On Tue, 18 Feb 2014, gareth wrote:

There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost nearly
a week's wages for the average working man, and so it was good economical
sense to try and use it as many ways as possible simultaneously.

Times have changes, and active devices with performance into the tens
of MegaHertz are now ten-a-penny, so what is achieved by competitions
such as the "Two Transistor Challenge" where it is the costs of switching
(manual, relays) which would be the major outlay?

Not carping, just curious.

There have always been "contests" like that, though sometimes they were
about "build a whole receiver using the same transistor type", or "build a
receiver without any ICs" after ICs had come around.

SOme of the time it's not about design, but the building, so one can just
copy what existed.

In some cases, this is just about getting people to build something, so a
two transistor whatever is simple and might attract more people.

But in suggesting a problem, people may come up with interesting
solutions. I remember a bit years ago where a bipolar transistor was used
to generate two different crystal controlled frequencies, the frequency
chosen by how polarity was applied. I forget the details, but it relied
ont he transistor having some amplification in an unexpected area.

If people don't have to be frugal, then such things never get found.

Or think about in the thirties. People had little money, so yes, a simple
transceiver would be a great thing. Someone decided to build that, in
effect a tube that was a superrenerative receiver and on transmit a
modulated oscillator. It helped get people on 10metres (I think) and
56MHz, and 112MHz and so on. It would generate activity on an otherwise
unused band because it was cheap and simple, so people built them. The
cost of the switch was less than the cost of the tubes. And every so
often, such a thing would be banned, as rules for more stability came into
effect, and usually by then that band was populated. So the concept moved
to a higher frequency, until it was deemed to unstable for there too, and
up to the next band. They even existed in the 420MHz band, and while
generally nobody built them, at 1296MHz people often got a start with
APX/6 surplus that amounted to simple equipment. 20 to 30 years ago,
23,000MHz got a boost with surplus door openers. SImple equipment gets
more people onto a band than complicated equipment, and some will move on
to fancier equipment.

That same sort of thing, an active element switched between a superregen
receiver and a modulated oscillator still existed till at least 30 years
ago, in license free walkie talkies, first in the 27MHz range and then in
the 49MHz range. Even then the cost of the switch was seen as simpler than
more transistors.

It can also teach something. You can reuse the transistor for two
functions, by switching the three leads of the transistor, which means
much more complication. But if people see that, they may learn that
design can become simpler by more complication. More transistors seem to
complicate things, but if it does away with switching, it may simplify the
design overall.

Michael

"Michael Black" wrote in message
news:alpine.LNX.2.02.1402181359580.14557@darkstar. example.org...
On Tue, 18 Feb 2014, gareth wrote:
There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost nearly
a week's wages for the average working man, and so it was good economical
sense to try and use it as many ways as possible simultaneously.
Times have changes, and active devices with performance into the tens
of MegaHertz are now ten-a-penny, so what is achieved by competitions
such as the "Two Transistor Challenge" where it is the costs of switching
(manual, relays) which would be the major outlay?
Not carping, just curious.

There have always been "contests" like that, though sometimes they were
about "build a whole receiver using the same transistor type", or "build a
receiver without any ICs" after ICs had come around.

What I find intriguing is the realisation that valves ("tubes" to you?) can
be operated with only 12V on the anode.

On 2/18/2014 3:00 PM, gareth wrote:
"Michael Black" wrote in message
news:alpine.LNX.2.02.1402181359580.14557@darkstar. example.org...
On Tue, 18 Feb 2014, gareth wrote:
There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost nearly
a week's wages for the average working man, and so it was good economical
sense to try and use it as many ways as possible simultaneously.
Times have changes, and active devices with performance into the tens
of MegaHertz are now ten-a-penny, so what is achieved by competitions
such as the "Two Transistor Challenge" where it is the costs of switching
(manual, relays) which would be the major outlay?
Not carping, just curious.

There have always been "contests" like that, though sometimes they were
about "build a whole receiver using the same transistor type", or "build a
receiver without any ICs" after ICs had come around.

What I find intriguing is the realisation that valves ("tubes" to you?) can
be operated with only 12V on the anode.



I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode

I haven't done anything with radar in well over 30 years, so I don't
know if they still do it or not. But I wouldn't be surprised. At first
glance it sounds crazy - but it made for a very simple and efficient way
to couple the output of the magnetron to the waveguide.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

"Jerry Stuckle" wrote in message
...

