[AReU] Interdigital Filters

[Tony Stone]

Hi Tom,

Do you remember those two filters I picked up at your house the other month?
They were for the 1.9 GHz PCS band.

I had tested the smaller one for use at 1.3 GHz and determined that it would
not go down that far but was optimistic about making them work at 2.3 to
2.4 GHz.

I have been working on them this weekend and I am proud to report that I
have the smaller (three element) filter working fine on 2.3 to 2.45 GHz.
That covers the 13 cm. weak signal calling frequency and the AO40 "S"
band downlink frequency. I removed the small resonator with the male
SMA connector on one end of the filter and replaced it with a female
"N" connector and cut the filter elements to 78% of their original length.
It tuned up on the first try!!!!!!!

The larger filter was a different and somewhat laborious experience. I
figured
that the 5 elements would be too sharp to be of any use so I proceeded to
cut the rectangular piece down to the same size as the smaller three element
filter. I removed the small resonator, added the female "N" connector and
shortened the tuning rods as in the smaller filter. It tuned up on the first
try also!!!!!

I will bring the filters to AREU next Tuesday and will hope to see you
there.

I have an idea for a pair of low power 13 cm transceiver that will use these
filters and a couple of harmonic mixers that I have. All that will be
required
is a local oscillator at some sub multiple of 2.304 GHz minus the 144 MHz
intermediate frequency and a low power two meter transceiver.

73

Tony