Self-excited Beam Deflection mixers?? Opinions???
 

Still mulling over some RX design changes for a HBR receiver project that I
am considering building. It is going to be an updated version of the HBR
receiver projects that W6TC, Ted Crosby, penned for QST in the late 50s and
early 60s.

I've decided to go with 6EH7 semi-remote pentodes for the RF and IF stages
(overload resistant), meaning my filament current requirements are going out
of sight.. 4.7 amps so far, so I want to cut back on the number of stages.

To cut my tube count and heater energy, I'm looking for opinions on using
6JH8s with self excited injection. The 2nd mixer requires 1515kc injection,
and I'm considering using the 6JH8 as a self-excited crystal oscillator to
eliminate using a separate oscillator stage. Original plan was either a 6BH6
oscillator, or 6U8 combined osc/buffer.

Second branstorm is to use a self-excited 6JH8 for the Product Detector and
85kc BFO, eliminating a separate tube and buffer stage that I had originally
planned on using (another 6U8). Will osc. pulling be a problem? Any other
drawbacks?

First mixer will be a 6ES8 Pullen, with a 6U8 used for the tunable LO and
buffer isolation. AGC will be via a 12AU7 plate detector, 12AU7 infinite
impedance AM detector, 12AX7 Q-multiplier, 12AU7 first AFA and S-meter amp,
and a 6AK6 AFA. First IF is 1600kc using cascaded modified ARC-5 IF
transformers. 2nd IF is 85kc, using cascaded R-23 command RX IFTs.

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

FWIW, I found some good material on this subject in the
March 1960 QST, pps 33 - 38.

Another question: I've been told that the 6JH8 works best
with 0 volts on the deflector electrodes. However, it was
common practice with the 7360 to use a voltage divider
between the plate and deflector to provide negative feedback
(improved linearity) while biasing and balancing the
deflection electrodes. I'm thinking of using the same scheme
on the 6JH8, except having the low end of the voltage
dividers going to a negative bias source. That would allow
setting the electrode voltages to 0 volts, or slightly negative
or positive--whatever works best--while still keeping the
advantages of having negative feedback from the plate.
Is this worth doing?

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:
Still mulling over some RX design changes for a HBR receiver project that I
am considering building. It is going to be an updated version of the HBR
receiver projects that W6TC, Ted Crosby, penned for QST in the late 50s and
early 60s.

I've decided to go with 6EH7 semi-remote pentodes for the RF and IF stages
(overload resistant), meaning my filament current requirements are going out
of sight.. 4.7 amps so far, so I want to cut back on the number of stages.

To cut my tube count and heater energy, I'm looking for opinions on using
6JH8s with self excited injection. The 2nd mixer requires 1515kc injection,
and I'm considering using the 6JH8 as a self-excited crystal oscillator to
eliminate using a separate oscillator stage. Original plan was either a 6BH6
oscillator, or 6U8 combined osc/buffer.

Second branstorm is to use a self-excited 6JH8 for the Product Detector and
85kc BFO, eliminating a separate tube and buffer stage that I had originally
planned on using (another 6U8). Will osc. pulling be a problem? Any other
drawbacks?

First mixer will be a 6ES8 Pullen, with a 6U8 used for the tunable LO and
buffer isolation. AGC will be via a 12AU7 plate detector, 12AU7 infinite
impedance AM detector, 12AX7 Q-multiplier, 12AU7 first AFA and S-meter amp,
and a 6AK6 AFA. First IF is 1600kc using cascaded modified ARC-5 IF
transformers. 2nd IF is 85kc, using cascaded R-23 command RX IFTs.

Pete


Early SSB exciters used the 7360 tube as a mixer / vfo so I know this
type of tube will work as a self excited converter. As far as pulling
is concerned this would depend on the difference between the oscillator
and IF frequencies, or the oscillator and signal frequencies. But
pulling shouldn't be any worse than with the pentode mixers that
couplied the oscillator to the same grid as the signal input. At least
the 7360 isolates the signal and oscillator to different electrodes.
Also the signal input is balanced and shielded by the screen grid.
OTHO I don't know how good (stable) an oscillator this tube is.
Probably better as a crystal oscillator than a vfo.

Self-excited Beam Deflection mixers?? Opinions???
 

ken scharf wrote:

Early SSB exciters used the 7360 tube as a mixer / vfo so I know this
type of tube will work as a self excited converter. As far as pulling
is concerned this would depend on the difference between the oscillator
and IF frequencies, or the oscillator and signal frequencies. But
pulling shouldn't be any worse than with the pentode mixers that
coupled the oscillator to the same grid as the signal input. At least
the 7360 isolates the signal and oscillator to different electrodes.
Also the signal input is balanced and shielded by the screen grid.
OTHO I don't know how good (stable) an oscillator this tube is.
Probably better as a crystal oscillator than a vfo.

