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[VE7RF]

10 KW CCS ON 6M...USING THE 3CX-6000A7... PART 15

The bypass SWR ended up being aprx 2.5:1 Various fixed cap value combo's were tried, (including a temp air variable), wired between the NC contact of one of the RJ2B's..and chassis. The lowest bypass SWR was a lousy 1.8:1 The way the cap to ground trick works is it amounts to a shunt C and a series L, (XL of relay's NC to COM path) ... and transforms the Z down a bit, and swr drops. Easier to explain on a smith chart.

The XL of the RJ2B is too high a value for the cap to grnd trick to work. Ok, PLAN B. 70 pf wired in SERIES with the NC contact of the RJ2B ( then smaller RG-400 to the NC contact of the smaller RJ1A input relay. In this config, the 70 pf
( 44.58 ohms of XC) cancels out the XL of the RJ2B.

Ok, now bypass SWR is down to 1.2:1 good enough. A 44.5 pf and a 24.5 pf HT-58 doorknob are wired in parallel to make the 70 pf. Both are NP0 types, don't drift, and handle a LOT of current on 50 mhz. They have to be able to handle the 1200 watts from the SS IPA on 50 mhz, on bypass mode. SS amps don't like SWR, and the ALS-1306 does not have a built in tuner. So the issue was fixed right at the source.

I believe this might be the 1st time a series cap has been used to cancel out a relay's XL. The drawback is... the 70 pf ends up being a LOT higher XC as freq decreases. Like 1263 ohms on 1.8 mhz. Happy Xmas everyone. Jim VE7RF..and Scott, KB1SEL

https://www.youtube.com/watch?v=hI3D_QvmkM8