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.

New 24 m HD Tower project on-going with JK antenna stack.

Since Sept 2017 we have been working on configuring the new 24 m HD Alu tower that we installed just after the vacations. The mast weights about 1200 kg and is cable of 2 square meter of antenna load without any guying!

The tower will carry two JK 2015 antennas in a stack. An electric winsch that is remote controlled adds to the flexibility of the tower.

 

How to add remote contest capability to Flex-6000 without a remote PC

Flex-6000 series is a great contest radio. However, when running contests from a remote location present SDR software cannot produce local CW sidetone unless you use the built in CWX keyer and NOT use a logger program to automate it all. Same with Flex Maestro who does produce local sidetone but you cannot integrate with a local PC contest program (easily).  Flex will eventually come up with a solution soon but till then we need a solution. The solution is the Remote Rig concept. Easy and not expensive (you may find these at the local swap market).

How to do it

You may use Remote Rig boxes to produce local CW sidetone very easily. At the remote radio end I have no PC (to risky in my opinion) only the remote rig 1258 MKII radio box. This box has CW keyer output that I connect to the FlexRadio front panel CW key input . It has also a Audio input that I connect to the FlexRadio front panel Audio output. At home base I have the Remote rig control box which is connected with a USB cable to my PC with N1MM or WriteLog. The control box automatically creates virtual COM Ports for CW keying with Winkeyer emualation (at the radio end) that I choose in the N1MM configurator for CW keying.
So when I do N1MM or WL CW keying at my home base PC the remoterig radio box keyes the FlexRadio. At the same time the audio output from the FlexRadio is routed back to the Remoterig control box at home base and I can hear the CW side tones. This works very well and is 100 % rock solid.
No VPN is required. Just regular internet. SmartLink can be used. The bandwidth required is about 300 kbit/s depending on the audio quality of the remote rig audio (there different compression levels).
With the remote rig boxes comes two COM ports that you may use to control RS-232 devices as well. Rotors, wattmeters etc. You van attach your Morse key paddle to the remote rig control box and get local sidetone as well as keying the Flex remotely.
So this is the only way today to get local CW side tone when doing remote contest CW.

RRC configuration

Here screen shots from the confuguration pages of the RRC boxes. I use COM Port 3 (COM Port 1 may also be used with a USB cable). Just find the corresponding Windows COM port (in the device manager) and use that for CW keying in the logger program. That´s all to it. 🙂