The very /best/ mixer I ever made used the 7360.

I tried several other types of valve ("tube" - U.S.) mixer, but /nothing/
came even slightly close. The isolation of the local oscillator from the
incoming signal, the conversion gain, the accuracy of balance and the
bomb-proof nature of the mixer made it superior to /anything/ else I've
ever tried. In my receiver, there's a font-end amplifier, using a
variable-mu pentode then the 7360. It handles a bigger dynamic range
than /any/ other mixer.

The VFO is a "Kallitron" type, using two FETs and a PIC-based huff-and-puff
stabiliser (in 10 Hz steps) and two bipolar buffer amplifiers to drive the
grids of the 7360. The PIC also drives an LCD display of frequency, and
frequency stability is spectacular.

I can assure you - /there/ /is/ /no/ /substitute/ for the 7360. Simply
don't consider /anything/ else. Professionally, I've worked extensively
on "H-mode" switched mixers - often using very advanced components - and
can tell you that the 7360 out-performs /everything/ else!

Chris

Self-excited Beam Deflection mixers?? Opinions???
 

posted & mailed

Bob wrote:

ken scharf wrote:

Early SSB exciters used the 7360 tube as a mixer / vfo so I know this
type of tube will work as a self excited converter. As far as pulling
is concerned this would depend on the difference between the oscillator
and IF frequencies, or the oscillator and signal frequencies. But
pulling shouldn't be any worse than with the pentode mixers that
coupled the oscillator to the same grid as the signal input. At least
the 7360 isolates the signal and oscillator to different electrodes.
Also the signal input is balanced and shielded by the screen grid.
OTHO I don't know how good (stable) an oscillator this tube is.
Probably better as a crystal oscillator than a vfo.

The very /best/ mixer I ever made used the 7360.

I tried several other types of valve ("tube" - U.S.) mixer, but /nothing/
came even slightly close. The isolation of the local oscillator from the
incoming signal, the conversion gain, the accuracy of balance and the
bomb-proof nature of the mixer made it superior to /anything/ else I've
ever tried. In my receiver, there's a front-end amplifier, using a
variable-mu pentode then the 7360. It handles a bigger dynamic range
than /any/ other mixer.

The VFO is a "Kallitron" type, using two FETs and a PIC-based
huff-and-puff stabiliser (in 10 Hz steps) and two bipolar buffer
amplifiers to drive the
grids of the 7360. The PIC also drives an LCD display of frequency, and
frequency stability is spectacular.

I can assure you - /there/ /is/ /no/ /substitute/ for the 7360. Simply
don't consider /anything/ else. Professionally, I've worked extensively
on "H-mode" switched mixers - often using very advanced components - and
can tell you that the 7360 out-performs /everything/ else!

One other thing - self-excited mixers /never/ perform well. You should
re-think your approach.

Chris

Self-excited Beam Deflection mixers?? Opinions???
 

I'll reply to two posts at once!

Tio Pedro wrote:

Still mulling over some RX design changes for a HBR receiver project that I
am considering building. It is going to be an updated version of the HBR
receiver projects that W6TC, Ted Crosby, penned for QST in the late 50s and
early 60s.

Interesting! But be aware that the W6TC design has its flaws.

The first is that there are a lot of stages before you get to the
selectivity, which limits the dynamic range. The second is that the
tunable LO operates at a high frequency on the upper bands and uses
plug-in coils, which limits the thermal and mechanical stability as
well as having different calibration on each band.

I've decided to go with 6EH7 semi-remote pentodes for the RF and IF stages
(overload resistant), meaning my filament current requirements are going out
of sight.

6EH7 is a good tube. The receiver part of my rig (google my call) uses
one in the RF stage and one in the first IF, with a 7360 mixer.

Some must-read QST articles a

W1DX's article about "what's wrong with our present receivers",
January, 1957

The Squires-Sanders article about using the 7360 as a receiver front-
end mixer, September 1963

The "Miser's Dream" rx with 7360 mixer and other neat ideas, by W1DX,
May 1965

W1KLK's "Experimental Receiver for 75 meter DX", February 1972

An article about the 7360 product detector for the HBR, December 1960

A 6 meter SSB transmitter using the 6JH8 as a high-level balanced
modulator, October 1963

The RSGB Handbooks of the 1960s are the best for receiver ideas using
the 7360, IMHO.

I know of one design using the 6JH8 or its cousins the 6ME8 and 6HW8.
(The 6AR8 is an early tube that is reportedly microphonic).:

http://g4oep.atspace.com/retro/retro.htm

Worth a look!

4.7 amps so far, so I want to cut back on the number of stages.

