K5LAD SO2R Setup
I don't often use a Single
Operator 2 Radio (SO2R) operation but during a recent contest I decided to set up my
station this way. I had several coaxial antenna switches so I used them to set this
up. I actually mounted three switches (S1, S2, & S3) flat on a spare piece of 2
x 4 lumber about 15" long and this worked well. I needed to figure out the
switching "truth table" for the switches and the document below shows the
result. The switches are identified as to their particular switching task. The
letters P1, P2, P3 etc. represent the position 1, position 2, position 3, etc. of the
switches. Some switches only have two positions, one has as many as five positions,
although not all positions were used. If the truth were known, the table and diagram
were prepared to jog my memory when it came time to operate. I could have traced the
cables each time but I found this a lot easier in my advancing age.
Switch S1 is a B & W #593, a
3-position switch used to choose which radio will feed the primary system. One
position is labeled "Bench Antenna" but a more appropriate label would be
"Bench Radio" as it is a rig input and not an antenna connection.
Switch S2 is a B & W 5-position
rotary switch with only 2 positions of the 5 being used. This switch allows me to
actually have the two radios hooked to its own antenna at the same time. The secret
to this is the use of an LDG AT-100Pro Autotuner which has a single input but a switchable
output to two antenna jacks.
Switch S3 is a standard 2-position
switch like the MFJ-1702. It is used to choose whether Radio #2 is to go through the
LDG Autotuner and into one of the two amplifiers or to the S2 switch and switch to a
second antenna, which happens to be a Cushcraft R-7 vertical.
Switch S4 is also a standard
2-position switch like the MFJ-1702. It chooses which amplifier will be with the RF
signal from one or the other radios.
The LDG AT-100Pro Autotuner is
actually used to provide a tuned input for the amplifier. This information is also
discussed in another area on
these web pages. Actually, the Dentron GLA-1000 already has a tuned input now
but the Dentron MLA-2500 did not and I found it to be very helpful and worthwhile to have
it. An extra benefit is that the AT-100Pro can be used as a regular autotuner when
attached to an antenna or switch in position 2.
This system allowed me to quickly
choose which radio I wanted to use, choose which amplifier I wanted to use (actually the
second one was to be a stand-by amp....... just in case). I did not have to use it
in the contest but it would have been ready. The second radio, with the ability to
have it hooked to a resonant antenna, made it convenient to listen for a band opening on
The drawing shows another 2-position
switch to choose the output of the chosen amplifier. In truth, I didn't have another
handy switch so I actually changed this one over manually.
I don't know if any of this information will
be helpful to others but it has helped me. -- Jim - K5LAD
Created August 2, 2007
Last updated 11/06/2012 16:59:22 PM
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