Peter, the 572B has the same basic form as the 811A which is rated to 54
MHz. Just because Cetron built an audio tube and simply said 30MHz sounds
like a good number doesnt mean its gospel.
The first SB-200 conversion I saw was in the early 70's when one was bought
to me after the owner tried some idiotic magazine article. This was pre
computer so I actually had to do some work to make it fly. The design
evolved from good to perfect as I bought several to experiment with.
I get 55% with good tubes. Output averages 700-750W with 75-80W drive and
some are super "hot" like this last pair.
Unlike the FL-2100B which is probably more popular in the UK, the SB-200 is
very easy to tame on 6. I "discovered" the FL-2100 bogus neutralizing
circuit about 15-20 years ago and W8JI has mentioned it recently as well.
Carl
KM1H
----- Original Message -----
From: "Peter Chadwick" <g3rzp@g3rzp.wanadoo.co.uk>
To: <amps@contesting.com>
Sent: Monday, September 24, 2007 6:55 PM
Subject: Re: [Amps] stability of amps
>I suspect the real question is:
> Does anyone have the s (or y or z) parameterts of the 572B at frequencies
> up to 50 MHz and beyond? This would tell you the potential stability.
> My experience with 572Bs is that they are a real wotsit at 10 metres
> anyway, and personally,. I'd avoid them like the plague
> Obviously, Carl can tame them on 6. He's a a braver man (or some would
> say, a better engineer) than I am to attempt it!!!. What sort of efficency
> do you get, Carl?
> 73
> Peter G3RZP
>
>
>
>
>
>
> ========================================
> Message Received: Sep 24 2007, 11:35 PM
> From: "Steve Thompson"
> To: amps@contesting.com
> Cc:
> Subject: Re: [Amps] stability of amps
>
> c.s. wrote:
> !
>> Primary to my problems is the question of stability of the
>> SB200 on 10 mtrs.
> How does the instability show - what frequency is any oscillation at?
>
> Steve
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