Remote Cutoff Pentodes in Regens
 

I have seen remote cutoff pentodes such as the 1T4 used in
regenerative receivers. I'm guessing there is a good reason...perhaps
something to do with the decrease in gain with increasing signal
level...so that the pentode oscillator "fights" going into to
oscillation enough to give a very smooth transistion...rather than the
more abrupt transistion of some solid state circuits.

I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

And speaking of the 1T4...has anyone played with these enough to give
me some ideas for using them in regenerative radios. I also wondering
how much you can starve the plate and still get good results in a
regen receiver.

Thanks

Bruce Kizerian
www.elmerdude.com

In article ,
(Bruce Kizerian) writes:

I have seen remote cutoff pentodes such as the 1T4 used in
regenerative receivers. I'm guessing there is a good reason...perhaps
something to do with the decrease in gain with increasing signal
level...so that the pentode oscillator "fights" going into to
oscillation enough to give a very smooth transistion...rather than the
more abrupt transistion of some solid state circuits.

A 1T4 is an old directly-heated cathode tube. Played with those
a 56 years ago...in regenerative receivers...:-)

Looking back at those old magazine article projects, I'd surmise
that the "reason" a particular tube was used was that it was
AVAILABLE to use.

A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?" If you bias the control grid of a 1T4 about all you
will do is change the feedback setting for that hairy transition just
prior to going into self-oscillation.

And speaking of the 1T4...has anyone played with these enough to give
me some ideas for using them in regenerative radios.

The last time I played with battery-filament tubes (including the 1T4)
was in helping a friend restore an AN/PRC-8 Korean War era walkie-
talkie in the 70s (I wore one once in 1953). Nice VHF FM transceiver
very stable. The first time I played with a 1T4 was in a regenerative
receiver back in 1947 and it was very touchy on feedback setting
versus frequency on MF to HF bands (plug-in coil thing).

I also wondering
how much you can starve the plate and still get good results in a
regen receiver.

Experiment with it. There's not a large amount of data on regenerative
receivers any more and very little in the way of vacuum tube info.
A 1T4 power demand is minimal, 1.5 VDC filament at 50 mA and about
2.4 mA plate and screen current at 45 VDC supply. [183 mW total
supply drain] That's fairly "starved" considering the transconductance
is only 700 umhos (typ) at 0 VDC control grid. Even at "maximums"
of 90 V plate and 67 V on screen, the transconductance is only 900
umho.

A 1L4 is a close cousin to the 1T4 as a sharp-cutoff pentode, same
envelope, filament, etc., but the gm is about ten percent higher. A
3Q4 or 3S4 (a 1S4 was made but was not recommended for new
designs back in 1956) has a gm of 1500 umho at twice the filament
voltage and 8.8 mA plate+screen at 90/67 V. Those "power pentodes"
have a semi-remote-cutoff characteristic. [800 mW power supply
demand would be "power" from a battery pack way back then...]

Regenerative receivers were all the rage among hobbyists back
about 1930 when tubes were relatively expensive and lacked
transconductance for effective RF amplification. Such were a
cheap way to get more sensitivity out of a single tube stage...but at
the expensive of instability and lack of uniform selectivity. Once the
superheterodyne was into production, it proved far better overall.

For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

Len Anderson
retired (from regular hours) electronic engineer person

In article ,
(Bruce Kizerian) writes:

I have seen remote cutoff pentodes such as the 1T4 used in
regenerative receivers. I'm guessing there is a good reason...perhaps
something to do with the decrease in gain with increasing signal
level...so that the pentode oscillator "fights" going into to
oscillation enough to give a very smooth transistion...rather than the
more abrupt transistion of some solid state circuits.

A 1T4 is an old directly-heated cathode tube. Played with those
a 56 years ago...in regenerative receivers...:-)

Looking back at those old magazine article projects, I'd surmise
that the "reason" a particular tube was used was that it was
AVAILABLE to use.

A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?" If you bias the control grid of a 1T4 about all you
will do is change the feedback setting for that hairy transition just
prior to going into self-oscillation.

