I made a cable to temporarily set up the beverage switching to two radios before the openASC control system is implemented into the station. I decided to use the LPT port of the linux server running at the SJ2W site and I did an easy to handle web interface to switch between the different beverages, just 8 click buttons which each select a different beverage antenna.
The 4×8 switch which can be seen below can route eight different antennas to four different radios. One can select one beverage at the time on each radio and by adding bandpass filters to each radio one can listen to the same beverage without any 3dB drop. That is still to do though but a prototype has been tested and it seem to work, based on slightly modified OH2U filter design.
I did some measurements on the beverage box to see what kind of cross coupling there is between the different channels. Since I am limited to two layer boards the routing is not easy to do in a optimal way RF-wise but considering it’s meant to be used on lowbands it is not as big problem as on the other 6×2 switches I have designed.
The insertion loss on 40m was typically around 0.17dB while on 160m the insertion loss was around 0.06dB which is just fine for RX antennas (even for TX…). The cross coupling between different antennas were as worst -45dB while using radio 1 was using ant 1 and radio 2 was using ant 2. When radio 1 was using antenna 8 and radio 2 was using antenna 1 the coupling was -63dB which is just fine. When radio 1 was using ant 8 and radio 2 using ant 4 the cross coupling was -65dB. So it varies a little depending on ports but the “bad” combination seem to be channels right beside each other. One could maybe improve this by soldering copper planes between the relays but that is too much work with 32 relays. The cross coupling between radios were typically around -50dB on 40m. All values listed above if not noted otherwise was measured on 40m. On 160m the cross coupling was typically -90dB or better except when having a port right beside each other, which reduced the coupling to around -60dB.
This weekend we’ll hopefully hook the switch up at the radio QTH so stay tuned for the end result.
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