[AMPS] Re: Ferrite Rod for 6M Amp

[Rich Measures]

>
>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.
>
€  agreed

>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 

€  I did not say that I saw intermodulation distortion.   I saw harnonic 
distortion of the sine wave.  The signal was 100w of A-Ø/dead carrier.  

>because the cores he claims are "no good" 
"
€  I did not say that type-61 ferrite core material is "no good.  I 
essentially said that the manufacturer's rating of 10MHz should not be 
casually ignored.  Just because type-61 RF attenuator beads are rated for 
200MHz max,  does this mean type-61 ferrite is going to work OK every 
time in the tuned cathode input of a 6m amplifier?.  
> 
>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. 

€  remove >15% harmonic distortion, Tom?  
My fix was to switch from type-61 (Mu=125/10MHz) ferrite core material to 
a core material that was rated at 50MHz/Mu=40, and add a few turns.  

"I know that most men, including those who are at ease with problems of 
the greatest complexity, can seldom accept even the simplest and most 
obvious truth if it be such as would oblige them to admit the falsity of 
conclusions which they had delighted in explaining to colleagues, which 
they had proudly taught to others, and which they had woven, thread by 
thread, into the fabric of their lives."  ­ L. Tolstoy, UA9LEV

-  Cheers, Tom.  




Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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