Santiago Flatpack Duplexer at Otay

Last Friday 11/26/10, John K6XI, went up to Otay and did another duplexer swap out.
He installed a new duplexer and removed the original duplexer that talks to Santiago via our 420 link.
Today I met up with John at Elsinore Peak to get the original Santiago link duplexer that he removed.
A special thanks to John K6XI for all the help and time he has given in making several trips to the Otay 
repeater site for various swap outs of duplexers and killing the earwigs at the site.
Tonight I had a chance to take a look at the insertion loss on the receive port of the duplexer with the IFR.
This duplexer measured about 12 dB of insertion loss on the receive port.
It also appeared that the duplexer was out of tune on the tracking generator,
but this was caused by the earwigs and dirt inside the duplexer cavities.


Test setup photo showing the duplexer mounted in a vertical position
to duplicate the placement in the rack at the Otay repeater site



IFR Generator set at -80 dB. The analyzer display set at .2 megs.
The RX port on the duplexer showing -92dB on the tracking display.
Not good! That's about 12 dB or loss through this duplexer!



Moving the analyzer display to 2 megs.
Notice the bump going up? On a normally tuned duplexer you should see a valley.
It appears that the duplexer is not tuned right.
Even though the duplexer is tuned right, the earwigs in the cavities
caused the duplexer to appear to not be tune properly.



Opening the duplexer up reveals more earwig bugs.
The transmit side is on the left and the receive side on the right.



Taking a closer look to the left which is the receive side, it looks like dirt.



One last look before cleaning the duplexer and putting it back together.



IFR Generator set at -80 dB. The analyzer display set at .2 megs.
The RX port on the duplexer is now showing slightly less than -80dB on the tracking display.
The duplexer is now functioning normally with less than 1 dB of loss without being re-tuned.
Everyone is happy. <GRIN>


Lessons Learned

1) Bugs can screw up the insertion loss, especially on the receive port of a duplexer.

2) Bugs and dirt in the cavities of duplexers can also make the cavities go out of proper tuning.

3) When using these Celwave flatpack duplexers take the time to cover the holes so bugs can not climb in the cavities!