And speaking of the 1T4...has anyone played with these enough to give
me some ideas for using them in regenerative radios.

The last time I played with battery-filament tubes (including the 1T4)
was in helping a friend restore an AN/PRC-8 Korean War era walkie-
talkie in the 70s (I wore one once in 1953). Nice VHF FM transceiver
very stable. The first time I played with a 1T4 was in a regenerative
receiver back in 1947 and it was very touchy on feedback setting
versus frequency on MF to HF bands (plug-in coil thing).

I also wondering
how much you can starve the plate and still get good results in a
regen receiver.

Experiment with it. There's not a large amount of data on regenerative
receivers any more and very little in the way of vacuum tube info.
A 1T4 power demand is minimal, 1.5 VDC filament at 50 mA and about
2.4 mA plate and screen current at 45 VDC supply. [183 mW total
supply drain] That's fairly "starved" considering the transconductance
is only 700 umhos (typ) at 0 VDC control grid. Even at "maximums"
of 90 V plate and 67 V on screen, the transconductance is only 900
umho.

A 1L4 is a close cousin to the 1T4 as a sharp-cutoff pentode, same
envelope, filament, etc., but the gm is about ten percent higher. A
3Q4 or 3S4 (a 1S4 was made but was not recommended for new
designs back in 1956) has a gm of 1500 umho at twice the filament
voltage and 8.8 mA plate+screen at 90/67 V. Those "power pentodes"
have a semi-remote-cutoff characteristic. [800 mW power supply
demand would be "power" from a battery pack way back then...]

Regenerative receivers were all the rage among hobbyists back
about 1930 when tubes were relatively expensive and lacked
transconductance for effective RF amplification. Such were a
cheap way to get more sensitivity out of a single tube stage...but at
the expensive of instability and lack of uniform selectivity. Once the
superheterodyne was into production, it proved far better overall.

For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

Len Anderson
retired (from regular hours) electronic engineer person

A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?"

Here, I was speaking in more general terms and not referring to
regenerative circuits.



Experiment with it.

I plan on it.


For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

The voltage gain of an effective regenerative stage is can be as high
as 100,000 as reported by Charles Kitchin. That's 100dB...not many op
amps have that kind of gain at say 10MHz.

Thanks for your comments. I always appreciate hearing from folks with
lots of valuable radio experience to share.

Bruce kk7zz
www.elmerdude.com

A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?"

Here, I was speaking in more general terms and not referring to
regenerative circuits.



Experiment with it.

I plan on it.


For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

The voltage gain of an effective regenerative stage is can be as high
as 100,000 as reported by Charles Kitchin. That's 100dB...not many op
amps have that kind of gain at say 10MHz.

Thanks for your comments. I always appreciate hearing from folks with
lots of valuable radio experience to share.

Bruce kk7zz
www.elmerdude.com

In article ,
(Bruce Kizerian) writes:

A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?"

Here, I was speaking in more general terms and not referring to
regenerative circuits.

If you are speaking in general terms then there are plenty of gain-
control elements out there. For a single-IC type of device, the
old Motorola MC1350 (8-pin DIP) is a sort-of Gilbert Cell arrangement
inside, differential-in, differntial-out, constant parallel Z-in of 5 KOhm
in parallel with a couple pFd each input. The gain control portion is
done by "starving" or actually redirecting the DC emitter current in the
input differential pair. Jameco (www.jameco.com) still sells this IC
at around $1.20 (?) in singles and has a copy of the Motorola data
for download on their website. That datasheet has a schematic of the
insides. That's good up into mid-VHF.

Some of the older JFETs had non-linear source-drain curves v. gate
voltage curves...see the difference in biasing for "depletion" and
"enhancement" mode operation. I don't know if they will work to
the top of HF range, though.


For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

The voltage gain of an effective regenerative stage is can be as high
as 100,000 as reported by Charles Kitchin. That's 100dB...not many op
amps have that kind of gain at say 10MHz.