One word: Don't. Use a bigger power transformer, or an auxiliary
heater transformer instead. The rx you describe is a big project, why
compromise it? With a separate heater transformer having its own power
switch, you could put the critical oscillator heaters on it and let
them run semi-continuously.

To cut my tube count and heater energy, I'm looking for opinions on
using
6JH8s with self excited injection. The 2nd mixer requires 1515kc injection,
and I'm considering using the 6JH8 as a self-excited crystal oscillator to
eliminate using a separate oscillator stage. Original plan was either a 6BH6
oscillator, or 6U8 combined osc/buffer.

The 6BH6 draws only 0.15 A of heater current. IMHO that small saving
is not worth the compromise.

Self-exciting the 6JH8 means the signal will go into the deflectors
rather than the grid. That's the opposite of usual receiver-mixer
practice, where the oscillator feeds the deflectors. I don't know what
the noise figure will be, but I do know that all the beam-deflection
receiver mixers I've seen put the signal into the grid for high gain
and low noise.

The only places I've seen the signal on the deflectors and the
oscillator on the grid is in high-signal-level applications like
transmitting balanced modulators and mixers, and receiving product
detectors, where noise figure isn't really an issue and low gain is
OK.

Second branstorm is to use a self-excited 6JH8 for the Product Detector and
85kc BFO, eliminating a separate tube and buffer stage that I had originally
planned on using (another 6U8). Will osc. pulling be a problem? Any other
drawbacks?

I don't know if you really need a buffer stage on the BFO. A 6BH6 will
do the job. See above about where the signal goes.

First mixer will be a 6ES8 Pullen, with a 6U8 used for the tunable LO and
buffer isolation.

How stable an oscillator is acceptable?

AGC will be via a 12AU7 plate detector, 12AU7 infinite
impedance AM detector, 12AX7 Q-multiplier, 12AU7 first AFA and S-meter amp,
and a 6AK6 AFA. First IF is 1600kc using cascaded modified ARC-5 IF
transformers. 2nd IF is 85kc, using cascaded R-23 command RX IFTs.
FWIW, I found some good material on this subject in the
March 1960 QST, pps 33 - 38.

Straight out of the RCA Transmitting Tube manual. (RCA considered the
7360 to be a transmitting tube!)

Another question: I've been told that the 6JH8 works best
with 0 volts on the deflector electrodes. However, it was
common practice with the 7360 to use a voltage divider
between the plate and deflector to provide negative feedback
(improved linearity) while biasing and balancing the
deflection electrodes.

I'm not sure about the negative-feedback part but I do know the idea
was balance. And the 7360 deflectors were supposed to be biased a
couple dozen volts positive.

I'm thinking of using the same scheme
on the 6JH8, except having the low end of the voltage
dividers going to a negative bias source. That would allow
setting the electrode voltages to 0 volts, or slightly negative
or positive--whatever works best--while still keeping the
advantages of having negative feedback from the plate.
Is this worth doing?

Only way to know for sure is to try. See the G4OEP rx page.

73 es GL de Jim, N2EY

Self-excited Beam Deflection mixers?? Opinions???
 

wrote in message
...

Tio Pedro wrote:
Interesting! But be aware that the W6TC design has its flaws.

The first is that there are a lot of stages before you get to the
selectivity, which limits the dynamic range.

I was seriously considering adding a half-lattice crystal filter at the
first IF; the IF filter in the Heath HR-10 would be do the job. Now,
to find a junker! I'll probably end up cascading
IF transformers at 1600kc to improve the shape factor and hopefully
improve the dynamic range numbers for signals further out on the
filter slopes. I have the transformers, so I might as well use them
in this lifetime.

The second is that the
tunable LO operates at a high frequency on the upper bands and uses
plug-in coils, which limits the thermal and mechanical stability as
well as having different calibration on each band.

But each LO coil is hand calibrated for thermal drift :) I'd think the
Q would be much better using full-sized plug-in coils vs. phenolic
bandswitches and a compromised inductors. Ted's design ran the
LO on low side injection and used second harmonic injection for
the first mixer on the upper bands. That really sucks and kills the
idea of balanced beam tube in the first mixer. I agree, the design
is dated, and the advent of cheap IF filters killed the design. The
harmonic mixing scheme really bothers me.

6EH7 is a good tube. The receiver part of my rig (google my call) uses
one in the RF stage and one in the first IF, with a 7360 mixer.

Been, there, done that :) Getting to see a lot of nice RXs searching
the web!

One word: Don't. Use a bigger power transformer, or an auxiliary
heater transformer instead. The rx you describe is a big project, why
compromise it? With a separate heater transformer having its own power
switch, you could put the critical oscillator heaters on it and let
them run semi-continuously.


As you noted, the design is inherently limited..