I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode


As in, "Flying by aeroplanes is perfectly safe, it's only when you crash
that it becomes dangerous"? :-)

On 18/02/14 20:31, Jerry Stuckle wrote:

There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost
nearly
a week's wages for the average working man, and so it was good
economical
sense to try and use it as many ways as possible simultaneously.
Times have changes, and active devices with performance into the tens
of MegaHertz are now ten-a-penny, so what is achieved by competitions
such as the "Two Transistor Challenge" where it is the costs of
switching
(manual, relays) which would be the major outlay?
Not carping, just curious.

There have always been "contests" like that, though sometimes they were
about "build a whole receiver using the same transistor type", or
"build a
receiver without any ICs" after ICs had come around.

What I find intriguing is the realisation that valves ("tubes" to
you?) can
be operated with only 12V on the anode.

No unusual at all.

Not only were a number of valves for the car radio (and possibly other)
markets available, I recall designs which use 'ordinary' valves with
6.3V AC heaters and a voltage doubler and rectifier to provide the "HT".
I recall a one valve design in Radio Constructor, which I build. It was
the 'cover article'. The design called for an Eddystone Box, far too
expensive, so I used a tin box from some short bread.


I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode

I haven't done anything with radar in well over 30 years, so I don't
know if they still do it or not. But I wouldn't be surprised. At first
glance it sounds crazy - but it made for a very simple and efficient way
to couple the output of the magnetron to the waveguide.


No reason why it shouldn't be done. I can imagine some of the more
"technically challenged" struggling with it but there are always those
who insist that all who have been designing kit for years have got it
wrong.

In article , Brian Reay
wrote:

On 18/02/14 20:31, Jerry Stuckle wrote:

There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost
nearly
a week's wages for the average working man, and so it was good
economical
sense to try and use it as many ways as possible simultaneously.
Times have changes, and active devices with performance into the tens
of MegaHertz are now ten-a-penny, so what is achieved by competitions
such as the "Two Transistor Challenge" where it is the costs of
switching
(manual, relays) which would be the major outlay?
Not carping, just curious.

There have always been "contests" like that, though sometimes they were
about "build a whole receiver using the same transistor type", or
"build a
receiver without any ICs" after ICs had come around.

What I find intriguing is the realisation that valves ("tubes" to
you?) can
be operated with only 12V on the anode.

No unusual at all.

Not only were a number of valves for the car radio (and possibly other)
markets available, I recall designs which use 'ordinary' valves with
6.3V AC heaters and a voltage doubler and rectifier to provide the "HT".
I recall a one valve design in Radio Constructor, which I build. It was
the 'cover article'. The design called for an Eddystone Box, far too
expensive, so I used a tin box from some short bread.


I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode

I haven't done anything with radar in well over 30 years, so I don't
know if they still do it or not. But I wouldn't be surprised. At first
glance it sounds crazy - but it made for a very simple and efficient way
to couple the output of the magnetron to the waveguide.


No reason why it shouldn't be done. I can imagine some of the more
"technically challenged" struggling with it but there are always those
who insist that all who have been designing kit for years have got it
wrong.

Indeed it is rather similar to what was done with TV and monitor CRTs,
to interface the screen with people's living rooms at an appropriate
potential!

--

Percy Picacity

On 2/18/2014 4:29 PM, Percy Picacity wrote:
In article , Brian Reay
wrote:

On 18/02/14 20:31, Jerry Stuckle wrote:

There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost
nearly
a week's wages for the average working man, and so it was good
economical
sense to try and use it as many ways as possible simultaneously.
Times have changes, and active devices with performance into the tens
of MegaHertz are now ten-a-penny, so what is achieved by competitions
such as the "Two Transistor Challenge" where it is the costs of
switching
(manual, relays) which would be the major outlay?
Not carping, just curious.

There have always been "contests" like that, though sometimes they were
about "build a whole receiver using the same transistor type", or
"build a
receiver without any ICs" after ICs had come around.

What I find intriguing is the realisation that valves ("tubes" to
you?) can
be operated with only 12V on the anode.

No unusual at all.

Not only were a number of valves for the car radio (and possibly other)
markets available, I recall designs which use 'ordinary' valves with
6.3V AC heaters and a voltage doubler and rectifier to provide the "HT".
I recall a one valve design in Radio Constructor, which I build. It was
the 'cover article'. The design called for an Eddystone Box, far too
expensive, so I used a tin box from some short bread.


