[amsat-bb] Re: Eliminating Desensing

[David Donaldson]

The quality of the devices and the design of the amp is significant.  In
the cellular world at 850 I have seen cheap poorly designed  (talking
thousands for these units) TTA's generate more crud from minimial
colocated signals then the well designed cheap ones.  All the units I
now use have a high IP3 point with integrated filters or duplexers.  The
unit ADC Telecom used to make had the filter integrated in the housing
(machined out of a solid aluminum block).  I was able to use these in
downtown settings without fear of intermod.  Newer units work as well
but now have a seperate filter from the housing.
Moral of the story: It's design not price that is the key.  Cheaper not
always badder. Compare specs.
Other suggestion would be to establish the power level where the
interference begins. Though it is not linear it will give u a sense of
the degree of interaction between the UL and DL antennas.  Intermod and
desense always has a bit of magic to it thanks to its none linear
behaivor

Hope this helps someone
Dave D
WB7DRU

Sent with Wireless Sync from Verizon Wireless

Another option is to use a preamp with good filtering on the input. I
had issues with Mode J desense with my Icom AG-35 preamp, but have none
now that I have switched to SSB Electronics preamps.

As always, Your Mileage May Vary (YMMV).

73, Drew KO4MA





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