I was suggesting using op-amp ICs WITH positive feedback. :-)

I'm just not going to buy "100 db voltage gain" in a regen based on
my own experiences...unless I see the bench layout and check the
calibration stickers on the test equipment determining this. :-)

Frankly, to get a simple receiver for HF, the Tayloe Mixer and its
separate LO followed by a low-noise AF range op-amp has the
most sensitivity for the fewest parts...and with little possibility of
re-radiating the oscillations of a regenerative due to a twitch of the
regeneration control. As a direct-conversion receiver, it can handle
CW or SSB and, with a stable LO, can take in conventional AM
with a lot less tweaking than a regen with a touchy regen control.

The most stable regen I ever built (three in all, the first using that
1T4) was with a 117N7 beam-power pentode and rectifier diode, AF
out driving an old, old high-impedance dynamic speaker. Plate curves
of that tube were of the sharp-cutoff variety. AM BC band, not much
else to listen to for entertainment in 1948. I suspect it was acting
more like a "plate detector" but it had the sensitivity of a common
"all-American-five" AM table top radio receiver.

Some of the minimal-tube-complement receiver designs of older times
used regenerative detectors at the IF for sensitivity improvement. I
know of one old Hallicrafters S-38 (?) reworked that way. That receiver
had essentially an "all-American-five" tube lineup and no power
transformer. Somewhat unsafe, but useable.

Nostalgia isn't what it used to be...

Len Anderson
retired (from regular hours) electronic engineer person

In article ,
(Bruce Kizerian) writes:

A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?"

Here, I was speaking in more general terms and not referring to
regenerative circuits.

If you are speaking in general terms then there are plenty of gain-
control elements out there. For a single-IC type of device, the
old Motorola MC1350 (8-pin DIP) is a sort-of Gilbert Cell arrangement
inside, differential-in, differntial-out, constant parallel Z-in of 5 KOhm
in parallel with a couple pFd each input. The gain control portion is
done by "starving" or actually redirecting the DC emitter current in the
input differential pair. Jameco (www.jameco.com) still sells this IC
at around $1.20 (?) in singles and has a copy of the Motorola data
for download on their website. That datasheet has a schematic of the
insides. That's good up into mid-VHF.

Some of the older JFETs had non-linear source-drain curves v. gate
voltage curves...see the difference in biasing for "depletion" and
"enhancement" mode operation. I don't know if they will work to
the top of HF range, though.


For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

The voltage gain of an effective regenerative stage is can be as high
as 100,000 as reported by Charles Kitchin. That's 100dB...not many op
amps have that kind of gain at say 10MHz.

I was suggesting using op-amp ICs WITH positive feedback. :-)

I'm just not going to buy "100 db voltage gain" in a regen based on
my own experiences...unless I see the bench layout and check the
calibration stickers on the test equipment determining this. :-)

Frankly, to get a simple receiver for HF, the Tayloe Mixer and its
separate LO followed by a low-noise AF range op-amp has the
most sensitivity for the fewest parts...and with little possibility of
re-radiating the oscillations of a regenerative due to a twitch of the
regeneration control. As a direct-conversion receiver, it can handle
CW or SSB and, with a stable LO, can take in conventional AM
with a lot less tweaking than a regen with a touchy regen control.

The most stable regen I ever built (three in all, the first using that
1T4) was with a 117N7 beam-power pentode and rectifier diode, AF
out driving an old, old high-impedance dynamic speaker. Plate curves
of that tube were of the sharp-cutoff variety. AM BC band, not much
else to listen to for entertainment in 1948. I suspect it was acting
more like a "plate detector" but it had the sensitivity of a common
"all-American-five" AM table top radio receiver.

Some of the minimal-tube-complement receiver designs of older times
used regenerative detectors at the IF for sensitivity improvement. I
know of one old Hallicrafters S-38 (?) reworked that way. That receiver
had essentially an "all-American-five" tube lineup and no power
transformer. Somewhat unsafe, but useable.

Nostalgia isn't what it used to be...

