"Jon Noring" a écrit dans le message

...high-performance, tube-based AM (MW/BCB)

I'm very interested in building such a tuner to match with
audiophile-grade tube amplifiers and pre-amplifiers ...

Audiophile AM is an oxymoron...

Syl

Syl's Old Radioz wrote:

"Jon Noring" a écrit dans le message

...high-performance, tube-based AM (MW/BCB)

I'm very interested in building such a tuner to match with
audiophile-grade tube amplifiers and pre-amplifiers ...

Audiophile AM is an oxymoron...

Syl

If the audio on a CD is not all used to modulate the AM carrier,
it could be said it ain't hi-fi, and 5 kHz bandwidth or less is
certainly not hi-fi.
But there is reason for those who build gear for the fun to try
to make the receiver as good as possible.
If 5 kHz is all we get, all the more reason to reduce thd to a minimum.

FM only goes to 16 kHz, and the audio information to
get the difference between L and R channels is contained on a
subcarrier signal of 38 kHz.

Unfortunately, our predecessors thought 16 kHz was plenty bandwidth.
It would have been nicer to have 20 kHz, and a 70 kHz subcarrier,
but then you couldn't have so many subcarriers as we do now,
which is one at 38 kHz, then another at 76 kHz, and another at 96 kHz,
so that several extra information channels can be carried on the one
signal transmitted between 88 and 108 mHz.

Fidelity was always going to suffer from the forseeable desire for
channels.

The AM mid wave band radio spectrum could have a lot more fidelity if we
had stations
separated by 40 kHz instead of 10 kHz. But commercial interests were
always going to
put fidelity last, and profits first.

Now there's talk of digital broadcast, and the phasing out of FM and AM
broadcasting.
But I don't expect it to dissappear soon, and even more channels for
people's attention seem
to spring up daily to consume the leisure time of the masses,
and TV gets the main share.
Digital recievers need to be costed below the existing radio receiver
costs before
folks will buy them as an add on for their TV watching.
People's expectations about home entertainment are far beyond
just sitting down listening to music.
Most AM is listened to in cars, if at all, but usually while folks are
doing something else.
There will always be broadcasting of some sort, because its possible,
and the spectrum exists, but the programme quality decline continues.
As fewer listeners tune in, there are less advertisers willing to pay
the stations,
and its not worthwhile building a super dooper radio to listen to them.

I have 3 HRO receivers in parts from which I plan to get two good ones,
I have several other radio projects to do, but alas no time, since I
have to work for
a living.

I'd like to try using a 2 MHz IF strip for my A radio, because at least
there
3 stations here worth listening to out of the total of 7.

I figure the 2 MHz IF frequency would allow
a Q of 50 for each LC circuit, and thus the BW would be 40 kHz for each,

so with 4 or 6 consecutive LC circuits the BW could be 20 kHz,
thus allowing 10 kHz of audio BW.
Perhaps single tuned IF coils are all that's needed.
The single tuned high Q IF auto tranny is pretty awful at 455 kHz, as
used in transistor
based circuits because with a Q of 100, the BW is only 4.55 kHz,
and with two such coils you have only say 3.6 kHz, so only 1.8 kHz of
audio can
pass, and many transistor radios have only 1.8 kHz of audio BW.
Some tube types only have that much. I have measured plenty
of impressive looking tube sets with RF stages, and the total number of
tuned circuits is
about 6 including 4 IF coils, and the bandwidth narrows down badly.

Communications radios sometimes used lower IF at say 100 kHz
to take advantage of the lower bandwidth for a given Q.
This allowed very good selectivity for short wave,
but was hopeless for local station AM.

Its possible that by removing many turns off existing 455 kHz IFTs,
the 2MHz could be achieved.

The oscilator would operate at the BCB frequencies + 2 MHZ.
So the oscillator coils and circuit would need revision, but then that'd
be easy,
since the coils do not differ much from the usual low end short wave
types.

The other way of doing an AM radio today is to use totally digital
techniques for converting what is coming from the antenna and pull out
the audio from
any wanted station in ways which nobody in 1935 could ever have
imagined.
I think this would be an interesting digital project for someone.

Everyone has a PC at home these days, and it sould be easy to
use it to sift out a few radio waves.

But if fidelity isn't transmitted, not even a PC can decide correctly
what to substitute for missing audio HF.


Just my 3c worth,

Patrick Turner.

Patrick Turner wrote:


Its possible that by removing many turns off existing 455 kHz IFTs,
the 2MHz could be achieved.

The oscilator would operate at the BCB frequencies + 2 MHZ.
So the oscillator coils and circuit would need revision, but then that'd
be easy,
since the coils do not differ much from the usual low end short wave
types.



A good set of ~2.8 MC IF transformers can be had in the 6-9.1 MC ARC-5
receivers.


Jeff Goldsmith

Patrick Turner wrote in message ...
Syl's Old Radioz wrote:

"Jon Noring" a écrit dans le message

...high-performance, tube-based AM (MW/BCB)

I'm very interested in building such a tuner to match with
audiophile-grade tube amplifiers and pre-amplifiers ...

