RF Chain Construction

And here is the completed RF chain, including the 10MHz crystal calibrator in/out and power wiring. If you look closely just behind the rear panel, you can see some of the cabling that connects RCA In/Out jacks between the various stages. I attempted to have In and Out jack pairs be as close as possible to each other to minimize cable runs, however, in some circumstances there had to be crossovers due to the design of the PC boards themselves.

The cables were constructed from RG-58 coaxial cable, with the plastic sheathing removed. I had hoped to use RG-174, but it's center conductor is simply too fragile when you are attempting to get a completely sealed coax run from tip-to-tip. I also tried using some special Teflon coated center conductor mil-spec stuff very much like RG-174, but the plastic sheathing was VERY difficult to remove without damaging the shield.

Per Wes, W7ZOI, I was very careful to NOT use normal tip and ring RCA plugs, opting for some plugs I found at Dayton the prior year. These plugs have the ring extend all the way around the plug, narrowing to a point where it extends nicely into the shield--that is, the shield of the coax extends all the way to the end of the ring, not just to a connection point in the plug. About an inch and a half or so of shield is removed, and then about 1/2 inch of insulation is removed from the center conductor and it is tinned. Then about 1/2 inch of shield is opened up so that it can be easily formed all the way around the ring. I then soldered the center conductor into place, alternating between putting the soldering iron on the tip and needle nosed pliers as a heat-sink, so that I never overheated the center conductor insulation. Then I soldered the shield all the way around the ring, again alternating between iron and pliers so that it never got too hot.

I read in one of Wes' online articles that another way to do this is to take a piece of shield, removed from the rest of the coax and solder it all the way around the ring on the connector. Then insert the center conductor into place and solder it. There should be some overlap of the shield soldered to the ring and the coax shield. Slip a piece of heat shrink over this and heat it up to make a nice connection between the two shields. Don't know how mechanically solid this is, but it's got to be a lot easier than my method!