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.

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

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

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.

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.

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).

"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

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!

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

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