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  #41   Report Post  
Robert Casey
 
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I admire your improvements but it seems that since most all toob sets
are collecibles, changing the circuitry in any way would cause them to
be no longer "stock from the factory", i.e. they'd be modified. And if
you did modify a collectible radio without telling the buyer, it would
be grounds for calling you a dishonest seller.

True to some extent, though it would be an easily reversed mod. The
real reason
manufacturers didn't install this circuit was that it would cost one
resistor and one
capacitor extra, plus the labor of wiring it in. In a consumer product,
every
fraction of a penny you can shave becomes significant after millions of
units
made. And most people didn't seem to mind the extra distortion.

And as you said, there's
probably not much point in it for most cheaper
radios.'''''''''''''''''''''''''''''''''''''''''' '''''



I have to agree with the sentiments here about collectables,
but one reason I don't bother collecting many AM radios is their
poor sound, and to improve them, you have to modify them,
and I do just that if there is no other way to repair them,
and if an owner is happy about it.
Hopefully they'll run well for another 50 years, and the next repairist
will have to make similar decisions I have.



This same technique should help the AM section of a tuner sound better,
in those
receivers where AM was an afterthought ("Oh, just throw in a 6BE6, make
that
6BA6 FM IF amp also do the AM IF, and use the diodes of that 6AV6 over
there...").

  #42   Report Post  
Patrick Turner
 
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John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

In article ,
wrote:

Frank Dresser wrote:
I think the fact that the synchrodyne never became at all popular
as an AM
radio detector in the tube era means something. If I recall
correctly, I
read that synchrodyne detectors would howl until they sync'd.

Also, the
phasing would have to be perfect to get good demodulation from
normal double
sideband AM.

Now appearing on alt.binaries.pictures.radio

Syncrhodyne three tube receiver from the April 1951 edition of
Radio News.

Looks more like the article came from Radio Electronics than from Radio
News, no way of confirming the April 1951 date.

The synchrodyne schematic never appeared on ABPR
when I looked out for it.

Too bad, it's an Australian design from "down under".


Not all the postings of binaries are able to fit the pouches of the trained
kangaroo couriers who take binaries south,
from the north, to where they originated.
So the ABPR news group I see from my povety stricken ISP
often lacks the illuminations of the american views.


But this article gives the Australian view, being written by one John W.
Straede, who was a "Lecturer in electronics and electro-acoustics,
Melbourne Technical College, Australia."


There have been some bright Oz stars in the world of electronics over the years.

I have since recieved a copy of the synchrodyne from someone privately.
It basically uses two tubes to make the tuner, followed by a 6V6 audio output
and a there was a rectifier tube and has similarities to other
synchrodynes of the era, although it has a variable FB control
to the snyc tube oscilator-detector.
Its similar to another circuit I have.
I will have to scan and post a few for ppl soon.
These synchrodynes were slightly simpler circuits than a superhet
for the same number of tubes.

Patrick Turner.



Regards,

John Byrns

Surf my web pages at,
http://users.rcn.com/jbyrns/

  #43   Report Post  
John Byrns
 
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In article , Robert Casey
wrote:

Looks like an envelope detector can perform well. See my post
over in a.b.p.radio with diagrams. Below is the text without
the diagrams:

After reading Brian's web page on modulation acceptance
http://n2.net/k6sti/ma.htm
I decided to try some simulations of the AA5 envelope detector and
got results similar to Brian's page before any mods.
Then I decided to try using that second diode 12AV6's and 12SQ7s
come with. That second diode will do the AVC function, thus
leaving the first diode doing only the audio envelope detection. As
Brian described, the AVC filter cap tends to back bias the envelope
detector in convential AA5 circuits, causing clipping at low valleys of
the modulation. Moving the AVC to its own diode gets rid of that
problem. Also reducing the envelope detector resistance value to 150K
from 500K also helps (you will lose about 3dB of audio, which isn't that
much). And with the AVC now separate this will only mildly affect the
AVC (by about 1dB). And when you move the AVC pick-off cap to
the plate of the IF tube, this drop goes away. This was observed in a real
radio I tried this mod in.



There are a couple of other interesting effects that taking the AGC
voltage from the primary of the last IFT has. At first as we tune toward
the center of the pass band the voltage across the primary of the IFT
increases as expected, but then as we get close to the center the voltage
starts dropping, reaching a minimum when the carrier is centered in the
pass band. The AGC voltage follows and the effect is to sharpen the
apparent aural tuning characteristic because the decrease in AGC voltage
when center tuned increases the gain at that point.

