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RE: Connecting ULNA to TranSystem dipole



Joe KA0YOS wrote:

	Are you going to disable the preamp in the TranSystem? (after adding
a DEM ULNA)

Wayne replies:

I wasn't planning to disable the preamp, because I presently only get a
S-zero signal level at 123 MHz from my TSI downconverter, even after cutting
the stub.  I don't know if that indicates that something is wrong with my
downconverter or what.  It's partly because my 2 foot dish has less gain
than what most people are using.

After learning that the DEM ULNA doesn't have useful bandpass filtering, and
that the physical connection to my dipole feed will be difficult/risky, I'm
planning to cancel my order for the ULNA and instead ordering the larger
TranSystem dish.  It would cost much less than the preamp and the physical
installation would be much easier than figuring out a way to get the ULNA
between the feed and the downconverter.

Joe, thanks for the encouraging report that you hear "just fine" with an
unmodified TranSystem converter.  I suppose you use a 3 foot dish?  Did you
change the crystal (which may give you a bit of image rejection)?  To get
better performance, I would like to add an ISM ceramic filter before the
mixer to filter out the 2155 MHz image signal.  I wish it was easier to get
our hands on those filters!

I wonder if an easy path to solve the image problem would be to change the
crystal in the TranSystem converter to make the IF frequency somewhere near
the upper limit of the VHF receiving range of the new satellite radios.
With a 170 MHz IF (2231 MHz L.O.), the image frequency would go down to 2061
MHz, which would be attenuates some by the stock bandpass filter.  A few
weeks ago there was a discussion of the frequency range of the PLL in the
TranSystem converter.  What was the conclusion about how far the PLL
frequency could be pulled without requiring component value changes?

Wayne Estes W9AE
Mundelein, IL, USA
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