Source for RF "pass-through"?
 

Could it be a feed through capacitor? This is a short from one side of the
wall to the other, but it has some capacitance to ground. The purpose it to
pass DC but shunt high frequencies to ground. Very useful for passing DC
power supply voltages through a chassis wall. A picture and price are he

http://www.oselectronics.com/ose_p95.htm

Al KA5JGV



"DaveC" wrote in message
al.net...
Not sure of the proper name, but I'm looking for a connector that provides
connection through a bulkhead, from one PBC to another PCB. Not a
"connector"
in the traditional sense. Both sides of it look like the back end of a
solder-type connector; just someplace to solder a wire.

I've searched Digi-Key, Mouser, and a few others, but can't find anything
like this. I've seen them in hi-f comm equipment.

I need one for 2.4 GHz.

Where can I find one?

Thanks,
--
DaveC

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I guess that won't do for my purpose. I'm trying to do just the opposite:
preserve the RF while passing it through a hole in the shielding. It only
has
to span about 3/4 of an inch (17mm?). What's the best device for this
purpose?

17 mm of coax. RF doesn't like to go thru little holes.

W4ZCB

17 mm of coax. RF doesn't like to go thru little holes.

OK, coax it is. Can I use coax without the outer poly jacket? It would make
it much easer to solder in that small space if it were not there.

It can be used without the outer insulation, as long as you make sure
that the braid doesn't accidentally touch anything which isn't
supposed to be part of the RF ground.

In fact, if you're using coax to create a feed-through into a
shielded, grounded subenclosure (e.g. one made out of scrap PCB
material soldered to the main board's ground plane) then it would
probably be a very good idea to remove the outer insulation, feed the
coax through a hole in the enclosure wall which is just _barely_ big
enough, solder the ends into place, ground both ends of the braid, and
then also solder the braid to the subenclosure wall where it passes
through.

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.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

By the way... They used to also make feed through thingies that didn't include
capacitance. But a 3/4 inch wall would exceed their capability.

Oh, and at 2.4 Gigs, 17 mm of coax will look like a transmission line.

Bill, K5BY

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
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!