplexer was fixed and retuned to a new channel, 1600, not 600 kHz split, partly to move the RX further from a Pager TX.

The Telewave TPRD-1556 Pass-Reject duplexer has an unusual coupler that I had not seen before that works very well, 45 db reject each. They should be possible to DIY. The fault was a defective piston capacitor used to tune a cavity.

An unexpected benefit of the pass-reject RX cavities is a significant 72 db reject of the 148 MHz pager TX. More is possible, if needed from notch cavities at 25 db reject each.

Tuning high performance cavities, 45 db each, highlights the limitations in instrumentation, particularly the dynamic range, 85 db, with the reject response lost in the noise floor.
Design of the Telewave TPRD-1556 Pass-Reject duplexer  The Telewave TPRD-1556 Pass-Reject duplexer looks like any other six cavity pass-reject duplexer, …