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 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:

On Tue, 08 Jun 2004 03:04:27 GMT, Jon Noring wrote:

I'm very interested in building such a tuner to match with
audiophile-grade tube amplifiers and pre-amplifiers now being built by
hobbyists (as well as those sold by commercial vendors.) There are
quite a few nice kits now being marketed for audiophile quality tube
amps/pre-amps, such as those made by diytube (http://www.diytube.com/
-- there are many others like diytube.) So why not similar kits (or
workable designs) for a tube-based AM tuner?

No offence Jon, but I think you're nuts. Most hifi listeners (never
mind audiophiles) wouldn't dream of using *FM* for serious listening,
because of the level of optimodding and other sound processing that
goes on. Quite a lot of commercial stations even adjust the playback
speed of their music to make the station sound more 'lively' and to
squeeze in more commercials.

AM has all that, plus very high levels of signal compression and an
effective HF cutoff of about 3.5kHz. You can't improve this by
extending the IF bandwidth, because the stations just don't transmit
anything above this.

There's nothing wrong with building your own high quality AM tuner,
either solid state or tube, but no matter how many gold lettered
Telefunken ECC83s you use it won't sound very good.

Best regards, Paul
--
Paul Sherwin Consulting http://paulsherwin.co.uk

Paul Sherwin wrote:

On Tue, 08 Jun 2004 03:04:27 GMT, Jon Noring wrote:

I'm very interested in building such a tuner to match with
audiophile-grade tube amplifiers and pre-amplifiers now being built by
hobbyists (as well as those sold by commercial vendors.) There are
quite a few nice kits now being marketed for audiophile quality tube
amps/pre-amps, such as those made by diytube (http://www.diytube.com/
-- there are many others like diytube.) So why not similar kits (or
workable designs) for a tube-based AM tuner?

No offence Jon, but I think you're nuts. Most hifi listeners (never
mind audiophiles) wouldn't dream of using *FM* for serious listening,
because of the level of optimodding and other sound processing that
goes on. Quite a lot of commercial stations even adjust the playback
speed of their music to make the station sound more 'lively' and to
squeeze in more commercials.

All the audiophiles I know do listen fervently to the FM stations we have
which
take pains to transmit unadulterated audio.
Where I am is a city of only 300,000, and we have
an Arts FM station funded by subcribers and mild advertisers, and their
signal is tops.
The govt owned station, ABC Classic FM broadcasts nothing but
classical and some jazz. Electric guitars are rarely heard.
They regularly do live broadcasts each sunday and during the week,
and all are at a high technical standard.
Then we have a community FM radio station run by feminists
and mainly leftists, and that has the best specialist rythym and blues
shows.
Then there is a station for ethnic culturists.

The remaining stations are pop music, christian, or sports report based,
and thir
programmes are all just ****e to me, and the audio is little better than
the AM stations,
and I am allergic to ALL their adverts, which have the opposite effect on
me that the advertisers hope for,
ie, I WILL NOT buy coca cola after hearing an add saying things go better
with coke.


AM has all that, plus very high levels of signal compression and an
effective HF cutoff of about 3.5kHz. You can't improve this by
extending the IF bandwidth, because the stations just don't transmit
anything above this.

Here in Oz, they do transmit more than 3.5 kHz of audio,
so we get some stations worth listening to.

There's nothing wrong with building your own high quality AM tuner,
either solid state or tube, but no matter how many gold lettered
Telefunken ECC83s you use it won't sound very good.

There are programs where the content has little above 8 kHz.
If one stretches the BW of the receiver here in Oz,
its surprising how good AM radio can sound.

A Telefunken ECC83 is a useless tube in any RF circuit.
I get your point, but ppl in r.a.t are spread around the globe
where different conditions prevail.

Patrick Turner.



Best regards, Paul
--
Paul Sherwin Consulting http://paulsherwin.co.uk

Paul Sherwin wrote:
Jon Noring wrote:

I'm very interested in building such a tuner to match with
audiophile-grade tube amplifiers and pre-amplifiers now being built
by hobbyists (as well as those sold by commercial vendors.) There are
quite a few nice kits now being marketed for audiophile quality tube
amps/pre-amps, such as those made by diytube (http://www.diytube.com/
-- there are many others like diytube.) So why not similar kits (or
workable designs) for a tube-based AM tuner?

No offence Jon, but I think you're nuts.

No offense is taken, and yes I may be a little nuts. :^)


Most hifi listeners (never mind audiophiles) wouldn't dream of using
*FM* for serious listening, because of the level of optimodding and
other sound processing that goes on. Quite a lot of commercial
stations even adjust the playback speed of their music to make the
station sound more 'lively' and to squeeze in more commercials.

Nevertheless, there are those hifi/audiophile listeners, such as
myself, who still wish to connect both AM and FM tuners to their audio
system, to listen to various broadcasts. Not everything audio is found
on CD/vinyl.

On FM, especially among alternative FM stations, one often finds very
unusual musical programs being broadcast of music which the listener
does not have in their collection (it helps them to expand their
horizons and maybe go out and purchase said music on CD/vinyl.) In
addition, there are sometimes live broadcasts of concerts which will
never appear on CD/vinyl. (In Salt Lake City, the alternative FM
station I am thinking of is KRCL, http://www.krcl.org/ . Really a fun
station to listen to, especially the late Sunday night program
broadcasting 1920's to 1940's era recordings.)

On AM there are certainly broadcasts which interest different people
for different reasons at different times. Live sports events not found
elsewhere, news, of course the venerable talk radio, and for some of
us, we like to spin the dial at night and see what distant stations we
can pull in.

