[AMPS] Re: Ferrite Rod for 6M Amp

[Rich Measures]

>
>
>> All,
>> ?  the manufacturer. of 61 material rates it at 10MHz.  At 14MHz, I can
>> see waveform distortion on an oscilloscope.
>> Rich..."
>
>Rich "sees" many things no one else ever "sees" with their test 
>equipment.
>
€   In the test I performed with type-61 material operating at 14MHz, the 
slope of the waveform was noticably different from that of a sinewave -- 
esp. between 60-degrees to  80-degrees and 100-degrees to 130-degrees.   
.  My guess is that the distortion was >15%.  

>> Quoting from Amidon flyer: "Material 61  (u=125)  ..............Moderate
>> temperature stability and high 'Q' for frequencies 0.2mHz to 15mHz. 

€  Permag Pacific rates their u=125 material at 10MHz max. in tuned 
circuit apps.  .

>> Also commonly used for wideband transformers up to 200mHz."
>
>Quoting from Fair-rite Corp, an actual manufacturer of soft iron 
>materials, 61 material is suitable in broadband transformers and 
>EMI/RFI suppression devices up to 200 MHz, and tuned 
>applications up to 10 MHz. Q at ten MHz is 80.
>
€ The cathode of a g-g amplifier is akin to a tuned circuit. 

>61 Material is very common in broadband low distortion VHF 
>amplifiers, I used it in transformer designs for CATV and MATV 
>amplifiers...and multichannel video RF applications require very low 
>IM distortion. 
>
>> I would consider a filament choke to be in the latter category and if its
>> inductive reactance is the correct value, its impedance should be far
>> greater than that of the cathode and therefore not affect the waveshape a
>> significant amount.
>
>It wouldn't add appreciable harmonics anyway, unless core flux 
>density was high and frequency was low. 

>Upper frequency limit of 
>core material is set by eddy currents caused by the material having 
>large areas on non-insulated iron. At some frequency, the 
>permeability simply drops off and loss tangent slopes upwards. 
>
>That effect has NOTHING to do with waveshape distortion.
>
€  Harmonic distortion has everything to do with sine waveshape 
distortion.  

-  Cheers, Tom & Roy.  .


Rich...

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


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