Sunday, October 7, 2018

Some more on RF hookup

Just putting some options out. The need is a ground plane and isolation of input and output. Shielding is good too. So what materials are available?
Electrical junction boxes are a good option. These come in 1/2" up to 2-1/4" depth. I paid 79 cents for this one. I have not seen any project boxes for less than a dollar in quite some time. (it is 2" x 4" x 2-1/4")
They come with fitted screw on covers so they provide good shielding too.
RCA connectors are easy to find and the cables can be bought pre-made.
You can get them in 1' to 12' (maybe even longer).
BNC connectors are the old standby.
I like the twist on connectors, no soldering required.
I have two RCA connectors installed here.
The outside view.
The BNC connectors.
The RCA connectors.
Here I have an adapter. Connects a BNC to RCA.
Here we have a feed thru capacitor. It is 1nfd from the connectors to the shell.
They can be used to feed power or signals.
A cut away of the feed thru.
I made this box from a piece of sheet tin. Just one more possibility.
Here is a feed thru cap. You just drill a hole and solder it in place.
One last option to consider. You can just buy the covers and use two. The screw holes line up so you can use long screws and spacers to make the sandwich. A sheet of tin bent to fit inside the lips will finish the box. You could screw it shut and wrap the outside with aluminum tape, copper tape or even aluminum foil. Just cover the gap with metal.

One last thought here. You could isolate the two sides of the cover with an L bracket and use a feed thru to carry the signal through it. Just remember the comments in the last post. Keep the input and output as far away from each other as practical.
I put the BF970 amp on this board. It worked very well up to 20 Mhz. My scope and signal generator only go to 20 Mhz so that is all I can report with actual testing. I connected it to and antenna and fed a receiver. It made a good preamp.

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