RadioBanter - View Single Post

[email protected] · January 19th 07, 12:16 PM posted to rec.radio.shortwave

wrote:

Hi,

I would recommend reading the diversity section of "Communications
Receivers: DPS, Software Radios, and Design, 3rd Edition" by Ulrich
Rohde, Jerry Whitaker.

Generally speaking, mixing the inputs is helpful but not as good as
actively switching in the stronger signal.

This is somewhat more complex unless you have two receivers.

The 2 receivers part is not an issue. The one thing I have more then
enough of
is receivers. To do this right I will have to tap the AGC off both
receivers, feed
a comparator and use the comparator to select the strongest signal.

This was basicly an attempt to follow up on some comments by D Peter
Maus
about a "simple" diversity setup he had once that used multiple
antennas feeding
one receiver.

D Peter Maus' discription from another thread:
"Each antenna was connected to an RF preamp with a gain of 2-6db.
The outputs of the preamps were combined through resistive pads (for
isolation) into the RF input of the BC-794. The result was nothing
short of amazing, with fading distortions dramatically reduced, and
program listening, was quite pleasant. Even my wife was no longer
critical of SW listening."

My Mini Circuits ZFSC-2-1 has been tested and found to have better
then 25dB isolation from 250KHZ to above 30MHz., with less then 3.5dB
loss so I could dispense with the preamps. It only "cost" me an couple

of hours and I was able to listen during the test. The only time
"wasted"
was the few minutes spent spooling out my field antennas and pushing
a ground rod 4' in the ground. Not the best gorund, but good enough
for
some quick tests.

It is clear the idea has merrit, but it is also clear that to be
effective and
more then a toy some serious design work will be needed. Since I
already
have too many projects under way, this one will go in the big dream
book
of ideas that I hope to pursue when I retire.

Terry