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@jeremy.mv.com>
To: "David Craig" <davidhcraig@verizon.net>; <amps@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@verizon.net>
> To: <amps@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
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>
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