Mike Andrews wrote:
Chuck Harris wrote:


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?


The problem I've encountered with switching supplies is that they're so
blasted noisy because of the fast risetimes in the high-current parts
of the supplies and because they're usually not very well shielded and/
or decoupled.

If you make it yourself, you can apply proper shielding and decoupling techniques.
It is done all the time in commercial radios. For a small receiver like is
being discussed here, the supply can be made in a couple of cubic inches...
Something that can be easily made in a soldered shut can with feedthru's on
all of the leads.

-Chuck

On Thu, 23 Jun 2005 10:58:02 -0400, Chuck Harris
wrote:

12V plate tubes are rather rare, perform poorly compared to most anything else.
They are very low power, low gain, and low frequency.

Philips produced a number of low-voltage tubes,such as the DAH50, A221 and A441,
in the '20s and '30s that people built successful radios with.
A few people have experimented in recent years with using normal tubes at
low voltages, try googling for "space-charge tubes".

--
Cheers,
Stan Barr stanb .at. dial .dot. pipex .dot. com
(Remove any digits from the addresses when mailing me.)

The future was never like this!

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.

Ed

Ed wrote:

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.

The QST Mobile Manual has a great project transceiver. The transmitter
is rockbound and based on a 1J6G tube, but it really gets out well. The
receiver I never built, but it didn't look like a bad design.

This thing WILL require a substantial B+... I think it needs a 67.V
battery. But you can put a few 9V radio batteries in series if you
really want.

Or you can build a vibrator supply. I think the Mobile Manual has an
article on vibrator designs as well.

The space-charge tubes are lousy... they worked well enough for cheap
car radios, but they never worked all that well. You can do a lot better
with a conventional tube design.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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

On 23 Jun 2005 18:07:27 GMT, Stan Barr wrote:
On Thu, 23 Jun 2005 10:58:02 -0400, Chuck Harris
wrote:

12V plate tubes are rather rare, perform poorly compared to most anything else.
They are very low power, low gain, and low frequency.

Philips produced a number of low-voltage tubes,such as the DAH50, A221 and A441,
in the '20s and '30s that people built successful radios with.
A few people have experimented in recent years with using normal tubes at
low voltages, try googling for "space-charge tubes".

See: http://www.duntemann.com/12vtubes/12vtubesindex.htm

--
Cheers,
Stan Barr stanb .at. dial .dot. pipex .dot. com
(Remove any digits from the addresses when mailing me.)

The future was never like this!

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.

During the 70s I did notice a lot of IC & FET failures in various
communications devices that were attributed to static electricty. I was
under the impression that the manufacturers had improved their designs
for that reason? On the other hand, doesn't really matter, I suppose,
since the end results help for both cases.

I'll probably continue my research on this project and start it this
Fall, if for no other reason than the fun of it. From what responses I'm
hearing to my original question, I'd be better off using conventional
tubes over the low voltage designs. I did want something that would
function off a 12V battery, though. We'll see....

My thanks to all.


Ed K7AAT

Has this link been posted yet?

http://www.duntemann.com/12vtubes/12vtubesindex.htm
--
Steven D. Swift, , http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA

(Steven Swift) wrote in news:da4r96$1rf$1
@eskinews.eskimo.com:


Has this link been posted yet?

http://www.duntemann.com/12vtubes/12vtubesindex.htm



Yes it has, but I appreciate your effort, anyway. Thanks.


Ed K7AAT

Behold, Steven Swift scribed on tube chassis:


Has this link been posted yet?

http://www.duntemann.com/12vtubes/12vtubesindex.htm

Cool, thanks!

I've been using 12V 300V SMPS.

--
Gregg "t3h g33k"
http://geek.scorpiorising.ca
*Ratings are for transistors, tubes have guidelines*