Audiophile AM is an oxymoron...

Syl
Now there's talk of digital broadcast, and the phasing out of FM and AM
broadcasting.
But I don't expect it to dissappear soon, and even more channels for
people's attention seem
to spring up daily to consume the leisure time of the masses,
and TV gets the main share.
Digital recievers need to be costed below the existing radio receiver
costs before
folks will buy them as an add on for their TV watching.
People's expectations about home entertainment are far beyond
just sitting down listening to music.
Most AM is listened to in cars, if at all, but usually while folks are
doing something else.
There will always be broadcasting of some sort, because its possible,
and the spectrum exists, but the programme quality decline continues.
As fewer listeners tune in, there are less advertisers willing to pay
the stations,
and its not worthwhile building a super dooper radio to listen to them.

I have 3 HRO receivers in parts from which I plan to get two good ones,
I have several other radio projects to do, but alas no time, since I
have to work for
a living.

I'd like to try using a 2 MHz IF strip for my A radio, because at least
there
3 stations here worth listening to out of the total of 7.

I figure the 2 MHz IF frequency would allow
a Q of 50 for each LC circuit, and thus the BW would be 40 kHz for each,

so with 4 or 6 consecutive LC circuits the BW could be 20 kHz,
thus allowing 10 kHz of audio BW.
Perhaps single tuned IF coils are all that's needed.
The single tuned high Q IF auto tranny is pretty awful at 455 kHz, as
used in transistor
based circuits because with a Q of 100, the BW is only 4.55 kHz,
and with two such coils you have only say 3.6 kHz, so only 1.8 kHz of
audio can
pass, and many transistor radios have only 1.8 kHz of audio BW.
Some tube types only have that much. I have measured plenty
of impressive looking tube sets with RF stages, and the total number of
tuned circuits is
about 6 including 4 IF coils, and the bandwidth narrows down badly.

Communications radios sometimes used lower IF at say 100 kHz
to take advantage of the lower bandwidth for a given Q.
This allowed very good selectivity for short wave,
but was hopeless for local station AM.

Its possible that by removing many turns off existing 455 kHz IFTs,
the 2MHz could be achieved.

The oscilator would operate at the BCB frequencies + 2 MHZ.
So the oscillator coils and circuit would need revision, but then that'd
be easy,
since the coils do not differ much from the usual low end short wave
types.

The other way of doing an AM radio today is to use totally digital
techniques for converting what is coming from the antenna and pull out
the audio from
any wanted station in ways which nobody in 1935 could ever have
imagined.
I think this would be an interesting digital project for someone.

Everyone has a PC at home these days, and it sould be easy to
use it to sift out a few radio waves.

But if fidelity isn't transmitted, not even a PC can decide correctly
what to substitute for missing audio HF.


Just my 3c worth,

Patrick Turner.

I don't have 3c and I only have 2GB. WTF do I want to do that on this
POS. Why does 'radio' have to be done on a computer? Get moving and
build a dedicated device (radio) instead of using a damned computer.
This should be in a sci. group.

But if fidelity isn't transmitted, not even a PC can decide correctly
what to substitute for missing audio HF.


Just my 3c worth,

Patrick Turner.

I don't have 3c and I only have 2GB. WTF do I want to do that on this
POS. Why does 'radio' have to be done on a computer? Get moving and
build a dedicated device (radio) instead of using a damned computer.
This should be in a sci. group.

I don't expect anyone to pay 3c for what I say, which could be seen as OT.

I have already built a decent AM radio, and re-engineered an FM radio,
both to my own designs, so I feel OK about considering the alternatives
which might involve a PC.

Patrick Turner.

"Patrick Turner" a écrit dans le message

I don't expect anyone to pay 3c for what I say, which could be seen as OT.

You just met our village idiot it seems...

There is an unspoken rule here..._Ignore_ his posts. Let him talk to
himself.

We don't get into fight with village idiot like you do on RAT...Keeps rar+p
"clean"...;o)

Syl

Syl's Old Radioz wrote:

"Patrick Turner" a écrit dans le message

I don't expect anyone to pay 3c for what I say, which could be seen as OT.

You just met our village idiot it seems...

There is an unspoken rule here..._Ignore_ his posts. Let him talk to
himself.

We don't get into fight with village idiot like you do on RAT...Keeps rar+p
"clean"...;o)

Syl

Well, with all due respects to all gentlemen and possible idiots
on all groups to whom this subject thread is cross posted to,
I reserve the right to decide who I will ignore or not.

I will desperately try not step on anyone's toes as I act in well intentioned
freewill.

I won't budge from the idea that its possible to digitise the signal from the
antenna and simply apply
suitable algorithms, and get digital decoding, without all the phase shift
caused by consecutive tuned circuits.
Like on expensive CD players, a tubed output filter on the final DA converter
could be used,
and a decent sound could be had, at least in Oz, where the audio transmitted by
AM is often very
wide bandwidth, depite the fact that the networked stations send their radio
shows to air at different times,
and via satellite, before finally being broadcast by a local AM transmitter.
God knows how many links the signal goes through, afaik.

