2na1 (2on1) -  Two transceivers to one power amplifier - box

(S53CC, S51RM, S53WW and S53RM)


After successful WW CW contest expedition to Corsica (TK0C M/S 2015), Boris – S53CC gave me a task to construct switching box, that allows two transceivers alternately use one power amplifier with two antennas (»RUN« antenna and »INBAND« antenna for S&P). Such switching box is replacement for one power amplifier with some added functionalities.

At start we only have wide guess how much attenuation we have between inband and run antennas, so some simulations and field measurements were necessary. Robi – S53WW was a leader of that task and we came to conclusion that 90dB of attenuation between RUN and INBAND ports on 2na1 box will be enough. We achieved 93dB on 28MHz.

After it was decided to go TK0C M/2 in WW CW 2016 contest (practically the same hardware as year before for M/S, with few additional antennas) we decided to add PTT interlock for third transceiver with separate power amplifier (MULT / second INBAND position). MULT is in fact band change station seeking for mults or ordinary QSO's on other bands. Eight band changes are allowed per hour for each of two positions in M/2 category. (RUN1 and RUN2.) After 8 band changes are spent, MULT station can go to second INBAND position with its own »mult« antenna and its own amplifier.


Functions of 2na1 box:

1)      Handling PTT for 3 transceivers and one PA with interlock and switching delays. This handling has two modes: simple interlock and interlock which prevent first and second INBAND station to go TX one after another. That kills pile up on run station.

2)      Signaling at each transceiver witch position currently TXing. (We use colour coded approach with table tennis balls illuminated with colour LED).

3)      In case of only one TX antenna for band (in our setup it was 160 and 80) 2na1 box have to prevent transmitting on empty port automatically (with band decoder) or manually.

4)      Crossover function witch switch over INBAND and RUN antenna on TX and RX simultaneously.

5)      RX OUT and RX IN connectors on 2na1 box for implementing RX antenna switch with additional RX filters and limiters. Using RX IN on transceivers is not necessary any more.

Here are some pictures:





2016-11-25 21.50.02


Here is PDF of shematics and PCB

73 Sine - S53RM