Self-exciting the 6JH8 means the signal will go into the deflectors
rather than the grid. That's the opposite of usual receiver-mixer
practice, where the oscillator feeds the deflectors. I don't know what
the noise figure will be, but I do know that all the beam-deflection
receiver mixers I've seen put the signal into the grid for high gain
and low noise.

Check SSB Exciter Circuits Using a New Beam Deflection Tube,
by K2FF in the March 1960 QST. It is one of the better presentations
that appeared in QST. He also shows a self-excited product detector
circuit as one example. I'd think the advantage in the PD with
G1 injection might be improved BFO blowby rejection,
which could otherwise affect the AGC system?


I don't know if you really need a buffer stage on the BFO. A 6BH6 will
do the job. See above about where the signal goes.

The buffer could be used for a CF or phase inverter, if I wanted to
use BFO injection on both deflectors. I know only one needs to be
driven in practice.

First mixer will be a 6ES8 Pullen, with a 6U8 used for the tunable LO and
buffer isolation.

How stable an oscillator is acceptable?

Buffer stage is recommended practice with the Pullen Mixer. It's easier
to use the pentode/triode, and ending not needing to use the stage, than
to add it later..

I'm not sure about the negative-feedback part but I do know the idea
was balance. And the 7360 deflectors were supposed to be biased a
couple dozen volts positive.

The negative feedback is mentioned in the QST article; it applies to
the product detector circuit where the deflector bias is taken directly from
the plates of the tube.

73 es GL de Jim, N2EY

Thanks for the comments..

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

Bob wrote:
ken scharf wrote:

Early SSB exciters used the 7360 tube as a mixer / vfo so I know this
type of tube will work as a self excited converter. As far as pulling
is concerned this would depend on the difference between the oscillator
and IF frequencies, or the oscillator and signal frequencies. But
pulling shouldn't be any worse than with the pentode mixers that
coupled the oscillator to the same grid as the signal input. At least
the 7360 isolates the signal and oscillator to different electrodes.
Also the signal input is balanced and shielded by the screen grid.
OTHO I don't know how good (stable) an oscillator this tube is.
Probably better as a crystal oscillator than a vfo.

The very /best/ mixer I ever made used the 7360.

I tried several other types of valve ("tube" - U.S.) mixer, but /nothing/
came even slightly close. The isolation of the local oscillator from the
incoming signal, the conversion gain, the accuracy of balance and the
bomb-proof nature of the mixer made it superior to /anything/ else I've
ever tried. In my receiver, there's a font-end amplifier, using a
variable-mu pentode then the 7360. It handles a bigger dynamic range
than /any/ other mixer.

The VFO is a "Kallitron" type, using two FETs and a PIC-based huff-and-puff
stabiliser (in 10 Hz steps) and two bipolar buffer amplifiers to drive the
grids of the 7360. The PIC also drives an LCD display of frequency, and
frequency stability is spectacular.

I can assure you - /there/ /is/ /no/ /substitute/ for the 7360. Simply
don't consider /anything/ else. Professionally, I've worked extensively
on "H-mode" switched mixers - often using very advanced components - and
can tell you that the 7360 out-performs /everything/ else!

Chris

Sounds like you're building a receiver with only one tube in it (a 7360)
and everything else solid state. Then again the 7360 probably makes a
very good product detector too.

Self-excited Beam Deflection mixers?? Opinions???
 

Bob wrote:
ken scharf wrote:

Early SSB exciters used the 7360 tube as a mixer / vfo so I know this
type of tube will work as a self excited converter. As far as pulling
is concerned this would depend on the difference between the oscillator
and IF frequencies, or the oscillator and signal frequencies. But
pulling shouldn't be any worse than with the pentode mixers that
coupled the oscillator to the same grid as the signal input. At least
the 7360 isolates the signal and oscillator to different electrodes.
Also the signal input is balanced and shielded by the screen grid.
OTHO I don't know how good (stable) an oscillator this tube is.
Probably better as a crystal oscillator than a vfo.

The very /best/ mixer I ever made used the 7360.

I tried several other types of valve ("tube" - U.S.) mixer, but /nothing/
came even slightly close. The isolation of the local oscillator from the
incoming signal, the conversion gain, the accuracy of balance and the
bomb-proof nature of the mixer made it superior to /anything/ else I've
ever tried. In my receiver, there's a font-end amplifier, using a
variable-mu pentode then the 7360. It handles a bigger dynamic range
than /any/ other mixer.

The VFO is a "Kallitron" type, using two FETs and a PIC-based huff-and-puff
stabiliser (in 10 Hz steps) and two bipolar buffer amplifiers to drive the
grids of the 7360. The PIC also drives an LCD display of frequency, and
frequency stability is spectacular.

