[Heathkit] SB-200 10M Power Output

[Carl]

"What am I  missing here?"

Good tubes maybe. But I wouldnt expect that dramatic a drop between 20 
and 15M.

Start by putting the MFJ in a box in a dark closet. Then run the FT-450 
at 30-50W and align the coils properly.

Carl
KM1H



----- Original Message ----- 
From: "Tom Chesek" <tchesek at epix.net>
To: <heathkit at mailman.qth.net>
Sent: Wednesday, September 17, 2008 5:41 PM
Subject: Re: [Heathkit] SB-200 10M Power Output


>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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