If a tuning eye is fitted to this type of radio it is almost universally
connected to the audio detector rather than the AGC detector, which is
unfortunate from the AC loading point of view as the filter for the eye
tube often presents an even worse AC load than the AGC circuit. For the
longest time I couldn't figure out why the designers of most of these
radios made this apparently dumb mistake in connecting the eye tube, but I
eventually realized that if the eye tube was connected to the AGC line it
would have an unnatural and non intuitive visual tuning characteristic,
the dip at center tune might confuse the average consumer, although a
radio nut would probably delight in the effect as an indicator of exact
tuning.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/
  #44   Report Post  
Robert Casey
 
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If a tuning eye is fitted to this type of radio it is almost universally
connected to the audio detector rather than the AGC detector, which is
unfortunate from the AC loading point of view as the filter for the eye
tube often presents an even worse AC load than the AGC circuit.

Is that because of a resistor-capacitor filter between the audio
detector and the grid of
the eye tube? I would just feed the audio directly to the eye tube
grid, and place a
cap on the eye tube triode plate to do the filtering there.





  #45   Report Post  
Patrick Turner
 
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John Byrns wrote:

In article , Robert Casey
wrote:

Looks like an envelope detector can perform well. See my post
over in a.b.p.radio with diagrams. Below is the text without
the diagrams:

After reading Brian's web page on modulation acceptance
http://n2.net/k6sti/ma.htm
I decided to try some simulations of the AA5 envelope detector and
got results similar to Brian's page before any mods.
Then I decided to try using that second diode 12AV6's and 12SQ7s
come with. That second diode will do the AVC function, thus
leaving the first diode doing only the audio envelope detection. As
Brian described, the AVC filter cap tends to back bias the envelope
detector in convential AA5 circuits, causing clipping at low valleys of
the modulation. Moving the AVC to its own diode gets rid of that
problem. Also reducing the envelope detector resistance value to 150K
from 500K also helps (you will lose about 3dB of audio, which isn't that
much). And with the AVC now separate this will only mildly affect the
AVC (by about 1dB). And when you move the AVC pick-off cap to
the plate of the IF tube, this drop goes away. This was observed in a real
radio I tried this mod in.


There are a couple of other interesting effects that taking the AGC
voltage from the primary of the last IFT has. At first as we tune toward
the center of the pass band the voltage across the primary of the IFT
increases as expected, but then as we get close to the center the voltage
starts dropping, reaching a minimum when the carrier is centered in the
pass band. The AGC voltage follows and the effect is to sharpen the
apparent aural tuning characteristic because the decrease in AGC voltage
when center tuned increases the gain at that point.

If a tuning eye is fitted to this type of radio it is almost universally
connected to the audio detector rather than the AGC detector, which is
unfortunate from the AC loading point of view as the filter for the eye
tube often presents an even worse AC load than the AGC circuit. For the
longest time I couldn't figure out why the designers of most of these
radios made this apparently dumb mistake in connecting the eye tube, but I
eventually realized that if the eye tube was connected to the AGC line it
would have an unnatural and non intuitive visual tuning characteristic,
the dip at center tune might confuse the average consumer, although a
radio nut would probably delight in the effect as an indicator of exact
tuning.


But there is rarely a dip in the tuning character of most AM sets.

But I often derive the AGC voltage separately from
a small cap&diode off the anode of the last IF amp, where more AGC voltage is
available because the envelope amplitude is greater than at the secondary of the
IFT.

The IFTs can be aligned with a VTM attatched to the AGC voltage,
and the tuning done to generate the highest AGC.
There is usually only one peak, and if two tuning peaks are seen,
its often because of mis-alignment of the IF, or
the circuit has been configured for wide BW and has slightly over critically
coupled IFTs,
which rarely occurs in any ordinary domestic AM set.
Some sets with variable IF selectivity had a switched tertiary on IFT1,
so first you tuned with the eye for max peak, then switched the tertiary in for
wide band audio,
or for locals.

Patrick Turner.





Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/




  #46   Report Post  
Patrick Turner
 
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Robert Casey wrote:



If a tuning eye is fitted to this type of radio it is almost universally
connected to the audio detector rather than the AGC detector, which is
unfortunate from the AC loading point of view as the filter for the eye
tube often presents an even worse AC load than the AGC circuit.

