Re: [Amps] HV limit for rfc-3 choke?

["Carl" <km1h@jeremy.mv.com>]

Ive used the wirewound.glitch resistor extensively as the second choke as 
they are both inductive and resistive at RF. Placed right after the main 
choke and with a .0047 uF 10KV disc at both ends fulfills the bypassing and 
choking requirements. Paralleling a pair at the PS end can also be done.
With 3400V at 2A + and the Ameritron choke several 77SX's and modified 
LK-800's are happy on 160.
Carl
KM1H


----- Original Message ----- 
From: "Leigh Turner" <invertech@frontierisp.net.au>
To: <amps@contesting.com>
Sent: Wednesday, March 26, 2014 1:13 AM
Subject: Re: [Amps] HV limit for rfc-3 choke?


> Excellent figuring Peter!
>
> An additional choke and bypass cap is almost essential to prevent
> deleterious 1.8 MHz RF blow-by into the HV power supply electrolytics.
>
> Mind you the HV "glitch" resistor also provides some attenuation of RF
> leakage when bypassed with a ceramic cap.
>
> Leigh
> VK5KLT
>
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of peter 
> chadwick
> Sent: Wednesday, 26 March 2014 8:48 AM
> To: Carl; Rich Hallman - N7TR; amp reflector
> Subject: Re: [Amps] HV limit for rfc-3 choke?
>
> 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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