Len Anderson
retired (from regular hours) electronic engineer person

Avery Fineman wrote:
In article ,
(Bruce Kizerian) writes:


A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.


I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?"

Here, I was speaking in more general terms and not referring to
regenerative circuits.


If you are speaking in general terms then there are plenty of gain-
control elements out there. For a single-IC type of device, the
old Motorola MC1350 (8-pin DIP) is a sort-of Gilbert Cell arrangement
inside, differential-in, differntial-out, constant parallel Z-in of 5 KOhm
in parallel with a couple pFd each input. The gain control portion is
done by "starving" or actually redirecting the DC emitter current in the
input differential pair. Jameco (www.jameco.com) still sells this IC
at around $1.20 (?) in singles and has a copy of the Motorola data
for download on their website. That datasheet has a schematic of the
insides. That's good up into mid-VHF.

Some of the older JFETs had non-linear source-drain curves v. gate
voltage curves...see the difference in biasing for "depletion" and
"enhancement" mode operation. I don't know if they will work to
the top of HF range, though.



For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

The voltage gain of an effective regenerative stage is can be as high
as 100,000 as reported by Charles Kitchin. That's 100dB...not many op
amps have that kind of gain at say 10MHz.


I was suggesting using op-amp ICs WITH positive feedback. :-)

I'm just not going to buy "100 db voltage gain" in a regen based on
my own experiences...unless I see the bench layout and check the
calibration stickers on the test equipment determining this. :-)

Frankly, to get a simple receiver for HF, the Tayloe Mixer and its
separate LO followed by a low-noise AF range op-amp has the
most sensitivity for the fewest parts...and with little possibility of
re-radiating the oscillations of a regenerative due to a twitch of the
regeneration control. As a direct-conversion receiver, it can handle
CW or SSB and, with a stable LO, can take in conventional AM
with a lot less tweaking than a regen with a touchy regen control.

The most stable regen I ever built (three in all, the first using that
1T4) was with a 117N7 beam-power pentode and rectifier diode, AF
out driving an old, old high-impedance dynamic speaker. Plate curves
of that tube were of the sharp-cutoff variety. AM BC band, not much
else to listen to for entertainment in 1948. I suspect it was acting
more like a "plate detector" but it had the sensitivity of a common
"all-American-five" AM table top radio receiver.

Some of the minimal-tube-complement receiver designs of older times
used regenerative detectors at the IF for sensitivity improvement. I
know of one old Hallicrafters S-38 (?) reworked that way. That receiver
had essentially an "all-American-five" tube lineup and no power
transformer. Somewhat unsafe, but useable.

Nostalgia isn't what it used to be...

Len Anderson
retired (from regular hours) electronic engineer person

IIRC the original nation sw-3 used a remote cutoff tetrode as the
regen detector, with a remote cutoff tetrode as the rf stage.
Of course they were first referred to as "supercontrol" tubes.

Avery Fineman wrote:
In article ,
(Bruce Kizerian) writes:


A regen operates at the hairy transition of self-oscillation where
positive feedback yields a tremendous increase in gain. Doesn't
matter whether it is vacuum tube or transistor. The only difference
between remote-cutoff and sharp cutoff characteristics (transistors
of the bipolar junction type are very sharp cutoff equivalents to
tubes) would be on the amount of spurious garbage created when
the regen jumps into full oscillation.

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.


I know of no solid state equivalent (without some sort of AGC feedback
loop) for the remote cutoff pentode. Does anyone know if there is?

"AGC in a regen?"

Here, I was speaking in more general terms and not referring to
regenerative circuits.


If you are speaking in general terms then there are plenty of gain-
control elements out there. For a single-IC type of device, the
old Motorola MC1350 (8-pin DIP) is a sort-of Gilbert Cell arrangement
inside, differential-in, differntial-out, constant parallel Z-in of 5 KOhm
in parallel with a couple pFd each input. The gain control portion is
done by "starving" or actually redirecting the DC emitter current in the
input differential pair. Jameco (www.jameco.com) still sells this IC
at around $1.20 (?) in singles and has a copy of the Motorola data
for download on their website. That datasheet has a schematic of the
insides. That's good up into mid-VHF.

