WA1GFZ
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« on: October 02, 2010, 04:28:08 PM » |
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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.
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WA1HZK
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« Reply #1 on: October 06, 2010, 10:02:19 PM » |
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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
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WA1GFZ
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« Reply #2 on: October 07, 2010, 10:44:01 AM » |
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Art Collins would never approve that good idea and is flipping in his grave at the thought.
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KM1H
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« Reply #3 on: October 07, 2010, 11:10:35 AM » |
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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  |
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz
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« Reply #4 on: October 07, 2010, 11:36:35 AM » |
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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
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. Easily done in DSP.
Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."
There's nothing like an old dog.
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KE6DF
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« Reply #5 on: October 07, 2010, 11:54:07 AM » |
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Another solution would be to use a larger ceramic feed through. Here are some: http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspxNote the one with a 1 1/4 " mounting hole. Surely that thick a ceramic layer would handle some serious HV. |
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W2VW
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« Reply #6 on: October 07, 2010, 12:34:24 PM » |
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RTV silicone.
Give at least a full 24 hours to cure.
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WA1GFZ
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« Reply #7 on: October 07, 2010, 04:11:10 PM » |
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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.
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W7SOE
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« Reply #8 on: October 08, 2010, 01:03:08 PM » |
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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 |
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Ed/KB1HYS
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« Reply #9 on: October 08, 2010, 03:20:51 PM » |
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Nice products at that Daburn site. Seems to be a wholesale outlet though. Too bad, those porcelin insulators looked mighty nice.
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73 de Ed/KB1HYS
Happiness is Hot Tubes, Cold 807's, and warm room filling AM Sound.
"I've spent three quarters of my life trying to figure out how to do a $50 job for $.50, the rest I spent trying to come up with the $0.50" - D. Gingery
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W7SOE
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« Reply #10 on: October 08, 2010, 05:07:10 PM » |
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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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KM1H
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« Reply #11 on: October 08, 2010, 08:40:46 PM » |
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