Is that because of a resistor-capacitor filter between the audio
detector and the grid of
the eye tube? I would just feed the audio directly to the eye tube
grid, and place a
cap on the eye tube triode plate to do the filtering there.


The loading effects are removed when a CF buffer is connected to the last IFT
sec,
and the diode detection and eye drive voltage is derived from the low
impedance cathode
of the CF.

Patrick Turner.







  #47   Report Post  
t.hoehler
 
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I have to agree with the sentiments here about collectables,
but one reason I don't bother collecting many AM radios is their
poor sound, and to improve them, you have to modify them,
and I do just that if there is no other way to repair them,
and if an owner is happy about it.
Hopefully they'll run well for another 50 years, and the next repairist
will have to make similar decisions I have.


Which leads me to the question, will there be any AM stations to listen to
in fifty years? And, after reading and looking over Randy's excellent story
about the 5 KW AM transmitter, I wonder, will all postings like his just be
a memory in fifty years? If so, the future generation will be missing out on
a great deal of old, but really cool technology.

Regards to all,
Tom


  #48   Report Post  
Jon Noring
 
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t.hoehler wrote:
someone else wrote (attributes lost):


I have to agree with the sentiments here about collectables, but
one reason I don't bother collecting many AM radios is their poor
sound, and to improve them, you have to modify them, and I do just
that if there is no other way to repair them, and if an owner is
happy about it. Hopefully they'll run well for another 50 years,
and the next repairist will have to make similar decisions I have.


Which leads me to the question, will there be any AM stations to
listen to in fifty years? And, after reading and looking over
Randy's excellent story about the 5 KW AM transmitter, I wonder,
will all postings like his just be a memory in fifty years? If so,
the future generation will be missing out on a great deal of old,
but really cool technology.


Good question. It's hard to say where the MW BCB band will be in 50
years. Will there still be commercial stations? Will they broadcast
in digital rather than AM?

My son is very interested in getting the SSTRAN AM transmitter and
transmit music and alternative programming he is now broadcasting on
the Internet. He'd simply have an audio out of his server's sound
card to go to the transmitter. Maybe in 50 years the band will be
covered by more low-power broadcasting like what my son is interested
in? (he's intrigued with setting up transmitters every mile in the
neighborhood.) Who knows...

Jon

  #49   Report Post  
John Byrns
 
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In article , Robert Casey
wrote:

If a tuning eye is fitted to this type of radio it is almost universally
connected to the audio detector rather than the AGC detector, which is
unfortunate from the AC loading point of view as the filter for the eye
tube often presents an even worse AC load than the AGC circuit.

Is that because of a resistor-capacitor filter between the audio
detector and the grid of
the eye tube?


Yes

I would just feed the audio directly to the eye tube
grid, and place a
cap on the eye tube triode plate to do the filtering there.


If you feed the audio directly to the eye tube grid, and place a cap on
the eye tube triode plate you would probably get serious flickering of the
eye angle with modulation, as the charge and discharge time constants
would be quite different resulting rectification of the audio.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/
  #50   Report Post  
John Byrns
 
Posts: n/a
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In article , Patrick Turner
wrote:

John Byrns wrote:

There are a couple of other interesting effects that taking the AGC
voltage from the primary of the last IFT has. At first as we tune toward
the center of the pass band the voltage across the primary of the IFT
increases as expected, but then as we get close to the center the voltage
starts dropping, reaching a minimum when the carrier is centered in the
pass band. The AGC voltage follows and the effect is to sharpen the
apparent aural tuning characteristic because the decrease in AGC voltage
when center tuned increases the gain at that point.

If a tuning eye is fitted to this type of radio it is almost universally
connected to the audio detector rather than the AGC detector, which is
unfortunate from the AC loading point of view as the filter for the eye
tube often presents an even worse AC load than the AGC circuit. For the
longest time I couldn't figure out why the designers of most of these
radios made this apparently dumb mistake in connecting the eye tube, but I
eventually realized that if the eye tube was connected to the AGC line it
would have an unnatural and non intuitive visual tuning characteristic,
the dip at center tune might confuse the average consumer, although a
radio nut would probably delight in the effect as an indicator of exact
tuning.


But there is rarely a dip in the tuning character of most AM sets.


