The AM Forum

I can't seem to be able to reply to Todd's story. Todd I have used teflon tubing over the threaded rod as additional insulation and voltage break down on that type feed through. You can go down a size on the rod to be able to add more insulation. That thin layer of ceramic is is not much for a 5KV peak modulation voltage. I would also make sure the hole in the chassis has no sharp edges.

For what it's worth I destroyed several of those during the 833 rig construction. They don't actually do high RF volts too well. I ended up punching a larger hole in the chassis and mounting a square of plexiglass which I drilled to mate the insulator ceramic hardware. Problem solved.
Keith

Art Collins would never approve that good idea and is flipping in his grave at the thought.

An exposed ceramic HV feedthru was the accepted method even in QST before hams no longer were required to take responsibility for their actions.

My method as a 17 year old was to run 2500V using a sawed off piece of a bicycle handgrip stuffed thru a hole in the chassis in the rear and top using some #20 or so insulated wire going thru insulated washers glued into the grips. Im still here to talk about it ;D

heheheh...  nice!


My first homebrew project at 13 years old was to "try" to build that 200w 811A linear amp in the 1964 handbook. Wow, it said 200 watts!

I took the metal box shell of my Gilbert chemistry set and drew out the single socket hole. I just guessed at the socket size. I didn't have a drill or punch, so with a hammer and nail I proceeded to hammer out the large hole. The chemistry set collapsed and that was the end of my first project.

JSing has never been more refined than on that day.

T

Another solution would be to use a larger ceramic feed through.

Here are some:

http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx

Note the one with a 1 1/4 " mounting hole.

Surely that thick a ceramic layer would handle some serious HV.

RTV silicone.
Give at least a full 24 hours to cure.

Hey Tom that was also my first Linear also but I bought a cabinet at Hatry's.
Got plenty of advice from Corky and Ward. Worked a lot of DX with it.
Later I added a second tube in parallel. Then I was banished to the basement because my shack in the bedroom was right under the TV antenna and Dad was not happy that I could take out the TV and break connections on the phone.

I have been looking for HV feedthrough connectors and these would work.  The Millen ones are too expensive.

That place has a great selection but you have to buy 25.  :-(

Anyone know of a place to buy the "beehive" type feed-through connectors?

Thanks

Rich

Nice products at that Daburn site.  Seems to be a wholesale outlet though. Too bad, those porcelin insulators looked mighty nice.

OK, who wants to go in on some beehive insulators?

Rich

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