> > 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
2.) What is the impedance seen at the base of the choke
referenced to chassis?
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.
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.
What major performance changes do you expect to see, if the 1/2
percent ripple is reduced from .5% to say .08 %? Or is this a "feel
better mod"? (Nothing wrong with that, as long as it doesn't hurt
anything else)
73, Tom W8JI
w8ji@contesting.com
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