On Wed, 29 Mar 2017 10:01:16 -0700, Jeff Liebermann
wrote:

Nope. That's an RF amplifier. I went looking for an RF probe
schematic based on a Nuvistor, but couldn't find anything. There are
some TEK oscilloscope front end circuits that use a Nuvistor, that
could probably be converted into something useful. Basically, one
needs a broadband impedance converter. Cascode (common emitter
driving a common base) design seems right. It would take two 6CW4
Nuvistors, a length of 3/4" copper pipe, and some high voltage. If
that's to messy, a single tube in a cathode follower derangement
should work. It might get warm enough to be uncomfortable, but that's
the price we pay for working with tubes.

Nuvistors are cheap on eBay but sockets are pricy:
http://www.ebay.com/sch/i.html?_nkw=nuvistor
Hmmm... LTSpice models available for various Nuvistors.
Never mind. I don't need yet another project.

For the record, I was ready to buy that kit from qrpkits.com, but found
out they do not recommend it for over 50V. I emailed the vendor and
asked if it could be upgraded for tube circuits. He told me that he can
not recommend that, because it could be a shock hazzard. Although I do
feel competent to make such a modification, I knew that would mean
spending more money, and wasting more time to build a usable probe.
Instead, I found a semi over priced old Eico RF probe (blue one) on
Ebay, and just paid the price. As soon as it comes, I'll be all set....

I never heard of using a nuvistor in a probe, but I am sure it's
possible. Seems kind of senseless though, when a simple diode along with
a few other parts will do the trick. Just because I prefer to work on
tubes, dont mean I wont use semi-conductors. For audio, tubes have a
superior sound. For my abilities and test gear, I'll take tubes any day
to work on. But I also do not mind working on older devices that contain
transistors, such as my XAM amp. It's the devices that contain IC chips
I detest. I'm not saying they are bad, and I am well aware my computer
and a lot of other stuff contain them. But I strongly dislike working on
that stuff. That was the main reason I stopped electronics in the late
70's as a hobby, and even more so as a repair business. It's not just
the fact that the stuff is very hard to work on, but also that parts are
far too hard to get.

As far as all thge political discussions that evolved in this thread, I
have no further comments. I hate politics. However, I know it all began
when I made a comment about todays youth being fat and lazy. That is my
opinion, and I see it all the time. Some of my very good friends have
kids who are now in their 20's and even their parents (my friends) say
the same thing. I see it all the time. That dont mean I am right, it's
just my opinion, buty I have a right to my opinion, and to express it
based on my "freedom of speech" as well as just saying what I feel. Then
again, there are a few exceptions. I know one young man who is a very
hard worker and he has a good head on his shoulders. But he is one in
100 or 1000. Most of today's youth have no goals. They spend their time
staring at their cellphones, work as little as possible (or not at all),
and eat as much as they can cram down their throats, and it shows!

However, none of that has anytrhing to do with the topic of this
newsgroup, aside from the fact that I would likely win a bet if I said
that no one on this group is under the age of 45. Today's youth dont
care to do electronics as a hobby. Nor do they care to do much of
anything that involves using their brains or muscles. But I am not gonna
join them. They can sit in their fancy restaurants and bars spending
their parents money, and talking on a cellphone to the person sitting
next to them. None of which makes any sense to me...... I'm just glad I
was born in the 50's when life still had meaning. My only complaint
about being born at that time is all the aches and pains I feel now!
Getting old sucks! But I doubt I need to explain that to any of you old
farts