Jerry:
You might first wish to measure the reverse isolation of a MMIC before
you make that statement. While they are great devices, isolation is not
their strong suit.
The Gali74, which I use for a variety of purposes, has an isolation of
around 28 dB at the K2's IF frequency. The gain is 25 dB, so if you pad
the output for unity gain, you are around 53 dB. With a Softrock's
typical -40 dBm LO leakage, that strikes me a bit on the marginal side.
Jack K8ZOA
Jerry Flanders wrote:
I assume a simple MMIC amp plus a simple resistive attenuator circuit
will provide enough isolation and also provide for matching levels
up/down as may be necessary. At least, that will be my first cut at
the problem unless somebody else comes up with a better plan before my
K3 arrives.
At down east microwave (
http://www.downeastmicrowave.com/cat-frame.htm ),
see the
<http://literature.agilent.com/litweb/pdf/5967-6159E.pdf>INA10386
(DC-2GHz, 24dBG, 3.5dB NF +14dbm 1dB Gain compression ) for only $5.
Very easy to use something like this, I think.
Depending on the signal level of the K3 IF output, we might get enough
isolation from a resistive attenuator alone and still have a usable
signal level on the softrock panadaptor.
I would much prefer a plug and play manufactured solution if it takes
more than an attenuator, but not an expensive one.
Jerry W4UK
At 07:29 PM 2/11/2008, stephen pearce wrote:
A month or so ago one of the Elecraft engineers pointed out that
if the softrock lite rx is connected directly to the if port on the k3
there was a significant issue with coupling of rf from the softrock
board into the
rx if of the k# with consequent degradation in rx performance ...
Has anyone produced a design for a suitable isolation amplifier/
coupling stage which will
prevent this and still allow the softrock to be used (in conjunction
with a pc) as a panadapter?
Thanks
--
Stephen Pearce
zl1any
Whangarei
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