"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Patrick Turner" wrote in message
...
I post the schematic for the cathode follower buffer after the last
IFT
winding,
followed by an AM detector using germanium diodes used for generating
negative AVC voltage
and a positive going audio voltage, with no AC coupled loading on the
detector,
and with a final CF buffer direct coupled to the detector.

This circuit is able to produce a low distortion detected signal at
any
audio level up to at least 10vrms, and at any value of modulation %
below 100%.

Patrick Turner.


Is it such a good idea to use a Ge diode, with a breakdown voltage of
about 30 to 75V, on the output of a tube that has a peak to peak voltage
swing of well over a hundred volts?

IN the radios I have used germanium diodes, there has not been a single
failure in years of use.

I think its OK to use such a device even though the V might rise above the
breakdown voltage, because its in a circuit where the current resulting from
the over voltage
avalanche is very limited; there is only 270 pF to 0V and a 1M resistor.
But one could well use something like a silicon IN914
To avoid over voltaging, it would be possible to
arrange the CF tube so that its B+ is no more than +100v,
so that the cathode can't go more than about 100v positive.

That would be quite plenty of B+ to be able to still get about 4 vrms of
audio voltage
from a 100% modulated carrier from the detector, which is all you need,
ever,
to drive the audio amp.
Think backwards from where the 4 vrms audio comes from.

If you have 4v rms audio, this means 5.6 pv, so that is 11.2 p-p for the
modulation
envelope, and where there is 100% modulation, two modulation
envelopes are present, 180 degrees out of phas, so the total signal level is
22.4 v p-p.
The RF carrier envelope is 11.2v peak to peak without any modulation.
The input grid voltage of the CF is at +50v at idle,
and the 12AU7 cathode will be at say +54 v,
and if a non modulated carrier appears of 11.2v p-p, this will cause a rise
in the
positive detected steady voltage at the 270 pF of 5.6v, so the +ve voltage
at the 270 pF would sit at around 59v, and still allow a rise of nearly 35
vpk.
Then if you have 100 % modulation, this +59v measurement won't change
because the audio voltage swings up 5.6 pV and down 5.6 pV.

In the case of the AVC voltage diode, if you have 11.2v p-p of carrier,
modulated or not,
you will generate about -5.6v negative voltage at the 33 pF cap.

Now this may or may not be the ideal AVC voltage which will control the gain

in the various RF, mixer, and IF amps along the way.
Some receivers generate maybe -20v of AVC voltage, which is huge, and
indicates
that the carrier levels being amplified by the last IF amp tube must indeed
be on the high side,
and unfortunately, so will the thd/imd of the amplifying involved,
so I think careful setting up of the whole darn radio to make sure the
last IF amp produces no more than an adequate output is mandatory for
low thd/imd, and also low noise.
Perhaps a DV amplifier to boost the effect of the AVC voltage
is not such a bad idea, and using a darlington pair connected pair of PNP
transistors is one way to achieve this.
Such a pair of transistors can easily be set up from a negative bias voltage
of a few mA.
and an emitter resistor used to keep the DV gain perhaps as low as only 10,
and to keep the input impedance so high as to be able to be powered from the

2.2M resistor output from the AVC circuit shown in my schematic.
The dynamic range of AVC volts could then be +/- 50v from an input of +/-
5v.
Using a tube for this is a waste of glassware, and its good to see a
transistor
being a dumb slave for the tube's operating conditions.
It means extremely weak signals will have the AVC reduced to a minimum,
and very strong signals have the gain backed off more than with no DV amp.

In my wider than average IF bw radios due to R loading of the IF LC circuits
with 100k,
the gain of the mixer and IF amp is reduced, since gai = Gm x RL.

With less gain, the AVC control is reduced for between strong and weak
signals.
Here we have 300w stations sitting close to 5,000 w stations, and
no matter where you are in this city, a little help from a DV amp to
provide my dynamic volume control wouldn't go astray.

Patrick Turner.

"Patrick Turner" wrote in message
...


"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

[snip]

Thanks for the (very) full discourse.

Using a tube for this is a waste of glassware,

Actually, IMHO, I think that's true for the whole radio. ;-)


[snip]

Patrick Turner.

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Patrick Turner" wrote in message
...


"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

[snip]

Thanks for the (very) full discourse.