I can assure you - /there/ /is/ /no/ /substitute/ for the 7360. Simply
don't consider /anything/ else. Professionally, I've worked extensively
on "H-mode" switched mixers - often using very advanced components - and
can tell you that the 7360 out-performs /everything/ else!

Chris

The very first ARRL HB I ever owned (1967) used the 7360 in the mixer
stage of a classic receiver (HB67) as well as another design (junior
misers dream). The first receiver was an 80 meter single conversion set
with a crystal controlled converter ahead of it. Similar commerical
designs were the HA350 and the 2B. The HB67 used a 6D10 compactron as
the first mixer/oscillator in the converter section. The MMD receiver
had the 7360 in the front end (NO RF stage) with a first IF of 3300 KHZ.
An RF Q multiplier was used instead of the RF stage. As you mentioned
the oscillator injected into the deflection plates in both cases

Self-excited Beam Deflection mixers?? Opinions???
 

ken scharf wrote:

Sounds like you're building a receiver with only one tube in it (a 7360)
and everything else solid state. Then again the 7360 probably makes a
very good product detector too.

No - the RF amplifier stage is a variable mu pentode, and there are more
variable mu valves used in the IF, another 7360 for the product detector,
and the rest is solid state. The hybrid approach seemed best - for
example, the variable current drawn by the audio stages is /entirely/
isolated from the IF supply, the front end supply and the local oscillator
supply. At the moment, it's a single conversion superhet, with a 10.7 MHz
IF (because I have 10.7 MHz filters), though I'm considering making it dual
conversion, with a very high first IF, to improve the inherent image
problems.

C.

Self-excited Beam Deflection mixers?? Opinions???
 

Bob wrote:
ken scharf wrote:

Sounds like you're building a receiver with only one tube in it (a 7360)
and everything else solid state. Then again the 7360 probably makes a
very good product detector too.

No - the RF amplifier stage is a variable mu pentode, and there are more
variable mu valves used in the IF, another 7360 for the product detector,
and the rest is solid state. The hybrid approach seemed best - for
example, the variable current drawn by the audio stages is /entirely/
isolated from the IF supply, the front end supply and the local oscillator
supply. At the moment, it's a single conversion superhet, with a 10.7 MHz
IF (because I have 10.7 MHz filters), though I'm considering making it dual
conversion, with a very high first IF, to improve the inherent image
problems.

C.

One project that I have been considering would be a re-creation of the
classic Drake 2B receiver. This receiver was a dual conversion 80 meter
receiver with an additional converter for other bands (making it a
triple conversion). The receiver covered 600khz of the 80 meter band
(3.5-4.1 mhz), the first IF was 455 khz, and the second IF was 50 khz.
I have several sets of IF cans from BC453 receivers (85khz) and a 2.7
khz Collins filter that could be used instead of an IF transformer for
the first IF.

I was thinking of using compactrons in the set, a single 6AR11 for the
85 khz IF, a 6D10 for the product detector and bfo, a 6AF11 for the AF
stage and S meter amp. A 6AG11 would serve as an AGC tube and AM
detector. The second (third?) mixer would be a 6BE6 (455-85), the
first and second mixers would be 7360's (expensive!). The first (xtal)
hfo would be solid state (maybe a pll), the second hfo (vfo) would also
be solid state. I have several nice three gang capacitors from ARC-5
receivers with dial gear drive that would work nicely. The completed
set would look more like the 2C because of the dial unless I ever find
another Edystone dial. (I had one in the junk box for a few years and
sold it on ebay to someone building an HBR. Got a kings ransom for it too).

Self-excited Beam Deflection mixers?? Opinions???
 

"ken scharf" wrote in message
. ..
Bob wrote:
I was thinking of using compactrons in the set, a single 6AR11 for the
85 khz IF, a 6D10 for the product detector and bfo, a 6AF11 for the AF
stage and S meter amp. A 6AG11 would serve as an AGC tube and AM
detector. The second (third?) mixer would be a 6BE6 (455-85), the first
and second mixers would be 7360's (expensive!). The first (xtal) hfo
would be solid state (maybe a pll), the second hfo (vfo) would also be
solid state. I have several nice three gang capacitors from ARC-5
receivers with dial gear drive that would work nicely. The completed set
would look more like the 2C because of the dial unless I ever find another
Edystone dial. (I had one in the junk box for a few years and sold it on
ebay to someone building an HBR. Got a kings ransom for it too).

The 6JH8 should work as well as the 7360 in a receiver mixer.
Swan changed to the 6JH8, probably for cost reasons.
( http://members.shaw.ca/pacifictv/cartridg.htm )

Not to make you feel bad, Ken... But, I still have an Eddystone
squirreled away for my HBR project. I think the Drake 2C
version makes more sense, though. The plug in coils and
oscillator LO scheme used by W6TC in the HBR
series leaves a bit to be desired.

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:
"ken scharf" wrote in message
. ..
Bob wrote:
I was thinking of using compactrons in the set, a single 6AR11 for the
85 khz IF, a 6D10 for the product detector and bfo, a 6AF11 for the AF
stage and S meter amp. A 6AG11 would serve as an AGC tube and AM
detector. The second (third?) mixer would be a 6BE6 (455-85), the first
and second mixers would be 7360's (expensive!). The first (xtal) hfo
would be solid state (maybe a pll), the second hfo (vfo) would also be
solid state. I have several nice three gang capacitors from ARC-5
receivers with dial gear drive that would work nicely. The completed set
would look more like the 2C because of the dial unless I ever find another
Edystone dial. (I had one in the junk box for a few years and sold it on
ebay to someone building an HBR. Got a kings ransom for it too).

The 6JH8 should work as well as the 7360 in a receiver mixer.
Swan changed to the 6JH8, probably for cost reasons.
( http://members.shaw.ca/pacifictv/cartridg.htm )

Not to make you feel bad, Ken... But, I still have an Eddystone
squirreled away for my HBR project. I think the Drake 2C
version makes more sense, though. The plug in coils and
oscillator LO scheme used by W6TC in the HBR
series leaves a bit to be desired.

Pete


Well the plug in coil stock used by W6TC are also unobtainium these days
too. It IS possible to by raw polystyrene tubing of the right size, and
glue onto bases from dead tubes, or tube base plugs (both of which are
available from time to time). The APC variable caps are getting rare
these days, but good quality ceramic trimmers would sub and these are
not TOO hard to find.

I have a bunch of turret tv tuners with the removable strips and also
gave thought to building a receiver similar to the HBR's but with toroid
core coils switched in the tuner strips. I don't know if the toroid
cores were available to W6TC and if he would have used them.

I also have a dial drive from an HRO receiver if I ever get the desire
to build something even more antedeluvian!

Self-excited Beam Deflection mixers?? Opinions???
 

"ken scharf" wrote in message
. ..
Tio Pedro wrote:
"ken scharf" wrote in Well the plug
in coil stock used by W6TC are also unobtainium these days
too. It IS possible to by raw polystyrene tubing of the right size, and
glue onto bases from dead tubes, or tube base plugs (both of which are
available from time to time). The APC variable caps are getting rare
these days, but good quality ceramic trimmers would sub and these are not
TOO hard to find.


The APC caps (silver plated brass are needed for the LO coils) are
still available. I've read that over one million a month were produced
during WWII. How true that is, I don't know, but it was on a webpage
dedicated to the history of Hammarlund. You have to shop around,
but I've picked up a few dozen for around two bucks each.

The National polystrene coils were becoming scarce by the time
the last HBR ran in QST. Bill (exray) uses Garolite XXX tubing
(phenolic) for his plug in coils; a bit pricy for my tastes. Ted's
coils had Qs of around 150 or so.

I'm going to try using fiberglass tubing--fortunately I have the
poor ham's Q-meter (Heath QM-1) to verify the effectiveness of that
material. A kind soul sent me a few dozen expired tubes to salvage
the bases from. There's always plastic pill bottles, they've been
tried and pass the Q-Meter test.

I have a bunch of turret tv tuners with the removable strips and also gave
thought to building a receiver similar to the HBR's but with toroid core
coils switched in the tuner strips. I don't know if the toroid cores were
available to W6TC and if he would have used them.

W6TC went through great pains to eliminate drift in the LO coils,
I don't know if toroids are the best choice for oscillator coils.

I'm sure you're familiar with the turret tuner in the RCA
TW-2000?

I also have a dial drive from an HRO receiver if I ever get the desire to
build something even more antedeluvian!

Now you're talking!!

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:
The National polystrene coils were becoming scarce by the time
the last HBR ran in QST. Bill (exray) uses Garolite XXX tubing
(phenolic) for his plug in coils; a bit pricy for my tastes. Ted's
coils had Qs of around 150 or so.


I remember Allied radio and Lafayette radio both carrying those
polystyrene coil forms as late as the early 70's (The last HBR article
was in '64 IIRC). Those coil forms were NOT made by National Radio, the
National coil forms were made of dark brown plastic (bakelite?) or
ceramic material. Millen also made some plug in coils that were made of
an orange colored bakelite like material. The '67 HB had a novice
transmitter (1625 final) that used those coil forms, Allied Radio part
numbers given.

I had a few of those coil forms at one time purchased to build a one
tube regenerative receiver from the 'boy electrician' book by Alfred
Morgan. Barry electronics had the 1H4G tubes for 50 cents back then.

