John Doty wrote:

Telamon wrote:

Congratulations for the continuation of one of the most retarded
threads I've yet read. Never heard of biasing a diode or being unable
to understand doing so is pretty pathetic. Electronics does not get any
simpler than this.

John understands this stuff extremely well: I've argued detector issues
with him on rec.antiques.radio+phono in the past. John obviously doesn't
believe Patrick really understands what he's advocating.

I am not a university trained electronics engineer with a sound
backgound of mathematical ability.

But one doesn't need to understand a simple AM radio at the post graduate
level, complete with all the maths, to be able to build a set that works
better than nearly all the old junk I occasionally get to service or repair.

John has ofrten tested my ideas expressed here on the group, and I have never
minded that,
bearing in mind that one quick explanation to *all* readers may not be enough
to
provoke them into forming a clear mental picture of how they could
build a radio from scratch if they had to.


Biased diode envelope detectors are *not* simple: I've used them for
x-ray spectroscopy with scintillation counters, and they are tricky
beasts. A biased diode is far from an ideal switch: its dynamic
resistance varies with instantaneous signal level, making the circuit
bandwidth vary rapidly. The mathematics of this are rather difficult.

But your applications in X-ray spectroscopy and scintilation counting,
whatever that involves, may be somewhat different to an RF diode detector
circuit
where afaik diode detection is one heck of a simple concept, with very much
in common with a diode power rectifier.
The crystal diode detector works fine as a switch at 10.7 MHz in an FM
receiver discriminator circuit,
and 455 kHz is a doddle.

The math don't have to be known.

As I pointed out in another recent post, a comparison between the
AM envelope shape and the recovered audio can and should be made using
a dual trace oscilloscope, at low and high levels of signals, and at high and
low levels
of AM%, and at 20 Hz, 1 kHz, and 20 kHz of audio F modulation.
If the detector is then seen to be low thd with all tests, and no tube or
diode
is anywhere near an overloaded or over rated condition, then
you have the circuit working propoerly without having had to use
university standard maths.



I also think an emphasis on detector distortion under idealized test
conditions misses the real issues. The most annoying distortion on AM
signals doesn't come from the detector. Multipath, steep IF skirts, and
AGC all distort the modulation envelope. Perfect reproduction of such
distorted envelopes yields bad sound. I suspect that the great sound of
the old tube diode detectors actually results from their poor
reproduction of these sorts of envelope distortion (but this is a
difficult hypothesis to test).

I have built many tube amps and a few radios, and the better they measure,
the better they sound.
A wide bandwidth for the IF allows less critical tuning, so the distortion
effects
of an IFT or the front end being slightly off tune are negligible.



In any case, my 1934 Stromberg-Carlson 58-T, with its weak AGC, poor
skirt selectivity, and a classic diode detector has the best sound of
any of my AM radios, both to my ears and my wife's. One receiver it
beats is my Drake R-8, which uses a very low distortion (active full
wave rectifier) envelope detector. Of course, the R-8 is a much better
DX machine, but that's a different issue.

I have serviced dozens of old radios which came the the workshop much loved,
but some sounded quite dreadful for a variety of reasons in the
RF, mixer, IF detector and audio amps, not to mention the speaker.
I sometimes just repair these horrors, rather than modify them.

One spectaculary displeasing radio I was given is a 1957 Radiola with 7 bands
including the BCB,
and it included a tuning cap with 3 gangs, because an RF stage was included.
It was the deluxe radio model from that company, and even had a PP audio amp
with two 6V6 with FB, and a better than average 12" speaker.
It has proper active tone controls.
The tuner section gave a lousy 2 kHz of audio BW.
Turning up the treble boost did nothing; there is no treble to boost.
It was said that such radios sounded "mellow", and I dislike them intensly.
I have completely revised the circuit to my own, and now it sounds far
better,
with about 8 kHz of AF bw.
The SW performance isn't too good, and the alignments and tracking
are all very inaccurate, but I rarely if ever listen to SW.
One of these days I will build a cabinet for the Radiola chassis I have,
and build a speaker box.

Unlike the big Radiola, most old AM radios were designed to be cheap to make,

with a minimum of parts, and thus were slightly too simple for my way of
thinking,
or my ears.

When one extends the audio BW and reduces the thd from 5% to 1%,
then a good AM set sounds almost as good as thre same material being
broadcast on FM.

My kitchen radio has a full range speaker in a 60 litre reflexed box separate
from
the cabinet for the radio tuner and SET audio amp with NFB using one EL34.
I don't like the sound of a 6V6 with no FB powering a speaker with 6 kHz of
unflat bandwidth,
with the speaker mounted in a resonant cabinet with an open back and resonant
sides.

I don't like listening to distance AM stations, because the vast majority
transmit
programme material almost identical to what is available locally since
networked stations
have universally spread around the country, and the distance listening can
never be
without noises.

Patrick Turner.

