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Old November 11th 11, 09:42 AM posted to rec.audio.tubes,rec.radio.shortwave
Patrick Turner Patrick Turner is offline
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First recorded activity by RadioBanter: Nov 2011
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Default Building a new shortwave tube radio

On Nov 11, 4:52*pm, wrote:
*With the survivalist market as well as the DIYers who would build a
kit I have given thought to the idea of building a new tube shortwave
receiver as a usable, practical set.


Most people who are into radio might think you are irrational, because
good short wave reception with tubes has been done by major
manufacturers of the past rather better than you can ever imagine to
achieve, unless you have far greater intelligence than their leading
chief designers wo passed lots of exams and universities and had
passed the test of being jolly good fellows in the real world of
private enterprise employment and marketing activities with the now
mentioned Racal, and Hammlund, Hallicrafters et all, just to name a
few.


*That means no regens, no DC bull****,


Regenerative boost I can understand, but "DC bull****" Such a term
does not appear in any electronic books written prior to 1960 when
tubed radio was regarded as the best mature technology for SW
reception.

and no plug in coils. It must
have production grade RF and IF coils, a bandswitch, and require
alignment. If sold as a kit the builder will need a RF generator and a
scope (or a spec an or CSM with a track gen).


You must be dreamin'. Its not clear at all what you want. Do you wanna
make a radio from scratch, or do ya wanna buy a kit made by some
sucker who is likely to find he'll sell 2 kits over 10 years, and get
a lousy price from YOU?

If ya wanna build just ONE HF receiver for you only, then there's
plenty of old books on making radios, just follow what you read in the
books, de-bug all what you build, as all the manufacturers have done
before you.
What happens first though? Do you die in ten years leaving behind a
mess to clean up and no working radio, or you get a working radio in 3
months, fairly well perfected, and live for 9 years and 9 mths to
enjoy it?

*It should use off the shelf parts even if those shelves are bare, as
it is better to copy an existing item than design from scratch. I
would clone the Eddystone dial mechanism and the bandswitch and coils
from some Hallicrafters or Hammarlund set, they could be sold as
desperately needed replacement spares for the old sets too.



Ah, just WHO is going to clone anything from the past and make any
money?

use a seeing eye tube mounted in a hole in the dial as opposed to a
meter movement, again, getting a run of new tubes made is possible if
you are buying several thousand. There are some surplus that could be
used if really needed too.


Your dreamin again. Its totally stupid to expect anyone might sell
thousands of NEW made copies of 1960 SW radios sets without conducting
a thorough market feasibility study. The COMPETION for what you
propose now has become so overwhelming that nobody in their right mind
would consider having say 10,000 new 6BA6, 6BE6 etc manufactured for a
production run of thousands of SW sets.

Before asking us silly questions, have you :-
1. Learnt all about SW tube radio, 2. Drawn up a probable, or
provisional parts list, 3. spent weeks chasing quotes for parts
exactly as yo specifiy, 4, Generally put in a whole lot of work so far
without relying on any of us, who, IMHO, will conclude you are on a
goose chase.

*I would use a separate power supply and speaker for several reasons.


Well of course, but you'll die when you work out the cost of
production for your project is 100 times what people now pay for SW
reception with a whole pile of features you'll probably not want to
include.

*I would have the radio take in B+ and heater voltage and put out 600
ohm +4 audio. A regular supply could be used at home or car battery
and a switchmode brick for B+. A headphone jack would be supplied off
this tube.

*The set should cover 500 kHz to 30 MHz, AM, SSB and CW, with a
product detector of course. A 455 kHz IF is needed so as to use common
mechanical or crystal filters, which are optional. There should also
be a 455 kHz IF out for an external synchronous detector.


All those features have already been well sorted out by old makers.

But there was a magazine called Electronics Australia which has now
been swallowed up by 'Silicon Chip' but they have a CD with the old
magazines monthly output from 1939 to 1965.
http://shop.siliconchip.com.au/radio...ch-1965-1.html

Perhaps within that magazine you'll find full articles about building
good SW radios with tubes which were second to none.

Hardly any of the parts used are now available, but hey, yo issa
dreamer, and you'll just dream them all up.
Reality is that you might spend years building such a set, at a
glacial rate of 1 tube stage per 3 months. My bet is that of the maybe
200 blokes who attempted to build the radios which are so well
described in the magazine, maybe 10 finished a set to a respectable
standard. Magazines became viable, because dreamers bought them.
Mostly do-little nerds as I recall. What's so rivettingly interesting
about SW reception? What form of media entertainament is worth
listening to on SW? What is available on SW which ain't available
elsewhere, apart from a pile of noise, poor audio, whistles, fade
outs, and old amateur blokes droning on and on about their latest
hospital operations? New York police maybe?

I regularly restore old radios. Last job was a 1947 Healing floor
standing 5 band AM radio for the fashionable Bling-Blang generation of
1947, ie, my parents generation. It has a 6J8 mixer plus 6U7 IF, and
is chockoblock with coils and special wafer switches but it does give
remarkably good reception of Radio America of China Calling even in
daytime, with a long wire antenna taken out to a nearby tree. Anyway,
I put in about 130 hours fixin up the old banger, and the one section
I didn't alter at all was the 3 band SW section. Not much alignment
was needed to maximise performance. Local MW was changed to ferrite
rod antenna replacing the horrible high impedance RF input tranny
which worked fine before the present which is riddled with hum
imposing itself on many incoming signals in the electro static portion
of the electromagnetic waves. The ferrite rod reacts to the magnetic
part of the incoming wave which is not affected by compact fluorescent
lamps et all.

But now we have local Digital Radio Broadcasting now all based on
frequencies up around 250Mhz. The local Australian Broadcasting
Commission, or ABC, has just begun trials here for broadcasting of all
they have on MW, 2 stations, and all they have on FM, another 2
stations, on digital. Don't ask me how DAB works. I can't find any
schematics of concise explanations.

So, listeners who have loved their old tubed radio set because it
carried the MW local stations now don't need to use their tubed set,
and can access the old AM station program noise free and with full
audio BW with hi-fi specs from their tiny little box sets for DAB.

Now sometimes ppl with radios capable of SW might try surfing the
bands, but now DAB is here ppl won't be able to surf these SW bands,
but then who ever did ?

There were 101 different ideas put forward for providing a decent
tubed SW radio which never saw commercial development and production,
such as the early synchrodyne. The superhet was deemed to be the best.
Racal had 3 mixers, and was remarkably stable for an old banger but
now with digtally generated oscillator F and all that chipery stuff
and computer controlled stuff, stablity is far better now. Wanna copy
a Yeasu?

If I wanted to build a 6 band SW radio now I think I might have 6 j-
fet RF amp stages well controlled by AVC, then 6 j-fets for
oscillators, and thus not need a special made bandswitch, except some
generic easy to buy wafer switch from Farnells with 6 positions. Mixer
could be one of many options, maybe more than one, to minimise
switching of the IF output. With such cheap small devices with high gm
and low noise, the cost is far less than a complex switch and just two
tubes to work on all bands. But all this is so easy to say, and such
things are easier said than done, and succes relies on YOU. And there
are very few ppl here who are heavily into farnarkling with HF radios,
so there are not many brains here to be picked, or if you do try,
you'll probably get 101 suggestions all requiring maybe years to
perfect and after that you still can't equal the best old sets.
I heard about a bloke who built a CD player using just generic opamps.
It took so long......

Any other comments?


But good luck with you quest. You'll definately need +60dB of that.

Patrick Turner.