SB100,101 6hs6 sub and capacitors to correct "Miller" effect

[Ed Richards]

I just finished analyzing the circuit in question in a HW-101 (no
manual). please tell me if my analysis of the circuit is correct, if not
where did I go wrong?

In receive, I see +150 VDC being applied through a 100k resistor to the
diode anode, causing it to conduct and place the end of the 3.3 pf cap to
ground, placing it in parallel with the small section of the driver grid
tuning capacitor, increasing the total capacity by 3.3 pf.

In transmit, the +150 VDC is removed, allowing the -150 VDC bias to be
applied to the anode of the diode through a 1 megohm resistor, reverse
biasing it, effectively removing the 3.3 pf cap from the circuit.

What is the "Miller effect", and why does it occur? Why do you need 3.3
pf more capacity in receive? My education has obviously been
short-changed. Any response from you engineers out there will be
appreciated. Thank you.

Ed Richards

On Thu, 14 Sep 2000 22:27:50 -0400 Kenneth Bakhaus <bakken at MODEMPOOL.COM>
writes:
> Stu Lyon's mention of these changes in a recent posting tickled an
> old
> nerve. As I remember, I too just substituted the 6hs6 without any
> other
> mods. But on the "Miller" effect thing- Heath even had a
> modification kit,
> SBM-102-1, for the HW100, SB100, SB101, SB101W (don't remember this
> one)
> and some low number SB102s. I have the manual for the SBM-102 if
> anyone
> needs info- it is 8 pages long and since there is no copyright
> notice, it
> is probably ok to distribute (who's going to make anything off it
> now
> anyway but don't start a new thread on the copyright issue, been
> enough).
> The mod used two resistors, a disc cap and a diode.
>
> Ken Bakhaus, K8PAO since 59
>
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