Two TRX to One PA Switch Matrix for HF Inband Contesting
HF inband contesting is a big fun - but only when you use proper equipment :)
2na description by S53RM
Block diagram shows the simplicity of the 2na1 gears (we call it "QSO Generator Box").
The whole idea is to use one PA with two radios, each with its own antenna.
If you are tempted to build one, here is a list of features you should take care of:
- isolation between the TX-to-RX on the upper 3 relais (same holds for the lower 3) shall be 90dB+
- crosssover switch is used to temporary switch between the RUN and INB
antenna (i.e. INB is using RUN antenna - useful when chasing inband
MULT)
- RX lines out and in (useful when using mutiple RX antennas with external switch box, like 6na4
- NO INB input used to signal on wich bands there is no INB TX antenna
(like 160m and 80m, where RUN and INB use the same antenna for TX and
dedicated RX antennas for RX)
- PTT sequencer (SQN) that serves as a hardware interlock between RUN
and INB and MULT PTT inputs (MULT PTT in would be used when
adding
another radio with another inband antenna to the setup); on
important feature of the SQN is ping-pong interlock mode (described here)
For even more ambitious inband contesting one can use 3na1 QSO
generator box, where the name suggest that you wire 3 radios through
one PA to 3 antennas. The block diagram should reveal all of its
function. RX switching complication was added that alows swapping
current non-TX antenna to RX-radios when not having 3 independent TX
antennas.
