[Lowfer] Question

[John Andrews]

Just a couple of thoughts on transmitting capacitors:

The capacitors with cast aluminum end plates and ceramic sides are actually
mica capacitors. They consist of a number of of caps in series and/or
parallel to give the required voltage and current ratings. Such caps are
frequently retired from service because they have changed value or developed
sufficient series resistance that they dissipate power and run "hot." The
value changes come from capacitor sections losing connection to the rest of
the bank. But they may also be taken out of service simply because new
tuning networks have been installed at a broadcast station. Such caps may be
perfectly good, and can be a bargain at flea markets.

The brown caps (such as those used by Mitch) are also micas. The same rules
apply as above, though with the lower current ratings they may have been
used in transmitters rather than in outside tuning networks. The stuff
outside is more susceptible to lightning damage.

In all cases, it would pay to check used capacitors for capacitance and
series resistance, particularly if you plan to run them near their ratings.
Your best weapon would be an RF impedance bridge.

John A.