[Heathkit] SB-200 10M Power Output

[Tom Chesek]

I saw this message thread a few days ago and it got my interest. My SB-200 
has full power out (550-600W) on 84/40/20 with 100W input but on 15/10 both 
will only do around 160W out with 100W in. I've made sure that all 
connections are tight. I've cleaned the bandswich and verified that there is 
good wiping action on each contact. I've used my MFJ-259B to check/set the 
SWR on the input coils with power on and the relay energized and have an swr 
of around 1.7 on 15 meters and 1.7 in the middle of the 10 meter band. These 
readings are confirmed by my Yaesu FT-450 built in SWR meter. What am I 
missing here?

Tom K3TVC



----- Original Message ----- 
From: "Glen Zook" <gzook at yahoo.com>
To: <heathkit at mailman.qth.net>; "Mark K3MSB" <mark.k3msb at gmail.com>
Sent: Sunday, September 14, 2008 4:01 PM
Subject: Re: [Heathkit] SB-200 10M Power Output


> The tubes might be a little soft.  However, you are not going to get much 
> over 450 watts output on 10 meters especially with that kind of drive. 
> Maybe 500 watts or a little more with brand new tubes and 100 watts drive.
>
> Remember, the SB-200 was designed for around 100 watts drive and the 
> efficiency drops off on 10 meters.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Sun, 9/14/08, Mark K3MSB <mark.k3msb at gmail.com> wrote:
>
> From: Mark K3MSB <mark.k3msb at gmail.com>
>
> I'm getting between 550 and 600W out (CW) on 80-20, 500W on 15,  and
>> between 300 and 400 on 10M. I'm trying to figure out if there's anything 
>> I can do to increase the output power on 10M.  Here's what I've measured:
>
> 28.0:   350-400W.   (75W drive, 1.5:1)
> 28.4:   300W          (75W drive, 1.5:1)
> 29.0:   300W          (50W drive, 2.1:1 )
>
> For reference:
>
> 14.2:  600W  (60W, 1.2:1)
>
> The figures in parenthesis are the drive from my 756P3 and the SWR 
> indication between 756 and linear.
>
> I initially thought to adjust L1 to bring down the SWR for a better tuned 
> input match for the phone band.  However, after looking at what I'm 
> getting on the low end of 10 (good SWR) and the mid and higher parts of 
> 10M (mediorce SWR),  I don't think it's worth it to muck with L1 to get 
> another 50 to 100W of output power.    I'm getting plenty of drive as it 
> is.
>
> The tubes are not new, and I've had to replace just about every resistor 
> in the beastie.   I'm thinking the tubes are just soft.
>
>
>
>


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