Thus, if we do connect AM and FM tuners to our system, we want the
tuners to deliver the highest audio quality signal to our amplifiers.
That is, the tuners should not taint the broadcast signal any more
than it already is tainted as it leaves the broadcaster's antenna.

(Btw, aren't there alternative FM stations which do not play these
games of distorting the sound, and only broadcast the purest possible
signal?)


AM has all that, plus very high levels of signal compression and an
effective HF cutoff of about 3.5kHz. You can't improve this by
extending the IF bandwidth, because the stations just don't transmit
anything above this.

Well, maybe in the U.S. most stations cutoff at 3.5khz. Then that's
where they cutoff. However, the AM tuner design is intended for the
world, and as Patrick Turner noted, in Australia many broadcasters
have a much higher rolloff because of the "open highway" they have
on the BCB -- fewer stations spread farther apart.


There's nothing wrong with building your own high quality AM tuner,
either solid state or tube, but no matter how many gold lettered
Telefunken ECC83s you use it won't sound very good.

Agreed in principle. The AM tuner must deliver the highest possible
fidelity as broadcast, that's all. It must have very low distortion.

One question to ask is in various areas of the world (including the
U.S.) what is the distribution of HF cutoff among the many broadcast
stations? I doubt in the U.S. every broadcaster rolls off HF at
3.5khz, but maybe most do -- are there any AM stations in the U.S.
which have a much higher HF rolloff than 3.5khz? Note again Patrick's
comment on Australian AM broadcasters.

Jon Noring

On Tue, 08 Jun 2004 14:45:41 GMT, Jon Noring wrote:

On FM, especially among alternative FM stations, one often finds very
unusual musical programs being broadcast of music which the listener
does not have in their collection (it helps them to expand their
horizons and maybe go out and purchase said music on CD/vinyl.) In
addition, there are sometimes live broadcasts of concerts which will
never appear on CD/vinyl. (In Salt Lake City, the alternative FM
station I am thinking of is KRCL, http://www.krcl.org/ . Really a fun
station to listen to, especially the late Sunday night program
broadcasting 1920's to 1940's era recordings.)

It's very true that the level of audio postprocessing varies a great
deal around the world. In the UK all FM commercial broadcasters use
very high levels of compression (including Classic FM, a national
classical music station) because they like to sound 'loud'. Only the
BBC's classical station uses reasonable levels of compression and
limiting. This heavy compression is also used on digital feeds, where
it is completely unnecessary.

On AM there are certainly broadcasts which interest different people
for different reasons at different times. Live sports events not found
elsewhere, news, of course the venerable talk radio, and for some of
us, we like to spin the dial at night and see what distant stations we
can pull in.

Yes Jon, but that's not audiophile listening, it's using radio as it's
always been used for 80 years. You would do just as well to plug a
1970s Grundig Yacht Boy into your system (which is what I do :-) )

Well, maybe in the U.S. most stations cutoff at 3.5khz. Then that's
where they cutoff. However, the AM tuner design is intended for the
world, and as Patrick Turner noted, in Australia many broadcasters
have a much higher rolloff because of the "open highway" they have
on the BCB -- fewer stations spread farther apart.

Modern AM transmitters have a very sharp rolloff above a certain
frequency. Broadcasting above this would just waste transmitter power,
since (almost all) radios wouldn't be able to receive it because of
their IF selectivity characteristics. The 9kHz or 10kHz AM channel
width is just a convention, but once it has been adopted there's no
point in trying to receive a wider bandwidth - you'll just get
interference from adjacent stations.

There's nothing wrong with building your own high quality AM tuner,
either solid state or tube, but no matter how many gold lettered
Telefunken ECC83s you use it won't sound very good.

Agreed in principle. The AM tuner must deliver the highest possible
fidelity as broadcast, that's all. It must have very low distortion.

One question to ask is in various areas of the world (including the
U.S.) what is the distribution of HF cutoff among the many broadcast
stations? I doubt in the U.S. every broadcaster rolls off HF at
3.5khz, but maybe most do -- are there any AM stations in the U.S.
which have a much higher HF rolloff than 3.5khz? Note again Patrick's
comment on Australian AM broadcasters.

In the US and Canada, AM stations are allocated 10kHz bandwidth,
giving a theoretical 5kHz treble cutoff. In most other place that's
9kHz/4.5kHz. Stations transmit a more restricted frequency range than
this though, for a number of technical reasons. That's where my rough
and ready 3.5kHz figure came from.

Best regards, Paul
--
Paul Sherwin Consulting http://paulsherwin.co.uk

"Paul Sherwin"

In the US and Canada, AM stations are allocated 10kHz bandwidth,
giving a theoretical 5kHz treble cutoff. In most other place that's
9kHz/4.5kHz. Stations transmit a more restricted frequency range than
this though, for a number of technical reasons. That's where my rough
and ready 3.5kHz figure came from.

Best regards, Paul


** In Australia the AM channel spacing goes in 9 kHz increments, however
the transmitted bandwidth is not affected by that fact since the authorities
have kept a wide frequency separation between transmitters serving the same
areas.

The recovered audio from many transmitters is of good quality on speech
and music with high frequencies extending to 12 kHz in some cases - the
government owned networks being the best in this regard. At night, far
distant adjacent channel signals can produce an audible 9 kHz background
whistle which a sharp notch filter deals with most effectively. I use an
Australian made valve AM tuner designed for hi-fi reception of local
broadcasts and have tried out a few SS hi-fi AM designs as well.

The secret of good AM reception is the use of a balanced loop or frame
antenna to reduce man made and static noise to insignificance.



............ Phil