[Heathkit] Re: Heathkit Digest, Vol 30, Issue 34

[Pat Miller]

I am fairly new at this, but will share my experience with my SB 200.  I 
bought it off eBay. I did the Harbaugh upgrades because my meter was only 
reading about 1200 vdc  & I measured the voltage to be around that 2400vdc 
level. Anyway, I did the mods. The amp had 2 mismatch 572b's in it.  I have 
only used it on 40 & 20 so far. I get 500-550 watts output via 2 different 
watt meters (outboard of the SB 200). That requires a good tuning on my 
manual antenna tuner. I purchased new " matched" Chinese 572b's and still 
got about the same output. I am running the amp with 110 vac. I suspect I 
might do a slightly better output if I ran it with 220 vac, but dont have 
that available in the shack. My output check have been made in the cw mode 
with a solid key to do the tuning of the amp & ant tuner.

> Message: 3
> Date: Wed, 26 Jul 2006 15:46:49 -0700
> From: "Kenneth G. Gordon" <kgordon2006 at verizon.net>
> Subject: Re: [Heathkit] SB-200
> To: Heathkit at mailman.qth.net
> Message-ID: <44C78E69.11163.15A9521C at localhost>
> Content-Type: text/plain; charset=US-ASCII
>
> On 26 Jul 2006 at 18:22, w8qwl at juno.com wrote:
>
>> A lot of guys lie too!
>
> Or their meters do...or they look at them sideways...or...
>
> In any case, the SB-200 is a darned good little amp. According to the
> manual, it is rated at 1200 watts PEP input for SSB and 1000 watts
> input for CW at 50% duty cycle.
>
> If we assume 50% efficiency, CW power output would be 500 watts,
> and SSB PEP output would be 600 watts (but you would need a peak-
> reading watt meter to tell this with any reasonable accuracy).
>
> If we assume 65% efficiency, then those figures are 650 watts and 780
> watts PEP respectively.
>
> However, I don't know of any GG amps that run much more than 50%
> efficiency unless they were running push-pull Class B, and then the
> harmonic output and IMD is reportedly too high to be acceptable. (I
> don't know about this last bit, but so I have been told...)
>
> Now if we add in fed-through power from the driver, at 100 watts drive,
> something less than 50% of that power is fed through. But let us, for the
> sake of argument say that the 50% figure is acceptable.
>
> You can then add 50 watts to the above figures.
>
> In any case, 800 to 900 watts output with all parameters as originally
> set is not really possible, IMHO.
>
> But then again,  what do **I** know? :-)
>
> Ken W7EKB
>
>