Some of the older JFETs had non-linear source-drain curves v. gate
voltage curves...see the difference in biasing for "depletion" and
"enhancement" mode operation. I don't know if they will work to
the top of HF range, though.



For experimentation purposes, a high gain-bandwidth product op-amp
IC might produce some interesting results. The gain-bandwidth (or
0 db open-loop gain frequency) of some op-amp ICs is up at 30 to
70 MHz now and the DC open-loop gain is enormous in comparison
to vacuum tubes. I sense possibilities of an op-am regen or even a
superregen on up through HF. Just a thought... :-)

The voltage gain of an effective regenerative stage is can be as high
as 100,000 as reported by Charles Kitchin. That's 100dB...not many op
amps have that kind of gain at say 10MHz.


I was suggesting using op-amp ICs WITH positive feedback. :-)

I'm just not going to buy "100 db voltage gain" in a regen based on
my own experiences...unless I see the bench layout and check the
calibration stickers on the test equipment determining this. :-)

Frankly, to get a simple receiver for HF, the Tayloe Mixer and its
separate LO followed by a low-noise AF range op-amp has the
most sensitivity for the fewest parts...and with little possibility of
re-radiating the oscillations of a regenerative due to a twitch of the
regeneration control. As a direct-conversion receiver, it can handle
CW or SSB and, with a stable LO, can take in conventional AM
with a lot less tweaking than a regen with a touchy regen control.

The most stable regen I ever built (three in all, the first using that
1T4) was with a 117N7 beam-power pentode and rectifier diode, AF
out driving an old, old high-impedance dynamic speaker. Plate curves
of that tube were of the sharp-cutoff variety. AM BC band, not much
else to listen to for entertainment in 1948. I suspect it was acting
more like a "plate detector" but it had the sensitivity of a common
"all-American-five" AM table top radio receiver.

Some of the minimal-tube-complement receiver designs of older times
used regenerative detectors at the IF for sensitivity improvement. I
know of one old Hallicrafters S-38 (?) reworked that way. That receiver
had essentially an "all-American-five" tube lineup and no power
transformer. Somewhat unsafe, but useable.

Nostalgia isn't what it used to be...

Len Anderson
retired (from regular hours) electronic engineer person

IIRC the original nation sw-3 used a remote cutoff tetrode as the
regen detector, with a remote cutoff tetrode as the rf stage.
Of course they were first referred to as "supercontrol" tubes.

I have used the 1Q5 with 18 volts and it worked well. It worked better with
27 volts.

Bill, N5NOB

I have used the 1Q5 with 18 volts and it worked well. It worked better with
27 volts.

Bill, N5NOB

Bruce Kizerian wrote:

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

My first regen RX was in 1947 with an A415 direct filament triode. (Does
anyone remember it?) It was followed by DC11 - a steel 1.5 V filament
tube - both excellent ones for regen receivers. (We used to call them
Audions.) Bruce says there are three types of regens : with tubes, with
FETs and with bipolar transistors. There is also a forth type: a
negative resistance reganeration receiver, an invention of mine (also
known as Lambda receiver). You can find its scematic in the British QRP
Club's magazine SPRAT: number 111, page 4 - with a correction in number
112, page 25, and a complete construction in SPRAT 113, page 17 - with a
correction in SPRAT 114, page 24. The schematic is a simulation of a
tunnel diode and works in the negative part of the U/I characteristic.
It does not have a feedback coil, and the regeneration is very soft - so
the worst problem has been solved. Its stability is not convenient for
CW or SSB, but it is excellent for broadcast stations from 500 kHz to 30
MHz; a real project for beginners. If someone duplicates it, I will be
happy to hear about his experience - by e-mail
. hr) or on this group. Best wishes,
Bozidar, 9A2HL

Bruce Kizerian wrote:

