As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** Prior art pointers, anyone? ******

TIA

Filippo N1JPR






___________________________________________

P.S.: Just to prempt repetitions of the obvious I'll repeat it myself:
Why don't you use a [ superhet ¦ xtal roofing filter ¦ downconversion
¦ cod liver oil ¦ snake oil ]. Sorry I never heard of it, so it's
likely to be a bad idea. Are you a Communist? Never heard of a 40MHz
cavity. A superregen won't demod [ CW ¦ SSB ¦ [QM¦P]SKxx ¦ delta-
sigma ¦ ancient Greek ] ! Is this gonna be a portable receiver in
that you can put it in the back of a SUV - if someone helps you carry
the 6' long cavity, that is? You will need a [ BFO ¦ product detector
¦ AMS ¦ DSP ¦ LPF ¦ postprocessing ¦ Photoshop ]. IF passband will be
too broad, although I have no idea how broad since I never used a
cavity for that. :-o

spamhog wrote:
As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** Prior art pointers, anyone? ******

"Coaxial Line V.H.F. Receivers", Joseph Santangelo, W1NXY, QST, March
1948, volume XXXII, number 3.

Basically it was a superregen using a coaxial cavity to increase the Q.
Reported sizes were 7.5" x 2" for the outer conductor, 7.5" by 0.5"
for the inner. The author's version was silver plated, but he reported
that aluminum and copper had been used. He loaded it with a cap to get
the right frequency.

It didn't look too hard to build, but its going to have to grow for 6m.
You _ought_ to be able to do this with CATV hardline if you don't mind
lots of connectors at the bends or a really long, skinny radio. You
_may_ be able to get a decent Q just using some really efficient
flexible coax, coiled up. I'd even see if I could find some
semi-hardline that I could bend into a serpentine shape, were I playing
with this notion.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Apr 14, 2:55*pm, Tim Wescott wrote:
spamhog wrote:
As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. *The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** * Prior art pointers, anyone? * *******

"Coaxial Line V.H.F. Receivers", Joseph Santangelo, W1NXY, QST, March
1948, volume XXXII, number 3.

Basically it was a superregen using a coaxial cavity to increase the Q.
* Reported sizes were 7.5" x 2" for the outer conductor, 7.5" by 0.5"
for the inner. *The author's version was silver plated, but he reported
that aluminum and copper had been used. *He loaded it with a cap to get
the right frequency.

It didn't look too hard to build, but its going to have to grow for 6m.
You _ought_ to be able to do this with CATV hardline if you don't mind
lots of connectors at the bends or a really long, skinny radio. *You
_may_ be able to get a decent Q just using some really efficient
flexible coax, coiled up. *I'd even see if I could find some
semi-hardline that I could bend into a serpentine shape, were I playing
with this notion.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details athttp://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -

- Show quoted text -

I know a guy that built a stripline output circuit for a 6M amp.I
think it was about 4 ft long.

Jimmie

On Apr 14, 9:46*am, spamhog wrote:
As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. *The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** * Prior art pointers, anyone? * *******

TIA

Filippo N1JPR

___________________________________________

P.S.: Just to prempt repetitions of the obvious I'll repeat it myself:
Why don't you use a [ superhet ¦ xtal roofing filter ¦ downconversion
¦ cod liver oil ¦ snake oil ]. *Sorry I never heard of it, so it's
likely to be a bad idea. *Are you a Communist? *Never heard of a 40MHz
cavity. *A superregen won't demod [ CW ¦ SSB ¦ [QM¦P]SKxx ¦ delta-
sigma ¦ ancient Greek ] ! *Is this gonna be a portable receiver in
that you can put it in the back of a SUV - if someone helps you carry
the 6' long cavity, that is? *You will need a [ BFO ¦ product detector
¦ AMS ¦ DSP ¦ LPF ¦ postprocessing ¦ Photoshop ]. *IF passband will be
too broad, although I have no idea how broad since I never used a
cavity for that. *:-o

I think it's the APN141 that uses a gated regen with a cavity. You
might get some interesting ideas from it, if you can find any
documentation on it. It's a cute design that made me think "out of
the box" when I learned it many years ago.

