>
>Tom and Rich,
>
>This whole discussion makes no sense to me.
? It was not me who added the subject of IMD.
> If I put two sinewaves into
>any kind of nonlinear network, I would expect to see IMD products as well as
harmonics
>results.
? Would one be able to see IMD products on an oscilloscope connected
across the resistive termination for the RF signal?
- cheers, Mike.
>After passing thru the non-linearity, the two sine waves will no longer be
>linearly
>independent - in essence the two signals should begin to cross modulate
>each other.
>
>Please elaborate - thanks!
>
>
>73 de Mike, W4EF........................
>
>
>
>-----Original Message-----
>From: Tom Rauch [SMTP:w8ji@contesting.com]
>Sent: Saturday, May 29, 1999 3:49 AM
>To: 'AMPS'; Gilmer, Mike
>Subject: RE: [AMPS] Re: Ferrite Rod for 6M Amp
>
>
>Hi Mike,
>
>> > >People who aren't totally familiar with PA operation sometimes
>> > >confuse harmonic distortion with the type of distortion that causes
>> > >splatter. Splatter is NOT caused by harmonic distortion, splatter is
>> > >caused by amplitude non-linearity in the envelope shape.
>>
>> Is not amplitude non-linearity in the envelope of the RF actually
>> (usually?) harmonic distortion in the AUDIO? This is splatter, right?
>> Perhaps two-tone type stuff in the not-so-linear (on purpose or otherwise)
>> parts of the transmitter can contribute, too, but the audio is where we
>> tend to create splatter.
>
>Absolutely not!! That's a common misconception, but totally untrue.
>
>Call the distortion by the proper name, and you will see why it is
>true. Harmonic distortion, the RF distortion that occurs at a
>fractional RF-cycle rate, only produces even-order products of the
>original signal(s). If I had a transmitter on 7.0 MHz, the closest
>harmonic distortion product would be on 14 MHz. That would be
>true even if it was multi-tone modulation.
>
>If the same transmitter was modulated by a two-tone signal, but
>had envelope amplitude non-linearity, it could produce what we call
>"splatter" or IMD products.
>
>Now, I don't believe for a second Rich measured what he "claims"
>to have measured because the cores he claims are "no good" are
>used in hundreds or thousands of broad band applications where
>harmonic distortion would be absolutely intolerable (multi-band
>CATV applications and other broadband amplifiers, harmonic
>suppression, etc) but even if he did measure fraction RF-cycle
>distortion it wouldn't mean a thing for filtered RF amplifiers. The
>output filters would remove virtually every trace of harmonic
>distortion.
>
>If that wasn't true, we couldn't use class AB or B single ended PA's
>in amplifiers...and push-pull RF amps would be cleaner for IMD
>than single ended amps....and that certainly is not true.
>
>
>> > >> ? Harmonic distortion has everything to do with sine waveshape
>> > >> distortion.
>> > >
>> > >That's right. But harmonic distortion has no ill effects in a narrow
>> > >band PA.
>> > >
>> > It does when your neighbors are watching the NBA playoffs.
>> >
>>
>> Harmonics content in the RF are not and do not cause "splatter".
>>
>> However, harmonics of the RF do make it out the connector (albeit
>> 30-40dB down) and into the antenna and get radiated, even though the PA
>> and the antenna are "narrow-band".
>
>What a poor PA you have! It doesn't even pass FCC requirements
>beyond a hundred watts or so output! Not only that, the tube
>generates harmonics that are much worse than any other
>components, and you seem to follow (swallow?) the argument that
>a filament choke carrying a ting bit of magnetization from drive
>power would be a problem in a system where the tube itself only
>conducts for a fraction of a cycle?
>
>
>
>73, Tom W8JI
>w8ji@contesting.com
>
>--
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>
>--
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>
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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