[AMPS] a sticky issue.

[measures]

>
>> > Indeed.  At the other end of the spectrum we find a 1000pF  "bypass" on
>> > the anode supply.  At 1.8MHz, 1000pF has 88-ohms of Xc.   It is my
>> > opinion that this does not represent good engineering practice.  By
>> > comparison, at the lowest frequency of operation, the SB-220 has a
>> > 20-ohm
>> 
>> Were I running a string of electrolytic filter caps on a 160 meter amp, I
>> would want a total of .01 mfd bypass capacitance at the base of the plate
>> choke.
>> 
>> I found that even on the Alpha 77 series that 160 meter RF is abundant all
>> the way back to the line cord if additional bypassing is not done. The B&W
>> 800 choke is not too swift on "Top-Band."
>> 
>> (((73)))
>> Phil, K5PC
>
>Hi Phil,
>
>I have three questions:
>
>1.) What is the impedance of the choke in the AL-1500
>
The L of  RFC-3 is not stated in the AL-1500's parts list. 

>2.) What is the impedance seen at the base of the choke 
>referenced to chassis?
>
Depends on the C of the bypass capacitor.  My guess is that roughly 
0.8A-rms passes through RFC-3 at 1.8MHz.  

>3.) What difference do you expect to see?
>
>You must have the answers, or you wouldn't be able to make a 
>determination of bypass requirements.
>
Your method of determination appears to be flawed.  

>In my determination, the ripple in the supply at 1.8 MHz is about 
>1/2 of a percent when actual impedances are considered. Hardly 
>enough to worry about. 
>
Adrift in a sea of misunderstanding.  // RF voltage on electrolytic 
filter caps is the main concern. 

>What major performance changes do you expect to see, if the 1/2 
>percent ripple is reduced from .5% to say .08 %? 

The HV RF bypass cap Has Nothing to do with ripple, Tom. 

> Or is this a "feel 
>better mod"? (Nothing wrong with that, as long as it doesn't hurt 
>anything else)
>
....  clueless  

end

-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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