Ed wrote:
SNIPPED

Is there a particular reason that you want to use this style of tube?

Today it is trivial to make a simple switching power supply that can
provide a couple of hundred volts at 98% efficiency, why not make one
of them, and use some real tubes?

-Chuck



OK, good info in your reply, Chuck. My reply to your question (above)
will probably elicit a whole lot of comments. I hope they're not too
negative! HI HI

I am recently retired, and am about to have some extra time on my
hands for some construction projects. With the re-surfacing of an old
news item about terrorists or certain nations who may attempt to launch a
nuclear EMP strike on this country, I was thinking about an old project I
had once wished to start many years ago; That is an EMP proof ham rig
for 75/40 .... probably CW only, for simplicity sake.

So I'm thinking of building a fairly simple tube rig, preferably
superhet Rx, with tubes that will run totally on a 12V supply. Assuming
that we never have such a terrible thing happen to us, a rig like this
would still be fun to use. Following the building of a Rx, I'll probably
build a simple one tube TX to match.

Hi Ed,

I would put the probability of experiencing EMP in our life times at
somewhere around zero, but that isn't a good reason not to proceed down
the path you are intending to travel.

The IC manufacturers suffered a wakeup call back in the 70s when things
were pretty hot with the cold war. It became a commonly held belief that
virtually all of the electronic devices in the country would fail when faced
with a nuclear attack. So, a hustle was begun to harden all of the IC's
against EMP. It turned out to be pretty easy to do. All they did was
redesign the pads, which are specialized circuits that connect to the outside
world, so that they could safely absorb the EMP. It had a beneficial effect on
static electricity survival too! So, if you do a good job of keeping the
EMP from coupling in through large antennas, power connections, etc. The
IC's pads should be able to do the rest. Power FET's are similarily protected,
so they should be a good bet in an environment where EMP is a possibility.

If you are planning to make a transmitter too, you are going to find that
the 12V tubes aren't much help. There are a couple that are called "Power
amplifier" tubes. Despite their encouraging name, they were not designed
to provide more than about 20 milliwatts. Their purpose was to go between
the detector/preamplifier tube, and the DS501 power transistor that was
used to drive the speaker.

As to designing with the 12V tubes, that shouldn't be a big problem, they
behave very similarily to normal tubes. The big issues are high plate
resistances, low gains, and low power levels. There is a group of antique
military radio collectors that want to play with their radios, but don't
want to recap, or permanently modificy the radios in any way. They have
done extensive experimentation with running military receivers with plate
voltages down around 28V. Their reasoning is that even the worst electrolytic
will still perform OK at 1/10th of its normal operating voltage. The
radios play...weakly.. but they play.

-Chuck