[Amps] T networks and harmonics

[R.Measures]

When used with a halfwave dipole and antenna tuner, my SB-220 has a 
second harmonic level of c. 60db down.

On Feb 6, 2006, at 4:17 PM, carl s. wrote:

>    In reply to all this discussion, !! How , and /or where does Our
>   Wonderful FCC , expect the "average" Ham to "buy and or borrow" the 
> the
> required "expertise and/or equipment to check all this output 
> stuff.????
>     In all my years I've never had anyone complain about my signal
>    quality, be it am, fm, ssb, or any other. I had one msg. from an
>    OO way back in the late 50's or so, when I got a report of 2nd 
> harmonic
> on 40 mtrs. when I was on 80 , mtrs.But that's not quite the same thing
> today.!!! (that was on CW )
>     Oh, well !!!!
>      Just my two cents worth.!!!!
>     carl / kz5ca
> ----- Original Message -----
> From: "Jim Kearman" <jkearman at att.net>
> To: "Amps" <amps at contesting.com>
> Sent: Monday, February 06, 2006 7:04 PM
> Subject: Re: [Amps] T networks and harmonics
>
>
>> From: "Gary Schafer" <garyschafer at comcast.net>
>>
>>> I guess this was in response to your response to someone that said 
>>> that
> "a T
>>> network tuner after the amp would not help reduce harmonics as it was
>>> basically a high pass filter". You said that "it would help some".
>>
>> Of course, this is beyond the scope of my original post about the 
>> need for
> pi-L output tanks to meet current FCC requirements, but thanks for the
> backup. The Regs require spurious emissions be below a certain level 
> _at the
> output of the transmitter_, which would imply the output of the 
> amplifier
> used in conjunction with a transmitter or transceiver. Not the output 
> of the
> antenna tuner unless it is integrated into the amp/transmitter.
>>
>> Also, while a T-network _may_ attenuate harmonics sufficiently so 
>> that the
> total system meets the spirit of the Regs, it's hard to know the 
> effect of
> any combination of antenna and tuner settings. If the second harmonic 
> at the
> amp output is -35 dB and the tuner adds another 8 dB, you have the -43 
> dB
> required by the Regs, though not in the right place. Yes, I doubt FCC 
> is
> going to come knocking, but we want to build according to the best 
> Amateur
> standards.
>>
>> So I think we can draw two conclusions: A pi network is inadequate, 
>> and a
> t-network antenna tuner is neither a legal nor a necessarily adequate
> solution.
>>
>> In case the Commission is reading this, I assure them my pi-net 
>> amplifier
> was "installed" prior to 1978!
>>
>> 73,
>>
>> Jim, KR1S
>> http://kr1s.kearman.com/
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>
>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org