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Author Topic: plate DC lead routing inside the RF enclosure  (Read 3027 times)
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Patrick J. / KD5OEI
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Posts: 8267

« on: July 05, 2010, 05:13:05 PM »

I had to move the plate RF choke so it is very close electrically to the junction of the plate and the coupling capacitors of the pi network. This corrects the original builder's mistake of having a 20" copper strap line between the plate and the RF choke. I am sure this plagued him with TVI and parasitic oscillations to no end.

I added a 500pF 30KV RF bypass capacitor at the base of the RF choke. I left the original 500pF 30KV bypass capacitor in place near where the HV goes in.

Now the HV point is about 28" by wire from where it was. This is a large size box above the chassis, about 24"wx18"hx24"d  with a 4-1000.

I can run the HV lead against the inside of the plate enclosure wall from the choke & the added RF bypass capacitor all the way around to the original RF bypass capacitor for a total of 28". Is this a bad idea?

The transmitter size is 1KW DC input on AM with full modulation and runs 3000-3500V on the PA plate, if that makes any difference.

The RF deck is out of the cabinet for having the grid circuit rebuilt so I don't have a way to test anything until that is done.

Radio Candelstein - Flagship Station of the NRK Radio Network.

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Posts: 11151

« Reply #1 on: July 05, 2010, 06:39:51 PM »

Get yourself a length of RG142 and use it as the high voltage lead. Ground the shield at both ends and expose at least an inch of dielectric so it doesn't flash to the shield
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