I have tried to address the problems caused by tuned circuit delays in
recommending
that 2 MHz IFTs be used.
I do think tubes are good for IF amps, certainly the last IF amp, because
of the huge dynamic range of the tubes, and far better performance
can be had compared to using j-fets and a lousy 12 volt B+ supply.
Some might argue silicon opamps would be better still.
I would have no objection to whatever they used, as long as it
achieves the goal of high quality sound, and it was a valid way of doing it, as
far as they were concerned.
But a j-fet balanced converter and first IF amp would be permissable
because the signals are so low before they get to a second and final IF amp.

To get ideal signal from an AM tubed receiver, the AF signal
from a 100% modulated AM IF carrier should be around 2vrms
at least, so the tube isn't working beyond its linear class A range.

Anyone have anything to say about this?

Patrick Turner.

Patrick Turner wrote:

I won't budge from the idea that its possible to digitise the signal
from the antenna and simply apply suitable algorithms, and get
digital decoding, without all the phase shift caused by consecutive
tuned circuits.

And I agree with Patrick. Despite my desire to have a nice, kit-made,
high-performance AM tube tuner, ultimately I think the best radio
tuner for sound quality and overall performance (whether AM, ASM, FM,
digital broadcast, etc.) is the pure digital system as described by
Patrick.

But do the necessary low-level A-D converters already exist? Is anyone
actually building radios on this principle, or are we still a few
years off?

Jon Noring

[p.s., pure Class D digital amps are continuing to improve, with
better switching and so on, so ultimately the only analog streams
we'll be dealing with will be radio signals captured by the antenna
(which will promptly be digitized), and the output to the speakers
from the last-stage PWM of the digital amplifier. Everything inbetween
will totally be digital, using advanced and inexpensive DSP to do
things not possible in the analog processing realm. The only realm
left for the audiophiles to play in will be speakers.)

In article ,
Patrick Turner wrote:

Syl's Old Radioz wrote:

"Patrick Turner" a écrit dans le message

I don't expect anyone to pay 3c for what I say, which could be
seen as OT.

You just met our village idiot it seems...

There is an unspoken rule here..._Ignore_ his posts. Let him talk
to himself.

We don't get into fight with village idiot like you do on
RAT...Keeps rar+p "clean"...;o)

Syl

Well, with all due respects to all gentlemen and possible idiots on
all groups to whom this subject thread is cross posted to, I reserve
the right to decide who I will ignore or not.

I will desperately try not step on anyone's toes as I act in well
intentioned freewill.

I won't budge from the idea that its possible to digitise the signal
from the antenna and simply apply suitable algorithms, and get
digital decoding, without all the phase shift caused by consecutive
tuned circuits.


Chill dude. There is nothing wrong with this idea and the current
technology can do it. The problem is money. It would be expensive to do
this and I would not expect people to pay the price when it would be a
small improvement over the current generation of radios. Heck, I would
not expect people to pay the price for a large improvement.

Digital techniques do not end all distortion and add there own type of
noise by the way.

--
Telamon
Ventura, California

Syl wrote:
Jon Noring wrote:

...high-performance, tube-based AM (MW/BCB)

I'm very interested in building such a tuner to match with
audiophile-grade tube amplifiers and pre-amplifiers ...

Audiophile AM is an oxymoron...

Yes, in a sense this is true if we look at it from the broadcast side
of things.

However, if an audiophile wants to add an AM tuner to their system
(such as listen to oldies, news, sports, talk radio, whatever), they
*want* to hear the broadcasts at the highest possible audio fidelity
of whatever is carried by the signal. (TRF looks especially intriguing
for the AM tuner design, which I hope John Byrns will comment on.)

Definitely, the AM tuner design must not get in the way. As Patrick
Turner noted, in Australia may of the broadcasters appear to take
advantage of having fewer stations and broadcast with higher audio
bandwidth (even though channel spacing is 9khz), so the AM tuner
should have the ability to handle that higher audio bandwidth and do a
great job at it. Variable bandwidth control is certainly indicated
(especially if the tuner will also be used for casual DXing, where the
bandwidth will need to be narrowed for resolving real weak stations.)

About volume control (as also noted by Patrick Turner), I'm not sure
if the AM tuner will need one if connected to a preamp. If it is to
connect directly to an amplifier, though, it will need a volume
control. Here, putting a "standard" passive preamp volume control at
the line out of the AM tuner is indicated, unless there is a reason
to place the volume control further upstream in the "chain."

Jon Noring


p.s., do join the YahooGroup 'am-tube-tuners' if this topic interests
you. If you already have a YahooID, you can subscribe to it via:

http://groups.yahoo.com/group/am-tube-tuners/

If you don't have a YahooID, send a blank email to: