At 10:33 PM 11/5/2004, Will Matney wrote:
<snip>
Well, the DC currents and RF currents are intermixed in the chassis
itself. The RF current circulates through the tank circuit to the load and
back to ground. It is also across the cathode and anode of the tube(s).
The reason for mentioning the PSU ground is the B- is at the cathode. But,
the tank capacitors and coil charge and discharge through the load and
then back. The power fed to the tank then is created by the tube(s) and
PSU. By the impedances being different, more RF should go to ground
through the wipers than through the shaft. Actually, that's how they're
designed to operate. It's really a simple parallel resistor circuit but
with mighty low resistances.
Since a part of tuning capacitance is the internal capacitance of the
tube, the best possible scenario would be to have both the tune and load
cap frames or wipers going to a _single point_ ground at the tube RF
ground location.
Exactly, and with the shortest connection possible.
Those circulating RF currents should not pass through the negative lead
of the power supply at all.
No they wont, they are blocked by the plate choke from doing so, and
filtered by the bypass capacitors. They intermix with each other through
the chassis only at the tube(s).
<snip>
I have to ask... with all the talk about the combined currents on the
chassis... call that common... signal ground... chassis ground... ground or
take your pick... no one has said anything about skin effect...
resistance, especially on the surface (where your RF is) of aluminum. What
are you doing about that? Are you treating your aluminum chassis with
chromate?
73, Tony W4ZT
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