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

My first regen RX was in 1947 with an A415 direct filament triode. (Does
anyone remember it?) It was followed by DC11 - a steel 1.5 V filament
tube - both excellent ones for regen receivers. (We used to call them
Audions.) Bruce says there are three types of regens : with tubes, with
FETs and with bipolar transistors. There is also a forth type: a
negative resistance reganeration receiver, an invention of mine (also
known as Lambda receiver). You can find its scematic in the British QRP
Club's magazine SPRAT: number 111, page 4 - with a correction in number
112, page 25, and a complete construction in SPRAT 113, page 17 - with a
correction in SPRAT 114, page 24. The schematic is a simulation of a
tunnel diode and works in the negative part of the U/I characteristic.
It does not have a feedback coil, and the regeneration is very soft - so
the worst problem has been solved. Its stability is not convenient for
CW or SSB, but it is excellent for broadcast stations from 500 kHz to 30
MHz; a real project for beginners. If someone duplicates it, I will be
happy to hear about his experience - by e-mail
. hr) or on this group. Best wishes,
Bozidar, 9A2HL

Bruce Kizerian wrote:

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

I built my first regenerative receiver in 1947 with an A415
direct filament tube, followed by one with a steel DC11 - 1,5 V
direct filament tube - both excellent ones for the purpose. (Does
anyone remember them?). Bruce says there are three types of regen
receivers: the tube ones, the ones with a FET, and the ones with bipolar
transistors. However, there is also a fourth one: the negative
resistance reganerative receiver, known also as a Lambda receiver . The
oscillator is a transistor immitation of the tunnel diode, and the
negative resistance substitutes the feedback coil. It is my own
construction. You can find its schematic in the British QRP Club
magazine SPRAT No. 111, page 4 (with a correction in No. 112, page 25).
The whole construction with a PCB has been published in SPRAT No. 113,
page 17 (with a correction in SPRAT 114, page 24). The RX does not have
a feedback coil, and the regeneration is very smooth and rather even
over the whole band. So, that problem has been solved for good. It is
not stable enough for CW or SSB, but it is excellent for AM
broadcast stations from 500 kHz up to 30 MHz (with corresponding coils,
of course). So, according to my opinion, it is excellent for beginners
because they do not have to bother with the feedback coils.

If anyone would care to duplicate it, I would appreciate it
very much if I could hear about his experiences with it (on this group
or by e-mail: ). The whole project is still
open for experimentation. Best wishes,

Bozidar, 9A2HL

Bruce Kizerian wrote:

But it does matter. In the heirarchy of regen devices tubes provide
the "smoothest" regeneration, followed by FETs, with bipolar
transistors generally taking a distant third. I am not asking because
I have never built a regen. I have built DOZENS of them, and I sell a
simple version on my website...but I'm always looking for a new
approach.

I built my first regenerative receiver in 1947 with an A415
direct filament tube, followed by one with a steel DC11 - 1,5 V
direct filament tube - both excellent ones for the purpose. (Does
anyone remember them?). Bruce says there are three types of regen
receivers: the tube ones, the ones with a FET, and the ones with bipolar
transistors. However, there is also a fourth one: the negative
resistance reganerative receiver, known also as a Lambda receiver . The
oscillator is a transistor immitation of the tunnel diode, and the
negative resistance substitutes the feedback coil. It is my own
construction. You can find its schematic in the British QRP Club
magazine SPRAT No. 111, page 4 (with a correction in No. 112, page 25).
The whole construction with a PCB has been published in SPRAT No. 113,
page 17 (with a correction in SPRAT 114, page 24). The RX does not have
a feedback coil, and the regeneration is very smooth and rather even
over the whole band. So, that problem has been solved for good. It is
not stable enough for CW or SSB, but it is excellent for AM
broadcast stations from 500 kHz up to 30 MHz (with corresponding coils,
of course). So, according to my opinion, it is excellent for beginners
because they do not have to bother with the feedback coils.

If anyone would care to duplicate it, I would appreciate it
very much if I could hear about his experiences with it (on this group
or by e-mail: ). The whole project is still
open for experimentation. Best wishes,

Bozidar, 9A2HL

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

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

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

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!)