On a 2 x 4-1000A I used approx 3 turns 1 inch dia
and 1 inch long coil on each tube. However I newer
could get Globars or any other good resistors and I
was too cheap to order any from the US. Instead I
took a ferrite rod and put that inside the
coil. The amp was 160-10m and worked just fine.
Jim SM2EKM
-------------------------
On 2010-07-15 22:00, Carl wrote:
> Agree with Dave. In the past I turned out many 1-2 holers grid or cathode
> driven to order; most covered 160 or 80-10M. Then I used 20-25W Globars or
> surplus 68 Ohm 50W Carborundums which I bought almost 100 in sealed packages
> for real cheap.
>
> Stopped that when all the local AM stations used the tubes until they were
> even almost dead as modulators or went SS. I did about 10 3CX3000A7's and a
> few 4CX5000A's after that.
>
> Carl
> KM1H
>
>
>
> ----- Original Message -----
> From: "DAVE WHITE"<mausoptik@btinternet.com>
> To:<amps@contesting.com>; "Rob Atkinson"<ranchorobbo@gmail.com>
> Sent: Thursday, July 15, 2010 3:34 PM
> Subject: Re: [Amps] parasitic suppressor voodoo
>
>
> On a 2 times 4-1000A amp (5.5kv, grounded grid, cathode driven) I used two
> separate parasitic suppressors, each with 3 paralleled 50 ohm carbon
> resistors inside a 15mm diamater two-turn coil of 2mm copper wire over about
> 10mm length. The amp has worked flawlessly (80 thru 10m) for many years.
>
> If yours is a low band amp, you could probably make REALLY certain by
> increasing the number of turns on the coil. Initially with four turns the
> resistors smoked a little on 10m. I guessed "too much L". There was no
> science to building these suppressors - it was a case of looking at the
> W6SAI "Radio Handbook" and seeing if it worked. Voodoo? Maybe.
>
> I didn't try the amp without parasitic chokes but it seemed to work and "if
> it ain't broke, don't fix it"....
>
> Hope this helps
> Dave G0OIL
>
> --- On Thu, 15/7/10, Rob Atkinson<ranchorobbo@gmail.com> wrote:
>
> From: Rob Atkinson<ranchorobbo@gmail.com>
> Subject: Re: [Amps] parasitic suppressor voodoo
> To: amps@contesting.com
> Date: Thursday, 15 July, 2010, 18:40
>
> I would love to know what if any p.s. is needed on a pair 4-1000A at
> 4.5 KV triode connected cathode driven for 160, 75 and 40 m.
>
> rob
> K5UJ
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