Filter hacking for 2395 ISS TV

[G3GJA]

Yes it will change the tuning Gareth.

I used PTFE tubing placed over the tuning pistons to lower the operating frequency of a 10-cavity duplexer originally intended for use at 1496MHz and 1354MHz so that I could tune it to 1308MHz and 1275MHz for use in a repeater.

Although the the 33MHz separation was much less than the original 142MHz, it still gave useful isolation between the TX and RX ports. However, it didn't cope with the power level needed and was prone to flashing over, but it now has use as a look-through filter at home so I can monitor the repeater whilst transmitting.

Clive

[radiogareth]

As there was a piece of PTFE in the workshop I cut off a 25mm wide strip (1.25mm thick) and placed it between the tuning screws of the 10MHz filter.
Pictures show the effect - no attempt made at retuning as it was fine as it was for RX of the ISS.
Gareth

No_tune_with_PTFE.jpg (159.13 KiB) Viewed 14 times

No_PTFE.jpg (161.28 KiB) Viewed 14 times