In article et,
DaveC wrote:

A more standardized way of creating such RF feedthroughs is to mount
an SMA connector on the subenclosure wall - solder minicoax to one
side of it (often the inside), and use a flexible or mini-hardline
coax with an SMA plug to connect to the other side.

So make a male-female connection?

Right. Mount a female SMA jack on/through the wall (solder it, for
best shielding and grounding), connect coax to its rear connector
inside the subenclosure, and use a male SMA on the cable which
connects to it on the outside.

I'm trying to preserve as much of the
signal as possible. This will lose a few dB, won't it?

Great Ghu, I should certainly hope not! Unless you create a really
severe impedance mismatch when you connect the coax, almost all of the
power will get through without being either reflected or absorbed.
You shouldn't lose more than a very small fraction of 1 dB if you do
it right.

This sort of hookup approach appears widely throughout the excellent
"Experimental Methods in RF Design" book by W7ZOI/KK7B/W7PUA,
available through the ARRL. In this book it's quite common to see
modules such as local oscillators and bandpass filters being
constructed inside sealed enclosures, with the power going in via the
capacitive feedthroughs someone else mentioned, and signals going in
and out on SMA connectors (or BNC if you've got the space and want to
save a few bucks).

You'll also see this approach used in commercial microwave gear.

--
Dave Platt AE6EO
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