That was my point and is the reason sets with a tuning eye virtually
always connect the tuning eye to the audio detector, not to the AGC
rectifier.

But I often derive the AGC voltage separately from
a small cap&diode off the anode of the last IF amp, where more AGC voltage is
available because the envelope amplitude is greater than at the

secondary of the
IFT.

The IFTs can be aligned with a VTM attatched to the AGC voltage,
and the tuning done to generate the highest AGC.


Good luck with this approach, it is likely to result in misalignment, this
sort of set should be aligned either with a modulated oscillator and audio
VTVM on the output, or by measuring the detector voltage.

An interesting experiment on a set that takes the AGC from the IFT primary
is to short the secondary of the IFT with a clip lead, you will observe an
increase in AGC voltage when the secondary is shorted, this is the same
effect that causes the dip in primary voltage when properly tuned.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/


  #51   Report Post  
Patrick Turner
 
Posts: n/a
Default



"t.hoehler" wrote:

I have to agree with the sentiments here about collectables,
but one reason I don't bother collecting many AM radios is their
poor sound, and to improve them, you have to modify them,
and I do just that if there is no other way to repair them,
and if an owner is happy about it.
Hopefully they'll run well for another 50 years, and the next repairist
will have to make similar decisions I have.


Which leads me to the question, will there be any AM stations to listen to
in fifty years?


Yes, unless the Got of Triodes changes the laws of physics,
and dissallows RF propagation at the BCB.


And, after reading and looking over Randy's excellent story
about the 5 KW AM transmitter, I wonder, will all postings like his just be
a memory in fifty years?


In 50 years going back to recent postings about AM radios will be difficult.

If so, the future generation will be missing out on
a great deal of old, but really cool technology.


Someone somewhere will be working from first principles, and designing and
building
AM radios without any assistance from our postings, or RDH4.

What they miss out on is their worry, not mine.
The 4 year old now will have potentially a lot to look forward to,
cures for cancer, maybe a longer lifespan, slimming pills that
work without side effects to allow huge supersize macs to be
eaten without getting fat, or guilty about it, cars that use hydrogen,
perhaps cheaper energy, and lower winter heating bills.
He'll still have to deal with BS and face death and taxes.

But in 10,054, thing will be *very* different, and we humans might have
genetically
engineered themselves into a vastly different form indeed, and complete with
AM radio implants at birth from a test tube, or a cloning dish,
and the ability to eat rubbish from the vast landfill deposits which will have
nearly covered the planet entirely.
But infinite development is impossible with finite resources.
Methinks it might be just dusty in 100,054.
So if we will be gone by then, why are we here now?

Cool might be rare word to describe the world in 2054,
when temperatures will have climbed alarmingly,
and mainly because desperate western nation people have bought
even larger air-conditioning units.

The future may occur and be able to be considered, if we don't
poison ourselves and all the other species first. The current rate of species
extinctions
is much faster than at any other time in the history of life on
our bloomin dear little blue planet.
Is life making the same mistakes as us on the millions of other
bloomin little blue planets in the universe?
Do they listen to rock and roll and talkback shows to cool the soul too?

Patrick Turner.



Regards to all,
Tom


  #52   Report Post  
Patrick Turner
 
Posts: n/a
Default



John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

There are a couple of other interesting effects that taking the AGC
voltage from the primary of the last IFT has. At first as we tune toward
the center of the pass band the voltage across the primary of the IFT
increases as expected, but then as we get close to the center the voltage
starts dropping, reaching a minimum when the carrier is centered in the
pass band. The AGC voltage follows and the effect is to sharpen the
apparent aural tuning characteristic because the decrease in AGC voltage
when center tuned increases the gain at that point.

If a tuning eye is fitted to this type of radio it is almost universally
connected to the audio detector rather than the AGC detector, which is
unfortunate from the AC loading point of view as the filter for the eye
tube often presents an even worse AC load than the AGC circuit. For the
longest time I couldn't figure out why the designers of most of these
radios made this apparently dumb mistake in connecting the eye tube, but I
eventually realized that if the eye tube was connected to the AGC line it
would have an unnatural and non intuitive visual tuning characteristic,
the dip at center tune might confuse the average consumer, although a
radio nut would probably delight in the effect as an indicator of exact
tuning.


But there is rarely a dip in the tuning character of most AM sets.


That was my point and is the reason sets with a tuning eye virtually
always connect the tuning eye to the audio detector, not to the AGC
rectifier.