Using a tube for this is a waste of glassware,

Actually, IMHO, I think that's true for the whole radio. ;-)

Not if you have a few hundred tubes reclining gracefully around the
workshop lookin beautiful,
and wantin a socket to hop into;-0

Patrick Turner.




[snip]

Patrick Turner.

Patrick Turner wrote:

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:


"Patrick Turner" wrote in message
...


"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

[snip]

Thanks for the (very) full discourse.


Using a tube for this is a waste of glassware,

Actually, IMHO, I think that's true for the whole radio. ;-)


Not if you have a few hundred tubes reclining gracefully around the
workshop lookin beautiful,
and wantin a socket to hop into;-0

Yeah, I'd probably install sockets in a chassis, hook up the filament
pins, and put an on/off switch on the filament supply. Then let the
toobs hop into the sockets just for looks, and make the rest out of
solid state devices.

Just flip on that switch in the winter to keep the hearth fires glowing.
;-)

Patrick Turner.
[snip]
Patrick Turner.

"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Patrick Turner wrote:

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:


"Patrick Turner" wrote in message
...


"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

[snip]

Thanks for the (very) full discourse.


Using a tube for this is a waste of glassware,

Actually, IMHO, I think that's true for the whole radio. ;-)


Not if you have a few hundred tubes reclining gracefully around the
workshop lookin beautiful,
and wantin a socket to hop into;-0

Yeah, I'd probably install sockets in a chassis, hook up the filament
pins, and put an on/off switch on the filament supply. Then let the
toobs hop into the sockets just for looks, and make the rest out of
solid state devices.

That'd be like having wooden models at the artists class,
( or somewhere else I cannot mention on this family orientated news group )




Just flip on that switch in the winter to keep the hearth fires glowing.
;-)

Keep the home triodes burning, I say.

Just as well they can sing OK, or nobody would bother ;-]

Patrick Turner.

"Patrick Turner" wrote in message
...


"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Patrick Turner wrote:

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:


"Patrick Turner" wrote in message
...


"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

[snip]

Thanks for the (very) full discourse.


Using a tube for this is a waste of glassware,

Actually, IMHO, I think that's true for the whole radio. ;-)


Not if you have a few hundred tubes reclining gracefully around
the
workshop lookin beautiful,
and wantin a socket to hop into;-0

Yeah, I'd probably install sockets in a chassis, hook up the
filament
pins, and put an on/off switch on the filament supply. Then let the
toobs hop into the sockets just for looks, and make the rest out of
solid state devices.

That'd be like having wooden models at the artists class,
( or somewhere else I cannot mention on this family orientated news
group )

Just flip on that switch in the winter to keep the hearth fires
glowing.
;-)

Keep the home triodes burning, I say.

Yeah, that, too.

Just as well they can sing OK, or nobody would bother ;-]

A lady at work said she had to go to court to take care of her problem.
The city's Lawn Police came by (she thinks a neighbor complained) and
found that her lawn was turning brown from lack of water. Well, duh,
she was trying, she said, to get it so that they could replant it, or
whatever (her excuse anyway). So she had to pay a fine, like a parking
ticket.

What's this got to do with the thread above? Well, someday the cities
or municipalities may have an energy police, who come around with an IR
camera and look at your property and find that you're using excessive
energy. The narc cops already do this with pot growers, and find the
high electricity useage of the indoor grow lights. Imagine getting a
ticket for having a stereo that is using excessive energy(!) ;-))

Patrick Turner.

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

"Patrick Turner" wrote in message
...

"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:

Patrick Turner wrote:

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:


"Patrick Turner" wrote in message
...


"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote:

[snip]

Thanks for the (very) full discourse.


Using a tube for this is a waste of glassware,

Actually, IMHO, I think that's true for the whole radio. ;-)


Not if you have a few hundred tubes reclining gracefully around
the
workshop lookin beautiful,
and wantin a socket to hop into;-0

Yeah, I'd probably install sockets in a chassis, hook up the
filament
pins, and put an on/off switch on the filament supply. Then let the
toobs hop into the sockets just for looks, and make the rest out of
solid state devices.

That'd be like having wooden models at the artists class,
( or somewhere else I cannot mention on this family orientated news
group )

Just flip on that switch in the winter to keep the hearth fires
glowing.
;-)

Keep the home triodes burning, I say.

Yeah, that, too.

