On Tue, 28 Mar 2017 19:55:24 -0400, Michael Black wrote:

On Tue, 28 Mar 2017, analogdial wrote:

wrote:

Do any companies sell those blank RF probe tubes with metal tips? I
recall back in the 60s you could buy the entire probes with internal
parts as kits. They came with the same basic "shell" but had different
internal parts for different uses. The parts inside of them are basic.
Normally one diode and a resistor(s) or cap, or both.

I've found the schematics for several different probes, and I know that
some people build them in a pill bottle, or ink pen shell, or whatever,
but I'd like to find some of the REAL shells if they are sold.

Anyone know?

Thanks

The probe in the old ARRL handbooks was in the sort of shield and socket
used with 7 pin tubes. The pin connectors were removed from the socket
and a long screw was installed through the center tube of the socket.
All the RF probe parts were installed on a terminal strip which was held
to the socket by the screw which also served as the tip of the probe.


But it's no longer so easy to find tube sockets and shields. It looked
like a good idea back then.

But I did try making a probe, and I wasn't really pleased with the
results. It looked not so great.

I'd just go to a hobby store (they still exist) and hope to find some
brass tubing that was big enough and make probe case with that. If the
hobby store sells the brass tubing, then likely they sell small bits of
brass sheet, and one could make end caps with those.

For things that don't need shielding, old markers to work.

Michael

One of the kits linked in this thread, uses cpvc plumbing pipe, but they
cover it with adhesive copper foil. Thats a good idea. They have some
special caps on the ends, but I dont see why the pvc caps made for that
pipe would not work. Glue on the front one, leave the read one loose. or
put a little tape on it.

Copper plumbing pipe would make a good shell too, and the rear cap could
be a copper pipe cap with a rubber grommet drilled in (for the wire),
but I have not figured out what to use on the front that is
non-conductive, and still strong enough for the probe tip.

I was looking at some of the old Eico probes. I used to have some of
them (I wish I would have kept that stuff). There were 5 of them, all
color coded. Yellow was direct, blue was RF, Green was demodulator, red
was low capacity, and there was one more but I have not found pictures
of that one, or what it did.

Anyhow, I have a direct one, just coax with a regular probe on the
center lead and an aligator clip on the shield. But I want to make a RF
probe. I dont really see a need for a demodulator, or low capacity, but
I may in the future, now that I picked up a scope.