I once retuned a 800 MHz TX/RX duplexer to 23cm by removing the tuning plunger and cutting off the outer fingers.
Then I used a fine hacksaw to cut new fingers and reinstalling the inner plunger.
Finally I recut all the interconnecting cables to the correct frequency.
I did not modify the loop on the small tuning device but there are places to learn about that.
Using a Rigol spectrum analyzer the pass and notch bands tuned perfectly.
The loss was 3 db or half the power.
Note: I have no real technical knowledge about this, just like to experiment and wasn’t afraid to ruin a cheap duplexer I brought off eBay if it didn’t work out.
Rex, AJ4GC
