People here have recently mentioned tubes intended for portable
operation, with plate voltages of around 20 volts. Much more common are
tubes intended for running from mains-powered supplies. These mostly
require plate voltages that can be lethal. You should consider this when
designing kits for kids.

Roy Lewallen, W7EL

Bruce Kizerian wrote:
Thanks everyone for the interesting and useful information.

For the record, I am not particularly in love with tubes, but if there
is something they will do better than solid state devices I'm willing
to give it a try. When I can buy PN2222 bipolars for $.02ea and PN4416
JFETS two for a quarter, and dual gate MOSFETS for a nickel, the
expenditure for one of those fragile glass things better be well worth
it. It can' be different or just a little better. It has to be "knock
your socks off" superior...I make radio kits for kids and schools and
I want them to be able to afford the purchase.

Bruce kk7zz
www.elmerdude.com

In article ,
(Bruce Kizerian) writes:

Thanks everyone for the interesting and useful information.

For the record, I am not particularly in love with tubes, but if there
is something they will do better than solid state devices I'm willing
to give it a try. When I can buy PN2222 bipolars for $.02ea and PN4416
JFETS two for a quarter, and dual gate MOSFETS for a nickel, the
expenditure for one of those fragile glass things better be well worth
it. It can' be different or just a little better. It has to be "knock
your socks off" superior...I make radio kits for kids and schools and
I want them to be able to afford the purchase.

Here's something that might be fun to try on a regen or most any
other tuning circuit, a rebirth of the old reactance modulator circuit
to change the parallel capacity across a coil. For 190 KHz band-
width at about 6.1 MHz, this 3N200 dual-gate MOSFET add-on
claims linear-frequency tuning from a potentiometer. That's a bit
like the old "bandspread" tuning of prehistoric times. :-)

From EDN, 5 November 1998, Design Ideas Section, pp 130, 131,
Last idea entitled "Tube" Circuit Provides Linear Tuning. [came
across that one while searching for something else...]

On the Internet at http://www.reed-electronics.com/ednmag/archive/

Select year, then issue date in that year. A table of contents comes
up and scroll down to Design Ideas. Clicking on any Design Idea will
bring up the whole section in HTML. At the top of the HTML first
page is a box for a PDF of the same thing.

EDN has archives back to 1994 if anyone wants to peruse them or get
a copy of an older article.

Len Anderson
retired (from regular hours) electronic engineer person

In article ,
(Bruce Kizerian) writes:

Thanks everyone for the interesting and useful information.

For the record, I am not particularly in love with tubes, but if there
is something they will do better than solid state devices I'm willing
to give it a try. When I can buy PN2222 bipolars for $.02ea and PN4416
JFETS two for a quarter, and dual gate MOSFETS for a nickel, the
expenditure for one of those fragile glass things better be well worth
it. It can' be different or just a little better. It has to be "knock
your socks off" superior...I make radio kits for kids and schools and
I want them to be able to afford the purchase.

Here's something that might be fun to try on a regen or most any
other tuning circuit, a rebirth of the old reactance modulator circuit
to change the parallel capacity across a coil. For 190 KHz band-
width at about 6.1 MHz, this 3N200 dual-gate MOSFET add-on
claims linear-frequency tuning from a potentiometer. That's a bit
like the old "bandspread" tuning of prehistoric times. :-)

From EDN, 5 November 1998, Design Ideas Section, pp 130, 131,
Last idea entitled "Tube" Circuit Provides Linear Tuning. [came
across that one while searching for something else...]

On the Internet at http://www.reed-electronics.com/ednmag/archive/

Select year, then issue date in that year. A table of contents comes
up and scroll down to Design Ideas. Clicking on any Design Idea will
bring up the whole section in HTML. At the top of the HTML first
page is a box for a PDF of the same thing.

EDN has archives back to 1994 if anyone wants to peruse them or get
a copy of an older article.

Len Anderson
retired (from regular hours) electronic engineer person

Roy Lewallen wrote in message ...
People here have recently mentioned tubes intended for portable
operation, with plate voltages of around 20 volts. Much more common are
tubes intended for running from mains-powered supplies. These mostly
require plate voltages that can be lethal. You should consider this when
designing kits for kids.

