[Amps] Tube choice for SB-200 on 6 meters

[David Craig]

    I'll defer to the comments of others on the 572b insofar as stability at 
50 MHz is concerned.  One thing however is a virtual certainty- 572b 
conversions (at least SB200s) do not hold up with hard duty-cycle use such 
as digimodes or contest-style operating at 50 MHz.  Be it the inadequate PS, 
the tubes, or whatever, regardles of the style of monoband conversion it 
needs to be treated with kid gloves.  If it is all you can do, then I'd say 
go for it as it is better than nothing, but don't hit it too hard.  73 N3DB


----- Original Message ----- 
From: "Larry" <n1miw at cox.net>
To: "'Carl'" <km1h at jeremy.mv.com>; <Amps at contesting.com>
Sent: Saturday, July 11, 2009 10:59 AM
Subject: Re: [Amps] Tube choice for SB-200 on 6 meters


> The problem I have is that I do not know what I am doing with these tubes
> for this conversion. I have yet to come across a conversion that everybody
> agrees with. I don't want to be a "hack", I just want to get an amplifier 
> on
> the air for 6 meters, do it myself, and not spend an arm & a leg getting 
> it
> there. The amp I have was purchased for the right price - I wish it was 
> the
> 220 that I had, because of the tubes. However, since I don't, unless 
> someone
> can tell me how to do the conversion SAFELY, I would just prefer to change
> the tubes to ones that are rated OK at 50MHZ. Larry N1MIW
>
> -----Original Message-----
> From: Carl [mailto:km1h at jeremy.mv.com]
> Sent: Saturday, July 11, 2009 9:26 AM
> To: n1miw at cox.net; Amps at contesting.com
> Subject: Re: [Amps] Tube choice for SB-200 on 6 meters
>
>
> Obviously I do not want to use the 572B's because of the controversy
> surrounding them at this frequency. TIA... Larry N1MIW
>
>
> There is no controversy among those that know what that are doing. Only 
> the
> hacks blow them up and then send the amp to me or others to be done right.
>
> Carl
> KM1H
>
>
>
>
>
>
>
>
> ----- Original Message -----
> From: "Larry" <n1miw at cox.net>
> To: <Amps at contesting.com>
> Sent: Saturday, July 11, 2009 12:34 AM
> Subject: [Amps] Tube choice for SB-200 on 6 meters
>
>
>> Hello group,
>>
>>   I'm looking for some information on converting an SB-200 to 6 meters. I
>> originally thought about using the Russian GI-7B tube, but now I'm not
>> sure.
>> It looks like I can only use one tube due to power supply limitations.
>> What
>> have you guys seen in real-world conditions if you used this tube? Will I
>> see about 500 CLEAN watts out from the single GI-7b (someone said in the
>> archives that one of these tubes equals 2 572B's)? Can I use 2 GI-7b's
>> without letting the smoke out of the transformer or PS? There's also the
>> mod
>> for the GLA-1000 where the output watts is ~750 which I'm using for
>> comparison, but I don't know what the current was at that limit. The spec
>> sheet for the GI-7b might put the current for 2 tubes at close to 1A,
>> which
>> the SB-200 can't supply as far as I know.
>>
>>   If the single or dual GI-7b can't give me 500 watts+ out from the 
>> SB-200
>> PS, is there another tube (or tubes) of choice you would recommend for 
>> the
>> SB-200? Obviously I do not want to use the 572B's because of the
>> controversy
>> surrounding them at this frequency. TIA... Larry N1MIW
>>
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>
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