I did some measurements today on the new 6×2 design with 7/16″ connectors and it was well over my expectations. I had to compensate a bit with an inductance in series with the input on both radios to get the insertion loss down but when that was done it looked really great. Even without those modifications the result is pretty good.

Never did the attenuation between radio 1 and radio 2 go over -70dB up to 50 MHz (!) which is just UFB. Also the insertion loss up to 30 MHz never goes over 0.1dB which is acceptable and at 50 MHz around 0.2dB so the device is usable also on 6m. The best case scenario is when using one radio on antenna 1 and the other on antenna 6. Then the attenuation between the ports on 50 MHz was -80dB and on 30 MHz about -90dB which is according to me spectacular. The insertion loss is typically 0.08dB on 30 MHz and 0.05dB on 14 MHz.

The measurements were done with a ROHDE & SCHWARZ vector network analyzer with an IF bandwitdh of 1kHz, 1-50MHz range and 5 average samples.

Below you can see the plots

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Today I also assembled the 6×2 switch with 7/16″ connectors. I am gonna test this one and publish the results of insertion loss and isolation between the radio ports. If I am happy with the result I will go on and build one more box to “complete” my antenna switch system at SJ2W.

The copper plates between the relays are to decrease the coupling between the relays. I have not done much measurements on this except that I noted that I got a few more dB attenuation between radio A and B when I did measurements a long time ago, on my standard 6×2 design for SO239 or N. These boards will be possible to buy, also the regular 6×2 boards are sold if there is interest.

The reason that I have cables between the radio input ports and the board is because there need to be compensation for the capacitance in the board and this is done by adding an inductance in series with the input. I have successfully done this with the old boards. I will though measure and see if a straight wire is enough inductance or if I need to have a turn or two (air wound coil).

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Since I decided to use 7/16″ for all antenna switching after the amplifiers at the station, I needed to design a new type of powersplitters since the old design just used SO239 or N connectors. I came up with a rather neat design of a powersplit which has got an high isolation A/B output as well, which means we can route the signal to/from the powersplitter to either output A or B. This really makes it simple to create an antenna switch system for four radios with just adding a couple of 6×2 switches as well. I expect the isolation between these two ports to be at least 65dB on 10m but I will post measurement results later.

The powersplitter uses a UN-UN balun (2.25:1 ratio) to match either two or three antennas to 50 ohms and when just using one antenna the signal is routed straight to the antenna to either the A/B outputs. The relays used are the same kind as microham uses, VSB-12STB and are SPDT 16A relays.

Here are the pictures of the current progress. Hopefully I will finish up at least one box this weekend so I can post some results of the measurements.

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