> The biggest difficulty is making sure that the connection to the front of
> the vacuum variable capacitor is electrically good. I use an electrolytic
> capacitor clamp to hold the cap, and a piece of thin copper sheet under
> the clamp to make the connection. Because of inductance, this might not be
> too good at VHF though, and possibly I need to make a proper collett out
> of aluminium - or brass - for the new amp. However, in the antenna tuner
> for 160 and 80, there's no problem.
I use a sub-front panel and mount the capacitors directly to it. The
input and control circuits go between the sub-front and the front.
That way I can work on the input or control/bias/metering circuits
without any danger from having HV on and without disrupting airflow.
If I have occasion to use capacitors that aren't drilled and tapped on
the front, I bore an interference fit hole for the capacitor's front in a
small square of thick aluminum plate. I slot the plate from one side
of the hole out so I can use a long screw to squeeze the plate
against the capacitor.
I've never found any advantage to vertical mounting here in layouts,
but that probably because I use a sub-front panel.
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|