Figure it this way:
Suppose you have 5kV DC and a plate swing of 8kV p-p or 2800 RMS. 225
microhenries is 2545 ohms at 1.8 MHz so the RF current in the choke is 1.1
amps, in addition to the DC. If Q = 100, R = 25 ohms and the power loss in the
choke becomes 30 watts. That 1.1 amps needs a low impedance ground return, so
that means something of the order of maybe 5nF to ground. Larger values can get
too inductive on the higher bands... Even then, 5nF is 17 ohms at 1.8 MHz, so
there will be about 20 volts of RF at the base of the choke. That means you
need another choke and capacitor to keep RF away from the HV electrolytics.
I recently published an article in the journal of the Vintage and Military
Amateur Radio Society on this: I can send a copy if anyone has any interest.
73
Peter G3RZP
========================================
Message Received: Mar 25 2014, 08:30 PM
From: "Carl" <km1h@jeremy.mv.com>
To: "Rich Hallman - N7TR" <rich@n7tr.com>, "amp reflector"
<amps@contesting.com>
Cc:
Subject: Re: [Amps] HV limit for rfc-3 choke?
I know people using them at 5KV from a 4-1000 to 3CX3000; they appear to
hold up but I wouldnt want to experiment on RTTY with the 3X3 or bigger..
Carl
KM1H
----- Original Message -----
From: "Rich Hallman - N7TR" <rich@n7tr.com>
To: "amp reflector" <amps@contesting.com>
Sent: Tuesday, March 25, 2014 2:06 PM
Subject: [Amps] HV limit for rfc-3 choke?
> Will the rfc-3 choke work at 5kv? I know they say 4kv, but wanted to
> know if others are using it at higher voltages?
>
> Thanks.... Rich N7TR
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