I un-retarded this technical thread as a favor to rrs's Twains of Today, the
Modern Menckens and our Real Time Roykos.

Others are invited to follow along. However, I may miss much of it. To
paraphrase General Stonewall Jackson, I've killfiled 'em. Killfiled 'em
all.

Frank Dresser

Hey John,

How's the listening in the wild west? Did you get a decent antenna up?


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In article ,
Patrick Turner wrote:

John Doty wrote:

Telamon wrote:

Congratulations for the continuation of one of the most retarded
threads I've yet read. Never heard of biasing a diode or being unable
to understand doing so is pretty pathetic. Electronics does not get any
simpler than this.

John understands this stuff extremely well: I've argued detector issues
with him on rec.antiques.radio+phono in the past. John obviously doesn't
believe Patrick really understands what he's advocating.

I am not a university trained electronics engineer with a sound
backgound of mathematical ability.

Yeah, what a great pronouncement for a hobbyist news group after one
hundred posts of gobble de goop.

--
Telamon
Ventura, California

In article ,
John Doty wrote:

Telamon wrote:

Congratulations for the continuation of one of the most retarded
threads I've yet read. Never heard of biasing a diode or being unable
to understand doing so is pretty pathetic. Electronics does not get any
simpler than this.

John understands this stuff extremely well: I've argued detector issues
with him on rec.antiques.radio+phono in the past. John obviously doesn't
believe Patrick really understands what he's advocating.

Snip

All parties involved in this thread are being extremely thick in the
head. You can read into the discussion what you want but I see a
disregard of basic concepts.

If John knows better and is stringing a Patrick along don't you think a
better medium would be email?

Such discussions are endless and worthless in my opinion but if you feel
them entertaining have at it. I'd rather read a text book with a better
chance I'm not being misled in some way.

Like I said I'll comment again when the thread hits 500 which at the
rate its going should not be a problem. By all means have fun at three
news groups expense.

--
Telamon
Ventura, California

Telamon said:

Yeah, what a great pronouncement for a hobbyist news group after one
hundred posts of gobble de goop.

Like you offered useful information.
You don't seem to be bothered by crossposting yourself, either

--
Sander deWaal
Vacuum Audio Consultancy

Telamon wrote:

In article ,
John Doty wrote:

Telamon wrote:

Congratulations for the continuation of one of the most retarded
threads I've yet read. Never heard of biasing a diode or being unable
to understand doing so is pretty pathetic. Electronics does not get any
simpler than this.

John understands this stuff extremely well: I've argued detector issues
with him on rec.antiques.radio+phono in the past. John obviously doesn't
believe Patrick really understands what he's advocating.

Snip

All parties involved in this thread are being extremely thick in the
head. You can read into the discussion what you want but I see a
disregard of basic concepts.

If John knows better and is stringing a Patrick along don't you think a
better medium would be email?

Such discussions are endless and worthless in my opinion but if you feel
them entertaining have at it. I'd rather read a text book with a better
chance I'm not being misled in some way.

Like I said I'll comment again when the thread hits 500 which at the
rate its going should not be a problem. By all means have fun at three
news groups expense.

--
Telamon
Ventura, California

Again you prattle on like a miffed school girl about us and our interest
in tubed radios.

Neither John or myself have any intention of quitting our efforts.
We shall not be intimidated.

Let me know when you have something of substance to say about AM radio.

Patrick Turner.

"Frank Dresser" wrote in message ...
I un-retarded this technical thread as a favor to rrs's Twains of Today, the
Modern Menckens and our Real Time Roykos.

Others are invited to follow along. However, I may miss much of it. To
paraphrase General Stonewall Jackson, I've killfiled 'em. Killfiled 'em
all.

Frank Dresser

Musta killfiled 'em all. Good work! (I think?)

In article ,
Patrick Turner wrote:

Snip

Again you prattle on like a miffed school girl about us and our interest
in tubed radios.

Yeah I'm miffed about the cross posting not about you or your interests
but you are to thick in the head to get that.

Neither John or myself have any intention of quitting our efforts.

Well that's just the way Trolls are, they don't care about anybody.

We shall not be intimidated.

Sure thing. Have another Fosters and post away.

Let me know when you have something of substance to say about AM radio.

Why? You don't care what I think.

--
Telamon
Ventura, California

Telamon wrote:

Yeah I'm miffed about the cross posting not about you or your interests
but you are to thick in the head to get that.

There's nothing wrong with cross posting of messages that are on topic:
the designers of USENET intended it to be used in this way.

Of course, you could perhaps argue that this thread is only
superficially on topic in rec.radio.shortwave, since it's not about
brain dead political ideology, the real focus of the group. I suppose
you could make a similar objection to its presence in
rec.antiques.radio+phono since greed does not appear to motivate the
participants.

Personally, I find this thread interesting: envelope detectors are
fascinatingly subtle. How to make one that sounds good for real signals
remains poorly understood. To me it's more on topic than 95% of the
messages in these groups.

-jpd