It may not be critical where you connect the feed to the magic eye in many old
radios.



But I often derive the AGC voltage separately from
a small cap&diode off the anode of the last IF amp, where more AGC voltage is
available because the envelope amplitude is greater than at the

secondary of the
IFT.

The IFTs can be aligned with a VTM attatched to the AGC voltage,
and the tuning done to generate the highest AGC.


Good luck with this approach, it is likely to result in misalignment, this
sort of set should be aligned either with a modulated oscillator and audio
VTVM on the output, or by measuring the detector voltage.


It works, and its not neccesary to use a modulated carrier.
A carrier of exactly the 455 kHz can even be cap coupled via 10 pF applied to the
antenna terminal
with the set tuned as low as it will go, and the IF tuned up starting on the last
IF and
moving forward, and repeated, to generate the highest AGC.
Its also possible to shunt the AGC across the 0.047 uF cap at the tube grid
connections,
and keep the input signal low, and then tune for the highest AGC voltage
or detector voltage.
This method avoids connecting a lead via a cap to the anode of the mixer with a 455
kHz signal applied,
since such a connection upsets the C of the first IF, and mistunes it.

The shunted AGC allows the RF, mixer and IF tubes to operate with high gain
so to stay away from over load, the input signal should be low.

Using a modulated IF signal with 95% modulation with 100 Hz is a good idea,
because as the IF amp becomes overloaded either with negligible bias,
or with a lot of applied AGC, so to will the audio recovered.
I like to tune up old radios with a CRO attached and a high % of modulation,
and with AGC connected, because the set always works with it connected,
and when things are right, including the adjustment of R loading for the diode
detector,
there should be at least 5vrms of audio recovered from the detector.

This means about 28 volts peak to peak exist at the envelope
entering the diode detector, and maybe twice that
at the IF amp anode, if the IF transformer losses were 6 dB.
If the IF amp is a typical 6BA6 etc, and has idle Ia = 3 mA, and Ea = 200v
at the middle common AGC voltage, and ideal working point
for a load of say 50 kohms, then the load line analysis reveals about
300 volts peak to peak is the maximum voltage swing.
To cope with 100% modulation, the p-p modulation above and below the horizontal
axix is 150v, and peak modulation = 75v, so there is 53 vrms theoretically
available if the IF amp was fairly linear, which is won't be, ever, even if its a
sharp
cut off pentode and not the usual remote cut off type commonly used.
At such high output voltages, the IF amp becomes quite distorted, and
its clearly seen on the the audio recovered from the detector.

Many old radios produce about 3 vrms average audio signal at their detectors, and
the IF amp isn't working too hard, and the contribution to the set's thd by the IF
tube isn't too high.




An interesting experiment on a set that takes the AGC from the IFT primary
is to short the secondary of the IFT with a clip lead, you will observe an
increase in AGC voltage when the secondary is shorted, this is the same
effect that causes the dip in primary voltage when properly tuned.


I have not tried that, but common sense tells me that a shorted IFT sec
will reduce the load seen by the IF amp severely, and reduce the envelope amplitute
at the IFT pri,
or the tube anode, and thus generate less AGC, despite the increase in GM of all
the tubes subject to
AGC control.
What happens depends on the number of preceeding stages and the gain
reaction to AGC.

Patrick Turner.



Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/


  #53   Report Post  
John Byrns
 
Posts: n/a
Default

In article , Patrick Turner
wrote:

John Byrns wrote:

In article , Patrick Turner
wrote:

But there is rarely a dip in the tuning character of most AM sets.


That was my point and is the reason sets with a tuning eye virtually
always connect the tuning eye to the audio detector, not to the AGC
rectifier.


It may not be critical where you connect the feed to the magic eye in many old
radios.


Then why is the eye tube always connected to the audio detector and not
the AGC rectifier? Connecting it to the audio detector reduces the
modulation acceptance, so I was surprised when I first noticed that the
eye tube in a set I was looking at was connected to the audio detector,
and not the AGC rectifier where it wouldn't reduce the modulation
acceptance. I thought this was just a design blunder in the particular
radio I was looking at, so I looked up as many schematics as I could find
for eye tube radios with a separate AGC rectifier off the primary of the
IFT, and I was surprised to find that they all were wired the same way.
The only explanation that I can think of for this is that it is done so
the eye tube will provide a sharper tuning indication, without a possible
dip at the center.