Ocean State Electronics was carrying the polystyrene coil forms a few
years ago. They also had some 'cloned' forms that would fit the old
National Radio SW3 receiver (same weird 6 pin base).

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:

The 6JH8 should work as well as the 7360 in a receiver mixer.
Swan changed to the 6JH8, probably for cost reasons.
( http://members.shaw.ca/pacifictv/cartridg.htm )

I've tried both, and the 7360 wins by a long way - it probably proves
that "you get what you pay for"! The 7360 gave me useful conversion gain,
a spectacularly high intercept, and as low a noise figure as you could ever
wish for.

Bob

Self-excited Beam Deflection mixers?? Opinions???
 

On Sep 21, 2:30�pm, Bob wrote:
Tio Pedro wrote:
The 6JH8 should work as well as the 7360 in a receiver mixer.
Swan changed to the 6JH8, probably for cost reasons.
( �http://members.shaw.ca/pacifictv/cartridg.htm)

That's true, but the Swan transceivers weren't using the 7360 as a
receiving mixer. They were using it as the balanced modulator in the
transmitter section, which is a very different job, and the 6JH8 was a
low-cost alternative.

The 6JH8 could probably be used (with mods) in a lot of SSB
transmitter projects from the hollowstate era, rather than the 7360.

I've tried both, and the 7360 wins by a long way - it
probably proves
that "you get what you pay for"! �The 7360 gave me
useful conversion gain,
a spectacularly high intercept, and as low a noise figure
as you could ever
wish for.

What circuit and values did you use, Bob? Voltages, balanced vs.
unbalanced, output and input circuits, etc.?

73 de Jim, N2EY

Self-excited Beam Deflection mixers?? Opinions???
 

wrote:
On Sep 21, 2:30�pm, Bob wrote:
Tio Pedro wrote:
The 6JH8 should work as well as the 7360 in a receiver mixer.
Swan changed to the 6JH8, probably for cost reasons.
( �http://members.shaw.ca/pacifictv/cartridg.htm)

That's true, but the Swan transceivers weren't using the 7360 as a
receiving mixer. They were using it as the balanced modulator in the
transmitter section, which is a very different job, and the 6JH8 was a
low-cost alternative.

The 6JH8 could probably be used (with mods) in a lot of SSB
transmitter projects from the hollowstate era, rather than the 7360.

I've tried both, and the 7360 wins by a long way - it
probably proves
that "you get what you pay for"! �The 7360 gave me
useful conversion gain,
a spectacularly high intercept, and as low a noise figure
as you could ever
wish for.

What circuit and values did you use, Bob? Voltages, balanced vs.
unbalanced, output and input circuits, etc.?

73 de Jim, N2EY
Just looked on bay.
Wow, the 7360 is as expensive as 1L6's!

Self-excited Beam Deflection mixers?? Opinions???
 

Self-excited Beam Deflection mixers?? Opinions???
 

"Bob" wrote in message
...
wrote:
Over the years, I've tried /every/ possible mixer topology, including
the
modern H-mode switching types (which are astonishingly good), but the 7360
can't be beaten.

Bob

Hi Bob

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?

Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is /much/
cheaper!

Bob

Self-excited Beam Deflection mixers?? Opinions???
 

"Bob" wrote in message
...
Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?

Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is
/much/
cheaper!

Bob

Yeah, and I had a shot at a sleeve of them for 60 bucks several months
back :( Unfortunately, they aren't going to get any less expensive as
time passes.

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:
"Bob" wrote in message
...
Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?
Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is
/much/
cheaper!

Bob

Yeah, and I had a shot at a sleeve of them for 60 bucks several months
back :( Unfortunately, they aren't going to get any less expensive as
time passes.

Pete


There were a few other BD tubes as well.
The 6AR8 and 6ME8 are also listed in the RCA receiving tube
manuals along with the 6JH8. I don't know about current price
and supply on those.

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:
"Bob" wrote in message
...
Tio Pedro wrote:

A lot of folks have reported good results using the 6JH8 in place
of the 7360; with a few reporting better linearity. They appear
to be pretty much the same as far as performance. Have you tried
one?
Yes I have. The results were disappointing compared to the 7360. Perhaps
my values weren't optimised. Maybe I should try again - the 6JH8 is
/much/
cheaper!

Bob

Yeah, and I had a shot at a sleeve of them for 60 bucks several months
back :( Unfortunately, they aren't going to get any less expensive as
time passes.

Pete


Also check out this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

Self-excited Beam Deflection mixers?? Opinions???
 

"ken scharf" wrote in Also check out
this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

That poster also claims there is no rejection of either input signal
(grid or deflection plates) offered by the 7360.
Being a balanced modulator, the grid
signal can be cancelled by balancing the plate circuit.
It is used for DSB generation in SSB rigs!