I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode

I haven't done anything with radar in well over 30 years, so I don't
know if they still do it or not. But I wouldn't be surprised. At first
glance it sounds crazy - but it made for a very simple and efficient way
to couple the output of the magnetron to the waveguide.


No reason why it shouldn't be done. I can imagine some of the more
"technically challenged" struggling with it but there are always those
who insist that all who have been designing kit for years have got it
wrong.

Indeed it is rather similar to what was done with TV and monitor CRTs,
to interface the screen with people's living rooms at an appropriate
potential!


Hmmm, they must have done it differently over there. I've been bitten a
number of times by not being careful around the anode lead on a CRT.
The cathode is nearer ground potential because it's exposed on the back
of the tube.

You'd think being bitten by 25KV the first time would teach me a lesson.
But some people never learn

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

"Jerry Stuckle" wrote in message
...
On 2/18/2014 4:29 PM, Percy Picacity wrote:
In article , Brian Reay wrote:
On 18/02/14 20:31, Jerry Stuckle wrote:
There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost
nearly
a week's wages for the average working man, and so it was good
economical
sense to try and use it as many ways as possible simultaneously.
Times have changes, and active devices with performance into the
tens
of MegaHertz are now ten-a-penny, so what is achieved by
competitions
such as the "Two Transistor Challenge" where it is the costs of
switching (manual, relays) which would be the major outlay?
Not carping, just curious.

There have always been "contests" like that, though sometimes they
were
about "build a whole receiver using the same transistor type", or
"build a receiver without any ICs" after ICs had come around.

What I find intriguing is the realisation that valves ("tubes" to
you?) can be operated with only 12V on the anode.

No unusual at all.

Not only were a number of valves for the car radio (and possibly other)
markets available, I recall designs which use 'ordinary' valves with
6.3V AC heaters and a voltage doubler and rectifier to provide the "HT".
I recall a one valve design in Radio Constructor, which I build. It was
the 'cover article'. The design called for an Eddystone Box, far too
expensive, so I used a tin box from some short bread.

I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode

I haven't done anything with radar in well over 30 years, so I don't
know if they still do it or not. But I wouldn't be surprised. At
first
glance it sounds crazy - but it made for a very simple and efficient
way
to couple the output of the magnetron to the waveguide.

No reason why it shouldn't be done. I can imagine some of the more
"technically challenged" struggling with it but there are always those
who insist that all who have been designing kit for years have got it
wrong.

Indeed it is rather similar to what was done with TV and monitor CRTs,
to interface the screen with people's living rooms at an appropriate
potential!

Hmmm, they must have done it differently over there. I've been bitten a
number of times by not being careful around the anode lead on a CRT. The
cathode is nearer ground potential because it's exposed on the back of the
tube.

You'd think being bitten by 25KV the first time would teach me a lesson.
But some people never learn

I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal.
The viewer was protected by a thick layer of glass that also formed an
implosion guard. Colour CRTs had around 25kV on the anode, and in early
models with anode currents of 1mA or so the line output stage was lead
shielded to reduce X-radiation. Happy days.
--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk

On Tue, 18 Feb 2014 15:31:18 -0500, Jerry Stuckle wrote:

I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode

I haven't done anything with radar in well over 30 years, so I don't
know if they still do it or not. But I wouldn't be surprised. At first
glance it sounds crazy - but it made for a very simple and efficient way
to couple the output of the magnetron to the waveguide.

Microwave ovens still do that. At least, my Toshiba does.

--
Jim Mueller

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.

On 2/18/2014 6:02 PM, Jim Mueller wrote:
On Tue, 18 Feb 2014 15:31:18 -0500, Jerry Stuckle wrote:

I remember back in the 70's we had radar sets with ZERO volts on the
magnetron's anode (DC ground). Of course, there was -3KV or so on the
cathode

I haven't done anything with radar in well over 30 years, so I don't
know if they still do it or not. But I wouldn't be surprised. At first
glance it sounds crazy - but it made for a very simple and efficient way
to couple the output of the magnetron to the waveguide.

Microwave ovens still do that. At least, my Toshiba does.


Probably. Although I could kick myself. In the last 4 years I threw
away two microwaves - an 1100W one and a 1300W one (both had control
boards fail). It wasn't until later I thought about taking them apart
and using the power supply for a homebrew amplifier.

Not going to do that again!

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================