Jon Noring wrote:

Patrick Turner wrote:
Volker Tonn wrote:
Jon Noring schrieb:

In the last couple of years I've posted various inquiries to this and
related newsgroups regarding high-performance, tube-based AM (MW/BCB)
tuners, both "classic" and modern.

Have a look into the "Collins" S-series. These are state-of-the-art
tube sets 'til now. At least it's not the tubes alone but the fabulous
mechanical IF-filters giving outstanding results for a tube set.
Manuals with layout diagrams should be available on the web....

Since Mr Noring says he has regularly trawled the Net for everyone
else's expertise on AM reception, but got nowhere, because he's
still doin it, why doesn't he gird his loins and put his shoulder to
the task of learning all about AM and radio engineering as spelled
out so clearly in all the old text books, and then damn well build
his own perfect AM radio???

Thanks for sharing your frank coments. They are acknowledged.

The important thing is that the replies to my "trawling" have been
very informative, including yours Patrick, and are not only
benefitting me, but are benefitting many others who are following this
thread in real time.

Whether my trawling is successful or not for my purposes is immaterial
-- if I fail, I fail -- I don't fear failure as some do -- the
discussion is further adding to the information pool for the community
of those interested in some aspect of tube-based AM tuners, and in
that regards I think it has been successful. (With Google archiving
the newsgroups, this information is now being preserved, and is
searchable.)

I don't mind sharing whay I know, but you will be the one left to
decide what works or doesn't work, so you shoukld get away from the PC,
and ito the workshop to try out ideas mentioned in all the responses to your
query.
I for one haven't time for the R&D, but if I was more passionate about
good AM than I already am, it'd be to the workshop I would go,
armed with ideas, and solder on towards lower thd and more BW.



There are obviously two sides to the engineering of radio receivers:
1) the basic theory and the basic categories of design approaches
(which I am studying -- it helps in that back in 1974 I had the
equivalent of one years' worth of basic electrical engineering courses
at the University of Minnesota, which is now all coming back to me),
and 2) the real-world engineering of receivers/tuners, using real
rather than theoretical components, and the attendant compromises and
work-arounds which inevitably result.

I do agree with Patrick's implying that there is no such thing as a
"perfect radio". I am not seeking the "perfect radio", but a
modern-design tuner "kit" sufficiently meeting the various
requirements I have previously set forth. I believe once a good
design results, that PCB boards can be made, coils can be built by
someone or some company experienced in doing that (I mention coils
since that is the one component difficult to buy right off the shelf
-- thank god no one has to build their own tubes!), and the schematic
with detailed instructions and guidelines sold through diytube (as an
example.)

There already have been several excellent SS kit designs for decent AM
released by Oz makers
in past years, but its 35 years since any tube based kits were available.

Nobody seems to think it'd be commercially viable to present yet another
AM kit, because 90% of folks listen to FM.

So you are on your own wanting to make a kit design that could be sold,
and I wish you well with the prototyping of coils and circuits.




The target market for the "kit" are those who build their own tube-
based components for their audio system, and want every component to
be a high-performer, approaching audiophile-grade in performance (yes,
AM broadcasts are not "audiophile", but audiophiles want a tuner that
brings out the best in what is there in the signal.) They don't want
to spend their limited time building junk, they don't want to build a
Radio Shack beginners' crystal set. They want very good performance
(which is admittedly a "fuzzy" word), commensurate with their other
components. They just want the tuner kit not to be overly complicated
in design, to work if they follow the instructions and guidelines, and
to meet their (collective) expectations.

And these kit builders are not novices, either, at wielding a
soldering gun, and in chassis and cabinet design -- they are
mechanically- and electronically-inclined, and are now building
audiophile-grade amps and preamps from the many kits now out there. I
also believe that some of the vintage radio collectors, who are
experienced at restoring radios, will also take an interest in the AM
tube tuner kit. (For those who don't know, I'm now restoring a Philco
37-670 console, so I'm not exactly out-of-touch with the radio
collecting world.)

Based on my experience with building audiophile-grade tube amps and
plugging into that community, I think I've laid out pretty well what
they want and expect. Most are not going to become radio design
enthusiasts, they will not live and breathe tuners, building hundreds
of circuits on cake pans in their basement (and I am not disparaging
those who do!) They simply are going to listen to the tuner they
laboriously built from the kit, happy with its performance, and happy
for what they have learned about how radios work "under the hood", in
a general sense. Some will no doubt get the radio bug, and join the
people here, rescuing old radios from the landfill, and restoring
them.

Maybe my focus on TRF-based designs and "channel-based design" have
been diversions. But, from what I've read about real-world TRF designs
(John Byrns messages have been great here), a TRF-based design has
some nice attributes from the audiophile kit perspective, and there
are clever real-world solutions around the selectivity and gain
limitations of the "what's taught in textbooks" regarding basic TRF
design, as John Byrns and others have noted many many times, but which
seems to fall on deaf ears of those who believe that the best
high-performance receiver (however "high-performance" is defined)
*must* be super-het in basic design.

But obviously, the vast majority of commercial designs of
high-performance tube-based radio receivers from the mid 1930's to the
1950's are super-het designs, and many of them are great performers,
so I'll post a parallel message with another call for candidate radios
to inspire the AM tuner kit. After all, if one is to put together an
AM tube tuner kit, it makes a lot of sense to base it on a proven
design from the past -- why reinvent the wheel?

For example, diytube (at http://www.diytube.com/ ) has taken the
venerable Dynaco ST-35 amp design, modernized it some (and to further
improve its audiophile performance), and is now selling the PCB
board with schematics and instructions to diy audiophiles. it is an
excellent performer (I know firsthand -- it is a *very nice* sounding
amp.) diytube is now working on a high-power monoblock tube amp kit
based on the Eico EL34 amp of old -- can't wait until it is released.

Just some thoughts...

Jon Noring

We await with ardent expectations of the fruit of your your efforts in your
workshop
with a saleable prototype tube based AM radio tuner kit.


Patrick Turner.