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

ken scharf wrote:

Also check out this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

The writer's an idiot. The 7360 is good to over 50 MHz IF!

Bob

Self-excited Beam Deflection mixers?? Opinions???
 

Bob wrote:
ken scharf wrote:

Also check out this link, good info on the 7360 as a mixer.

Seems the 7360 performance is poor with IF's above 1mhz.

The writer's an idiot. The 7360 is good to over 50 MHz IF!

Bob
What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

Self-excited Beam Deflection mixers?? Opinions???
 

"ken scharf" wrote in message
. ..
The writer's an idiot. The 7360 is good to over 50 MHz IF!

Bob
What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

I have to wonder if the guy took a broadband, untuned
PD circuit and tried to use it as a broadband mixer?

If that's the case, then the interelectrode c
apacities would definitely limit BW in a high
impedance circuit, unless they were
"tuned" out using a LC resonant circuit. I ran into that
headscratcher trying to figure out how to drive the
deflectors using a broadband balun type arrangement;
like was done in the Squires RX.

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

ken scharf wrote:

What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

I get useful conversion gain at higher frequencies (though it's reduced) and
it's easily compensated for by the AGC. I found that I needed fairly
consistent IF signal levels for best performance of my crystal filters.

I appreciate the conversion /loss/ of diode ring mixers, but I find that
amplifying, then attenuating, then amplifying again tends to introduce
additional unwanted noise that can be avoided by use of a sensible gain
distribution. Diode mixers also don't handle very large signal levels very
well, and can produce some very strange results when over driven! I can't
really understand the love that some designers have for them.

My newer design approach is to use a switching ring of FETs, but the results
still can't match up to the 7360.

Bob

Self-excited Beam Deflection mixers?? Opinions???
 

Tio Pedro wrote:

I have to wonder if the guy took a broadband, untuned
PD circuit and tried to use it as a broadband mixer?

Almost certainly. He was therefore destined to fail completely!

If that's the case, then the interelectrode
capacities would definitely limit BW in a high
impedance circuit, unless they were
"tuned" out using a LC resonant circuit.

Exactly. "Tuning them out" would make the mixer somewhat less "broadband"!

I ran into that
headscratcher trying to figure out how to drive the
deflectors using a broadband balun type arrangement;
like was done in the Squires RX.

I looked at the Squires design, and it was very clever, but seemed to
require some obscure components that were unobtainable.

Bob

Self-excited Beam Deflection mixers?? Opinions???
 

Bob wrote:

My newer design approach is to use a switching ring of FETs, but the results
still can't match up to the 7360.
Do you use the fets as passive switches, or do you apply power between
the source/drain? What kind of fets (IE: depletion mode jfets or
enhancement mode mosfets)?

Can you post the 7360 mixer circuit you use somewhere?

BTW these tubes (7360, 6AR8, 6JH8, 6ME8) are sensitive to magnetic
fields and need to be shielded for best results. James Millen used to
make a mu-metal shield that would fit over tubes this size. I would
suspect unshielded tubes could be the reason for the poor results
obtained with some of the color tv versions of these tubes.

Also the 7360 is shown as a tetrode, while the color tv tubes are
pentodes (ie: they have three grids), but grid #2 is grounded and grid
#3 has normal 'screen' voltage applied. Grid #2 is internally connected
to the heater or cathode for these tubes.

Self-excited Beam Deflection mixers?? Opinions???
 

"ken scharf" wrote in message
news:RoADk.41384
ken scharf wrote:

What he claimed was that the conversion gain dropped to unity above
that frequency. That doesn't mean it isn't a good mixer at 50mhz.
Diode ring mixers have a unity (or LESS!) conversion gain, yet they
are very good mixers.

The conversion gain should be much greater than unity
for any of those balanced mixers. He was doing
something wrong to write statements like those.

Regarding the DBMs, sure they have some loss,
but the losses basically sets the mixer noise figure.
Add a few dB loss for the the front-end preselector
filtering, and may 8 dB loss for the mixer, followed
by a strong, low noise IF amplifier, and your pretty
much good to go, on the HF bands anyway..

DBMs like to be driven by symmetrical
LO waveforms (square wave is great) and the port
terminations are critical as well. My own experience
with them is that the supporting stages also need good
shielding, filtering and bypassing, they are great
harmonic mixers from DC to light!

I'm sure Bob's H-Ring designs are suberb; I've
pretty stopped playing with mixer circuits after the
DBMs became available well over 20 years ago!

Pete

Self-excited Beam Deflection mixers?? Opinions???
 

ken scharf wrote:

Can you post the 7360 mixer circuit you use somewhere?

I'll send you an email tomorrow. I'll have to scan my sketches - as with
all the best projects, the documentation was "informal"! ;)

Bob