Just as well they can sing OK, or nobody would bother ;-]

A lady at work said she had to go to court to take care of her problem.
The city's Lawn Police came by (she thinks a neighbor complained) and
found that her lawn was turning brown from lack of water. Well, duh,
she was trying, she said, to get it so that they could replant it, or
whatever (her excuse anyway). So she had to pay a fine, like a parking
ticket.

What's this got to do with the thread above? Well, someday the cities
or municipalities may have an energy police, who come around with an IR
camera and look at your property and find that you're using excessive
energy. The narc cops already do this with pot growers, and find the
high electricity useage of the indoor grow lights. Imagine getting a
ticket for having a stereo that is using excessive energy(!) ;-))

Patrick Turner.

Our Prime Minister, John Howhard recently introduced a pilot scheme here
to tax the people's enjoyments, and a squad of brown clad tax inspectors
roam
the city to impose on the spot tax bills for people in their leisure time,
which John thinks they shouldn't really have because the lazy bustards
should be
at work on improving company profits by working harder, and to help pay the
costs
of running Oz like another state of the US.

A dude with a smile on his face was pulled up in the town square here the
other night.
"What's that bulge in your pocket sir?" goes the officer.
"A k-k-k- KT88, s-s-s- sir.." goes the dude, his smile fading.
" Do you realise you were in public, and smiling, AND with a KT88
enclosed in your left trouser recepticle?"
"W-w-w-well yes..."

The officer then proceeded to hand the dude a "pleasure tax bill" or PTB of
$250.

The new officers come from the latest new goverment office,
the Dept Of Pleasure and Entertainment,
or D.O.P.E.

Patrick Turner.

On Sat, 10 Jul 2004 11:02:05 +1000, Patrick Turner
wrote:

[snip]
Our Prime Minister, John Howhard recently introduced a pilot scheme here
to tax the people's enjoyments, and a squad of brown clad tax inspectors
roam
the city to impose on the spot tax bills for people in their leisure time,
which John thinks they shouldn't really have because the lazy bustards
should be
at work on improving company profits by working harder, and to help pay the
costs
of running Oz like another state of the US.

A dude with a smile on his face was pulled up in the town square here the
other night.
"What's that bulge in your pocket sir?" goes the officer.
"A k-k-k- KT88, s-s-s- sir.." goes the dude, his smile fading.
" Do you realise you were in public, and smiling, AND with a KT88
enclosed in your left trouser recepticle?"
"W-w-w-well yes..."

The officer then proceeded to hand the dude a "pleasure tax bill" or PTB of
$250.

The new officers come from the latest new goverment office,
the Dept Of Pleasure and Entertainment,
or D.O.P.E.

Patrick Turner.




I hope that this is really a joke. But I've been in Australia,
Melbourne, where they were still handing out citations for keeping
your business open on Saturday afternoon or Sunday.

But I liked the reference to KT88 ;-) Used those in one of my last
toooooooob amplifiers, back in 1960 ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

Jim Thompson wrote:

On Sat, 10 Jul 2004 11:02:05 +1000, Patrick Turner
wrote:

[snip]
Our Prime Minister, John Howhard recently introduced a pilot scheme here
to tax the people's enjoyments, and a squad of brown clad tax inspectors
roam
the city to impose on the spot tax bills for people in their leisure time,
which John thinks they shouldn't really have because the lazy bustards
should be
at work on improving company profits by working harder, and to help pay the
costs
of running Oz like another state of the US.

A dude with a smile on his face was pulled up in the town square here the
other night.
"What's that bulge in your pocket sir?" goes the officer.
"A k-k-k- KT88, s-s-s- sir.." goes the dude, his smile fading.
" Do you realise you were in public, and smiling, AND with a KT88
enclosed in your left trouser recepticle?"
"W-w-w-well yes..."

The officer then proceeded to hand the dude a "pleasure tax bill" or PTB of
$250.

The new officers come from the latest new goverment office,
the Dept Of Pleasure and Entertainment,
or D.O.P.E.

Patrick Turner.




I hope that this is really a joke. But I've been in Australia,
Melbourne, where they were still handing out citations for keeping
your business open on Saturday afternoon or Sunday.

But I liked the reference to KT88 ;-) Used those in one of my last
toooooooob amplifiers, back in 1960 ;-)

I guy recently got caught with a pair of 211, one in each pocket,
with a real big smile, and he got a tax bill for $1,000.

Nowdays no small business can survive without being open all weekend.

They hand out "citations" as you call them for staying at home on weekends
and being lazy.

Patrick Turner.