But I often derive the AGC voltage separately from
a small cap&diode off the anode of the last IF amp, where more AGC

voltage is
available because the envelope amplitude is greater than at the

secondary of the
IFT.

The IFTs can be aligned with a VTM attatched to the AGC voltage,
and the tuning done to generate the highest AGC.


Good luck with this approach, it is likely to result in misalignment, this
sort of set should be aligned either with a modulated oscillator and audio
VTVM on the output, or by measuring the detector voltage.


It works, and its not neccesary to use a modulated carrier.
A carrier of exactly the 455 kHz can even be cap coupled via 10 pF

applied to the
antenna terminal
with the set tuned as low as it will go, and the IF tuned up starting on

the last
IF and
moving forward, and repeated, to generate the highest AGC.
Its also possible to shunt the AGC across the 0.047 uF cap at the tube grid
connections,
and keep the input signal low, and then tune for the highest AGC voltage
or detector voltage.


But this will cause miss tuning of the last IFT when the set uses a
separate AGC rectifier connected to the primary of the transformer, as a
result of the dip in the primary response.

An interesting experiment on a set that takes the AGC from the IFT primary
is to short the secondary of the IFT with a clip lead, you will observe an
increase in AGC voltage when the secondary is shorted, this is the same
effect that causes the dip in primary voltage when properly tuned.


I have not tried that, but common sense tells me that a shorted IFT sec
will reduce the load seen by the IF amp severely, and reduce the

envelope amplitute
at the IFT pri,
or the tube anode, and thus generate less AGC,


But this is one of those situations where "common sense" is wrong, and was
the first amazing lesson I learned from an early mentor, a lesson I have
never forgotten. Try it, connect the primary of an IF transformer to some
kind of impedance measuring device like an RX meter and see what the
primary impedance looks like with and without the secondary shorted. If
the primary and secondary Qs are the same and if the coupling is critical
the primary resistance will double when the secondary is shorted, if the
coupling is not critical the primary resistance will change by a factor
other than 2 X.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/
  #54   Report Post  
Frank Dresser
 
Posts: n/a
Default


"John Byrns" wrote in message
...
[snip]


Then why is the eye tube always connected to the audio detector and not
the AGC rectifier?


[snip]

The Radiotron Designer's Handbook 3 (p. 225) brings up this topic.
Basically they say, in radios with simple AVC seperated from the audio
detector, it's preferable to connect the eye tube to the AVC line. If the
radio uses delayed AVC, it's preferable to connect the eye tube to the audio
detector (through a decoupling network) if eye tube action is wanted on weak
signals.

Frank Dresser




  #55   Report Post  
John Byrns
 
Posts: n/a
Default

In article ,
"Frank Dresser" wrote:

"John Byrns" wrote in message
...
[snip]


Then why is the eye tube always connected to the audio detector and not
the AGC rectifier?


[snip]

The Radiotron Designer's Handbook 3 (p. 225) brings up this topic.
Basically they say, in radios with simple AVC seperated from the audio
detector, it's preferable to connect the eye tube to the AVC line. If the
radio uses delayed AVC, it's preferable to connect the eye tube to the audio
detector (through a decoupling network) if eye tube action is wanted on weak
signals.



Good point, I forgot about that aspect of the problem, which of course
also applies to delayed AGC developed off the audio detector diode. I
can't remember whether or not I was checking for delayed AGC when I was
rummaging through the schematics of eye tube radios to see if I could find
any where the eye tube was connected to the AGC line and the AGC rectifier
was connected to the IFT primary. Delayed AGC seems relatively uncommon
however.

Does anyone know of any examples of eye tube radios that take the AGC from
the IFT, without delay, and have the eye tube connected to the AGC line?


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/


  #56   Report Post  
Steven Swift
 
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Jeffrey D Angus writes:

Now appearing on alt.binaries.pictures.radio


Syncrhodyne three tube receiver from the April 1951 edition of
Radio News.


Jeff


Did anyone actually see this schematic? I can't find it.

Steve.
--
Steven D. Swift, , http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA
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Syl's Old Radioz
 
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"Steven Swift" a écrit dans le message

Did anyone actually see this schematic? I can't find it.


Right he
http://techpreservation.dyndns.org/b...files/?C=N&O=A

Synchro-1 and -2.jpg

Syl


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