[D. Peter Maus]

On 11/27/11 10:45 , D. Peter Maus wrote:
On 11/27/11 10:18 , NT wrote:
On Nov 27, 4:08 pm, wrote:
On Nov 26, 5:54 am, wrote:



On Nov 25, 6:44 pm, wrote:

On Nov 11, 5:52 am, 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.

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

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. I
would
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.

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

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.

Any other comments?

The need for testgear to align the IF will wipe out 99.9% of any
potential market.

As pointed out, its going to be far too expensive. If you took
that to
heart and tried to make something far cheaper, regeneration,
although
a definite compromise, is a dead sure way to cut costs a lot,
and has
angelic AGC performance. I recall a simple 3 valve 1930s regen set
giving rock steady audio on a signal even an exceptionally complex
modern dx set couldnt stabilise.

NT

One of the very reasons I DON"T like regens and direct
conversions is
"No Alignment".

You need to have some kind of sig gen and preferably a scope.
That's
a feature, not a bug.

Any hamfest in the US will net a working scope for a twenty dollar
bill and probably a usable RF generator for a similar sum. The
guitar
amp ****s will part them out for the tubes and throw them in the
dumpster often as not.

In a pinch a grid dipper and a solid state RF probe attached to
a DMM
will work.

If I were designing such a product, I'd do everything in my power to
avoid end user alignment with testgear, for one very simple
reason: it
wipes out 99.9% of your potential customers, its business suicide.

Perhaps one could use resonators instead of LCs, if you dont like
the
interstation garbage of agced reaction.

NT

Of course a valve radio is business suicide to begin with,
performance
per dollar has come a long way since the valve era. Number of valve
radios currently on the market is zero, so no-one has managed to make
them compete with 30cent ICs and 2cent transistors.


NT


Valves have a place in audio, for the truly faithful. But then,
audio only requires a few valve types, frequencies are easily
managed, and circuitry remains stable for much longer periods of
use. Whereas radio applications require more sophisticated valve
construction, and significantly different valve types for given
applications, to accomodate frequencies that stretch from 10X to
100000X audio frequencies.

What's comforting in radio with valve technology, is the general
sense that the technology itself is accessible. And widely
understood to be more forgiving. That valves may be removed, tested,
and replaced by the techologically limited, and operated under
conditions that would destroy solid state. Whereas, SS receivers,
self service requires a much higher level of skill, with a much
lower threshold of abuse. For those with limited technological
experience, this can be daunting. Especially, as in the case of this
receiver, during an emergency, where supply lines are uncertain, and
technical support is nonexistent.

I can see where the OP is coming from. Build an accessible receiver
that's fairly forgiving to extremes in noise, signal levels,
voltage, and hostile events, and you'd have a generally useful rig
for the general population in an emergency. It's a nice thought.

But as has been pointed out here multiple times, SS technology in a
proper design has proven more resistant to EMP than generally
believed, operating voltages are easier to generate, and manage,
power requirements are lower, and performace of the technology is
dramatically improved since the days of valve receivers. All at a
fraction of the cost. And in an emergency, valve supplies will be
just as short as SS components.

All of which points to the fact that a well designed kit radio for
use in emergencies would be more like the Ten-Tec 1254, than it
would be like a Hallicrafters S-40. And the Ten-Tec 1254 is a kit,
costs $200, and requires no user alignment, but offers significant
performance across the spectrum from LF through HF.

In a package that's available now.


From Ten-Tec:

"Model 1254 combines the satisfaction of the kit building experience
with the performance features expected in a modern HF receiver.
Building one’s own receiver from a kit has launched countless
thousands of people into communications careers or the hobbies of
amateur radio and shortwave listening (“SWLing”). You will build a
true dual-conversion superhet with a microprocessor-controlled
frequency synthesizer. Digital LED readout. Alignment is easy and
does not require complicated equipment. You only need a volt-ohm
meter and your ear; the kit provides its own 45 MHz test signal."


So there is some user alignment. But nothing that can't be
accomplished with what's in the kit, and by following instructions.

It doesn't get any simpler than this.

Ten-Tec has a video channel on YouTube, where you can see the
kit, watch it being constructed, adjusted and operated.

I've thought about putting one up at the cabin. But I've already
got an HF-150, there, sitting next to an S-53, and an RF-3100.