2BSIQ SO2R with Flexradio-6700 and N1MM+

To be able to work high rates on contests there are several techniques. Popular is of course SO2R but there several methods to accomplish this. Jose CT1BOH suggested the 2BSIQ technique which is quite attractive.

The fundamentals are:

1. Send TX on radio A and listen with both ears on radio B.
2. When you end TX on radio A you get stereo mode and hear both radios in the ears.
3. When you start TX on radio B back to both ears to radio A.
All this done automatically w/o tilde button.

Here is a video demonstrating it. There is no CW side tone sound as you always listen to other radio for callers while sending CW on the other radio.





More about this technique from Joses material: http://www.qsl.net/ct1boh/2bsiq/?tube=.

Band isolation key to successful SO2R on multiple bands

To be able to work simultaneously on two adjacent bands like 40 and 20 m the isolation needs to be at least 90 dB. Of course this will depend on the following:

  • antenna isolation –  can be as low as 30-40 dB with close antennas or resonant antennas on harmonics.
  • antenna port isolation on the transceiver- on the Flexradio series 6000 it is about 40-50 dB between the antenna ports.

So in total an isolation that can be as low as 70-90 dB. But is this a problem? Well with a 1.5 kW station you have a signal level of around +62 dBm which is way over S9+73 dB!!! And your station can not handle more than +10-20 dBm.   To be on the safe side and also having the joy of working SO2R a good thumb of rule is at least 150 dB of isolation. This means that with a 1.5 kW station sending on say 40 m you will not have more than  S 8 (+63 – 150 dB = -87 dB) . In this exercise I have more or less ignored effects of phase noise and second harmonics (which with an old TRX can be severe).

With my set-up I end up in the following isolation between the antennas and 4o3A High Power bandpass filters (they provide about -50 dB of isolation) :





As you see about 90 dB (green lines). To this we must add the transceiver isolation of 40-50 dB. So in total 130-140 dB of isolation or S7-S9. Not too bad. That is you may send with a kW on 40 m and do listening on 20 m with a 40 m signal at about S7-S9.

My remote dx and contest station SM0HRP

Here is my remote station set-up.

New updated version of schematic.
My FlexRadio 6700 and SO2R set up with OM2500A:s.
My high bandpass filtres.



































The present antennas.

3 el 40 m yagi.


3 el 30 m yagi.


Previous XR5 stack under replacement by new JK2015 stack 4/5 on 20/15 m.


New 24 m HD tower for the JK2015 stack.