Roy Lewallen, W7EL

That's is one of the reasons why a 9 volt battery is probably the
highest potential you will seen in my kits. The manuals I write are
full of precautions about soldering, erecting antennas, etc....but NO
high voltages...

But I still remember the jolt I got as a kid which caused me to drop a
heavy chassis on my toe...How did WE survive?

Bruce kk7zz
www.elmerdude.com

Roy Lewallen wrote in message ...
People here have recently mentioned tubes intended for portable
operation, with plate voltages of around 20 volts. Much more common are
tubes intended for running from mains-powered supplies. These mostly
require plate voltages that can be lethal. You should consider this when
designing kits for kids.

Roy Lewallen, W7EL

That's is one of the reasons why a 9 volt battery is probably the
highest potential you will seen in my kits. The manuals I write are
full of precautions about soldering, erecting antennas, etc....but NO
high voltages...

But I still remember the jolt I got as a kid which caused me to drop a
heavy chassis on my toe...How did WE survive?

Bruce kk7zz
www.elmerdude.com

On 19 Dec 2003 06:56:18 -0800, Bruce Kizerian wrote:

Roy Lewallen wrote in message ..
People here have recently mentioned tubes intended for portable
operation, with plate voltages of around 20 volts. Much more common are
tubes intended for running from mains-powered supplies. These mostly
require plate voltages that can be lethal. You should consider this when
designing kits for kids.

Roy Lewallen, W7EL

apart from the 6.3v heated types for car radio most such typers were
manufactured before 1930 and somewhat hard to find today, still the
WWII type RE074d is very rare

That's is one of the reasons why a 9 volt battery is probably the
highest potential you will seen in my kits. The manuals I write are
full of precautions about soldering, erecting antennas, etc....but NO
high voltages...

But I still remember the jolt I got as a kid which caused me to drop a
heavy chassis on my toe...How did WE survive?

I connected two 90V batteries in series and wasn't aware that the
headphone wasn't particularly insulated., still remember it very well
over 40 years later...

G3RZP mention the use of 6J7 as detector in his HRO, see Radcom nr
1/2004 page 45. It is described as combined AM/SSB detector, but I
wonder what sort of detector it is for AM. Is it grid or anode
detector? It is shown on http://home.online.no/~la8ak/17r.htm
Suppose it is still low level IF for AM - as for SSB.

On http://home.online.no/~la8ak/17s.htm I've shown the application of
a triode-hexode ACH1 which may be somewhat similar to 6K8, but here
the control grid is biassed with -4V and obviously operates as a
completely different AM-detector.

73
Jan-Martin
LA8AK
--
remove ,xnd to reply (Spam precaution!)

On 19 Dec 2003 06:56:18 -0800, Bruce Kizerian wrote:

Roy Lewallen wrote in message ..
People here have recently mentioned tubes intended for portable
operation, with plate voltages of around 20 volts. Much more common are
tubes intended for running from mains-powered supplies. These mostly
require plate voltages that can be lethal. You should consider this when
designing kits for kids.

Roy Lewallen, W7EL

apart from the 6.3v heated types for car radio most such typers were
manufactured before 1930 and somewhat hard to find today, still the
WWII type RE074d is very rare

That's is one of the reasons why a 9 volt battery is probably the
highest potential you will seen in my kits. The manuals I write are
full of precautions about soldering, erecting antennas, etc....but NO
high voltages...

But I still remember the jolt I got as a kid which caused me to drop a
heavy chassis on my toe...How did WE survive?

I connected two 90V batteries in series and wasn't aware that the
headphone wasn't particularly insulated., still remember it very well
over 40 years later...

G3RZP mention the use of 6J7 as detector in his HRO, see Radcom nr
1/2004 page 45. It is described as combined AM/SSB detector, but I
wonder what sort of detector it is for AM. Is it grid or anode
detector? It is shown on http://home.online.no/~la8ak/17r.htm
Suppose it is still low level IF for AM - as for SSB.

On http://home.online.no/~la8ak/17s.htm I've shown the application of
a triode-hexode ACH1 which may be somewhat similar to 6K8, but here
the control grid is biassed with -4V and obviously operates as a
completely different AM-detector.

73
Jan-Martin
LA8AK
--
remove ,xnd to reply (Spam precaution!)