[Amps] SB200 on 6m & my take

[Steve Katz]

AFAIK manufacturers rarely specify a maximum frequency of operation.  However, it's common to specify a maximum frequency for full power ratings, such as Svetlana has done on their 572B data sheet: http://www.g8wrb.org/data/Svetlana/pdf/572B.pdf  where they list "max" as 30 MHz.

In reviewing the "Chinese" manufacturers' data sheets, it appears most of them specify the 572B as an audio amplifier, and some only rate their versions to 1500Vdc!  I guess if any of those end up in ham amplifiers the users will be pretty surprised...

WB2WIK/6

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
Behalf Of Carl
Sent: Friday, March 13, 2009 9:44 AM
To: KB0NLY; David Craig; amps at contesting.com
Subject: Re: [Amps] SB200 on 6m & my take


What spec sheets from what manufacturers?

Please cite actual examples.

Carl
KM1H


----- Original Message ----- 
From: "KB0NLY" <kb0nly at mchsi.com>
To: "Carl" <km1h at jeremy.mv.com>; "David Craig" 
<davidhcraig at verizon.net>; <amps at contesting.com>
Sent: Friday, March 13, 2009 11:36 AM
Subject: Re: [Amps] SB200 on 6m & my take


> Since all the spec sheets from all the manufacturers said so.  They 
> hardly hold their own at 10m.
>
> 73,
>
> Scott
>
>
> ----- Original Message ----- 
> From: "Carl" <km1h at jeremy.mv.com>
> To: "David Craig" <davidhcraig at verizon.net>; <amps at contesting.com>
> Sent: Friday, March 13, 2009 8:45 AM
> Subject: Re: [Amps] SB200 on 6m & my take
>
>
>> I'll be briefer. Since when isnt the 572B rated to 6M?
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message ----- 
>> From: "David Craig" <davidhcraig at verizon.net>
>> To: <amps at contesting.com>
>> Sent: Friday, March 13, 2009 12:44 AM
>> Subject: [Amps] SB200 on 6m & my take
>>
>>
>>>    Brief & to the point- they stink, monoband or (worse) tapped
>>> bandswitch "models".  They may be fine for the occassional SSB QSO
>>> without pushing it, but otherwise they do one thing with regularity-
>>> they die/burn out/self-destruct.  RTTY? WSJT & other digicrap with
>>> 100% duty cycle for 30-55 seconds key-down?  Result?  Be ready for a
>>> buzz, hiss, POP & Boom & to buy a new amp, or parts that cost enough 
>>> $
>>> to build a new one.  I don't do any digital myself save cw but if 
>>> you
>>> want a list of dead SB200 conversions (owned by others) I'll be 
>>> happy
>>> to provide them, some were EME deaths & others that just "crapped 
>>> out"
>>> due to tubes that aren't ment to be used at that QRG.
>>>    I don't care what you can "get away with", I want something that
>>> isn't going to crap out because the tubes aren't rated for 50MHz 
>>> use.
>>> SB200s should be left to HF.  If you are still going to convert one,
>>> do what I am doing and put a 3CPX800 in it with new cooling and a 
>>> new
>>> FWB PS and appropriate transformer.  Otherwise build one with an
>>> appropriate tube/s from scratch which I have also done x 3.  572Bs 
>>> are
>>> a lousy tube for 6m conversion unless your habit is to run it a few
>>> hours per year.
>>>    Oh, one last thing- for parasitic suppressors, don't be lazy and
>>> use the resistor leads as a soldering surface for the L (really a 
>>> "U")
>>> between resistor sides on a 6m conversion.  I have seen 4 cases so 
>>> far
>>> of that method resulting in heat melting the "L" on the plate-block
>>> side... ergo all B+ plus RF current passes thru the resistors &
>>> softens the tubes in seconds. $600+ $ down the tubes.
>>>
>>>    N3DB
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
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