[hpsdr] Diversity performance?

[K1rqg at aol.com]

David and all
 
I have been using K5SO diversity software for quite some time now, months,  
and
during this time I have transitioned from using 2 horizontal antennas (80  
meters),
to using 3 selectable RF probes. I am trying to document the hardware  
aspect of
my setup and let the software speak for itself. 
 
I am still experimenting with different antennas at this time, but bad  
weather has
slowed my progress. My initial tests with the 2 horizontal antennas on 80  
meters
proved to be quite effective bringing DX signals "out of the noise"  
certainly by
minimizing louder signals from a different direction. Also found it quite  
effective
to eliminate "birdies" and "UFOs" caused by switching power supplies  etc.
 
I have since gone to using 3 RF probes set up in an equal lateral triangle  
about
50 feet apart. These probes are nothing more than 3 inch square pieces of 
double sided PC board connected directly to a high impedance unity  gain
amplifier feeding RG-6 back to a software selectable (ALEX control)  
switching
system that not only provides any two of six selectable inputs, but also  
provides
RF protection for the Mercury boards. (The RF probes are about 20 feet in  
the air)
 
The beauty of the RF probes is that they are NOT resonant, and believe it  
or not, 
they perform much better than any of my wire antennas in the Broadcast  band
and work well from about 300 Khz to 20 meters. 
 
During the daytime, I can null a local broadcast station (13.5  miles away) 
by more
than 50 dBm and this holds pretty steady. However as time progresses into 
darkness and ground wave starts to fade and sky wave increases, the null  
goes
down somewhat to around 30 dBm.
 
Using diversity at night on 160 and 80 meters varies with propagation, and  
using the
same probes, I see anywhere from 10 dBm to 25 dBm null, but this is very  
dynamic
given the variations of the received sky wave. 
 
My plan is to try some larger (20 foot) probes and evaluate them when the  
weather
allows. Then I will try 3 resonant verticals as well. 
 
I find I use the RF probes on 80, 40 and 20 meters more than I use the full 
 sized 
antennas. They are very useful on 20 meters when I am talking to Europe  and
NA stations at the same time, as I can rotate the diversity control to  
"peak" up
the station in one direction and just click 180 shift for the other. I  do 
run full legal
limit on these bands, thus the need for protecting the Mercury boards even  
though
the RF probes are 100 yards from my transmit antenna.
 
In conclusion, I find the diversity software extremely useful, and  
intriguing to experiment
with. I also would like to hear from others about their experiences  and 
how they 
use it. If anyone has any other questions regarding my set up, I will  be 
happy to 
respond.
 
I want to thank K5SO & W5WC for their continuing improvements of the  
PowerSDR
software as applied to HPSDR, and of course thanks to FLEX radio and KD5TFD 
 as
well. 
 
73 de Joe
K1RQG 
 
 
In a message dated 3/8/2011 2:00:01 P.M. Eastern Standard Time,  
dwoodhead at bms-inc.com writes:

*****  High Performance Software Defined Radio Discussion List *****

For  anyone that is using dual Mercury boards in a diversity setup;  how
effective do you find it in suppressing local and distant QRM (using  2
antennas)?  

Thanks

David
KM5TZ
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