[Heathkit] How about the SB-220?

[Jim Shorney]

>Which goes against what the original designer recently said on another 
>forum.The original way had a 2-3dB IMD improvement which is identical to 
>what Ive measured as far back as the early 80's with the SB-220.

I'm not sure exactly what part of the below that you are commenting on here,
Carl.

73

-Jim



On Sun, 23 Aug 2009 11:29:12 -0400, Carl wrote:

>
>----- Original Message ----- 
>From: "Jim Shorney" <jshorney at inebraska.com>
>To: <heathkit at mailman.qth.net>
>Sent: Saturday, August 22, 2009 3:37 PM
>Subject: Re: [Heathkit] How about the SB-220?
>
>
>> On Sat, 22 Aug 2009 12:32:27 -0700, Paul Baldock wrote:
>>
>>>I'm not sure this is true. I have rebuilt two SB221's and grounded
>>>the grids directly. This does give more gain and allows you to turn
>>>the driver rig down. Turning the driver down from 100W to 90W on a
>>>12V rig greatly improves its IMD and more than the negative feed back
>>>that the amp "may" have with the Heathkit design.
>>>
>>>I have had no instability problems and the output is very clean. I'm
>>>not aware of any modern 2 X 3-500Z amps that use the Heathkit method,
>>>they all directly ground the grids.
>>
>>
>> After reading all the pros and cons of this idea, I came to the conclusion 
>> that
>> the reasons for directly grounding the grids made more sense (to me) than 
>> the
>> alternatives. I grounded the grids in my L-7 and it has been running great 
>> that
>> way. FWIW.
>
>Which goes against what the original designer recently said on another 
>forum.The original way had a 2-3dB IMD improvement which is identical to 
>what Ive measured as far back as the early 80's with the SB-220.
>
>Carl
>KM1H
>
>
>>
>> 73
>>
>> -Jim
>>
>>
>> --
>> Ham Radio NU0C
>> Lincoln, Nebraska, U.S.S.A.
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>>
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>>
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>>
>>
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--
Ham Radio NU0C
Lincoln, Nebraska, U.S.S.A.
TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time!

"Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime."

HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/
http://radiojim.exofire.net
http://incolor.inetnebr.com/jshorney
http://www.nebraskaghosts.org