You're talking about a low enough frequency that you'll probably
benefit from a calculation of the size of resonator you'll need to get
the same Q as you can get from an LC tank. I suspect that unless you
are willing to make a really big coaxial resonator, you'll be able to
do better with an LC tank, or equivalently a helical resonator. At
1GHz and above, a cavity or coaxial resonator usually makes a lot of
sense. At 1MHz, a cavity or coaxial resonator probably never makes
sense. At 50MHz---well, do some careful thinking about it before you
jump in. A coil a couple inches in diameter and two to four inches
long should get you to Qu well in excess of 1000, if you are careful
with the construction.

Cheers,
Tom

On Apr 14, 11:46�am, spamhog wrote:
As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. �The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** � Prior art pointers, anyone? � �******

TIA

Filippo N1JPR


IIRC N1TEV's design used a sine wave waveform in the quench
oscillator. As such the receiver is slope controlled, in which case
the bandwidth depends upon the rate of change of the admittance across
the tuned circuit as it goes into an oscillation condition, and not
the Q of the resonant circuit.

The standard reference is "Super-Regenerative Receivers", by J.R.
Whitehead, Cambridge University Press, 1950.

73 John KC0G

On Apr 15, 8:08�am, "
wrote:
On Apr 14, 11:46 am, spamhog wrote:

As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** Prior art pointers, anyone? ******

TIA

Filippo N1JPR

IIRC N1TEV's design used a sine wave waveform in the quench
oscillator. �As such the receiver is slope controlled, in which case
the bandwidth depends upon the rate of change of the admittance across
the tuned circuit as it goes into an oscillation condition, and not
the Q of the resonant circuit.

The standard reference is "Super-Regenerative Receivers", by J.R.
Whitehead, Cambridge University Press, 1950.

73 John �KC0G-

I meant to say "conductance" not "admittance"

Tim, Tom, Jimmie, John, thanks you all! This thing might work, There's
no way around the need to get my feet wet and build/find some cavity.

Filippo N1JPR

On Apr 15, 9:08*am, "
wrote:
On Apr 14, 11:46 am, spamhog wrote:





As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** Prior art pointers, anyone? ******

TIA

Filippo N1JPR

IIRC N1TEV's design used a sine wave waveform in the quench
oscillator. *As such the receiver is slope controlled, in which case
the bandwidth depends upon the rate of change of the admittance across
the tuned circuit as it goes into an oscillation condition, and not
the Q of the resonant circuit.

The standard reference is "Super-Regenerative Receivers", by J.R.
Whitehead, Cambridge University Press, 1950.

73 John *KC0G- Hide quoted text -

- Show quoted text -

Initially I thought the OP was going to incorporate the very high Q
resonant circuit in his converter , to me that would be the logical
thing to do, then I re-read it. Of course you are correct. I can
greatly appreciate that the OP wants to do things his way just
because thats the way he wants to do it. Given the complexity of the
circuit he is going to eventually have I think he should just build a
little superhet for his purposes.

Jimmie

On Apr 16, 8:42*am, spamhog wrote:
Tim, Tom, Jimmie, John, thanks you all! This thing might work, There's
no way around the need to get my feet wet and build/find some cavity.

Filippo N1JPR

Further to my comment about how big a coaxial resonator must be to get
high Q: to get Qu of 1000 at 50MHz will require an air-dielectric
line almost 1.5 inches OD. A quarter wavelength is about 60 inches;
you can shorten that some by loading the open end with capacitance,
but expect it will be at least half that long. Compare that with a
coil of 8 turns of #10 AWG copper wire 1.25 inches ID, spaced 2 wire
diameters center-to-center (less than 2 inches total length) that will
also give you a Qu over 1000.

I think if I had an overwhelming urge to try a design using a cavity
(or coaxial cavity) resonator, I'd do it at about 1GHz, or maybe even
500MHz, where I can make a resonator with high Qu in a practical size,
and where I can't wind a coil that's big enough to get really high Q
and also have a high self resonant frequency. For example, at 1GHz, a
quarter wave air dielectric cavity will be about 3 inches long, and if
I make it from "3/4-inch" copper pipe (properly cleaned), I can get Qu
well over 2000; it will be very tough to make a coil that has a self-
resonance above 1GHz that has a Qu even close to 1000 (short of using
superconducting wire!).

There are very practical reasons that you don't see cavity resonators
at low frequencies: you can do better with smaller, cheaper parts.

Cheers,
Tom