The "Two Transistor challenge" - taking things a bit too far?
 

"Michael Black" wrote in message
news:alpine.LNX.2.02.1402190105000.16359@darkstar. example.org...
On Wed, 19 Feb 2014, Phi wrote:

I still have the HP-35 and an HP-25 that can be programmed up to 49
steps.

What happens when you turn off the HP-25? Is it one that keeps the memory
alive, or do you lose everything after you typed it all in?

Michael


With mine, memory is lost when turned off.

The "Two Transistor challenge" - taking things a bit too far?
 

On 19/02/2014 09:32, gareth wrote:
"AndyW" wrote in message
...

(but then I enjoy retro-tech like making Baird televisors)


Mirror-drum, or Nipkow disk?

Nipow disk. I built my first one while at school using plans in Hobby
Electronics using my sister's 'The Partridge Family Album' LP, I thought
that it was the best use that it could be put to; she disagreed.

One of my later ones used a 'conveyer belt' instead of a disk which
produces a square screen.

LED or nitro-benzine as the polariser?

Polariser?
I used a neon as my light source, I didn't have any polarisation.
My later ones use LEDs at light sources and produce a much better
quality of image.

Andy

The "Two Transistor challenge" - taking things a bit too far?
 

On 19/02/2014 16:30, Michael Black wrote:
On Wed, 19 Feb 2014, AndyW wrote:

On 18/02/2014 10:58, 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 is something challenging about restricting your resources.
My most memorable receiver I ever built was made from a toilet roll
tube, wire, a crystal earpiece, tinfoil and paper hand-rolled
capacitor and some galena crystal as a detector.
I think I got more satisfaction out of that that I ever did from a
digitally programmable oscillator based beast.

I think that's something that may be lost.

People lament that in this day and age, it's difficult to attract the
young to the hobby, because how can it compete with the Internet?

Because I am a bit of a geek I get asked to run Jamboree on the Internet
for my local scout group in October (been doing it for about 10 years now).
When we have computers set up for text chat, chat rooms, voip, skype
video chat and multi participant video conferencing the kids are simply
not interested in talking on the radio. They can get crystal clear
communication and don't really care about some faint HF chat.

It is sad but to compete radio has to offer something new or different.
I would like to get them to build simple qrp sets and use WSPR to see
how far they can reach and also see how far they can communicate on qrp
with morse (albeit with some help).
They simply cannot make an internet capable computer and OS but they can
make a QRP set like a pixie on a breadboard in an hour and be picked up
around the world on WSPR.
Catch that buzz and then it is a short step to (very slow) morse
communication and hopefully getting them hooked.

And you don't compete with it, you show off things that are unique.

A simple project for a beginner is identical to what it was forty or
fifty years ago, a first project and when it actually gets working, what
an accomplishment. It's not because the simple project is comparable
with the electronic wonders of the 21st century, it's that you built it
and it worked.

I was asked to run a technology based badge for some scouts and had them
making crystal radios, some of them swore blind that it could not work
because there were no batteries despite building it themselves and hand
winding the coils.
The reaction by many is pure amazement that a bundle of wire and junk
can receive a radio station, it remind me of the buzz I first got as a
kid making a crystal set from plans in the eagle annual (I'm not old
enough to get one from new, I bought it in a jumble sale in the 70s)

The buzz is still there if you get them young enough and pre internet chat.

Andy

The "Two Transistor challenge" - taking things a bit too far?
 

"AndyW" wrote in message
...
On 19/02/2014 09:32, gareth wrote:

LED or nitro-benzine as the polariser?
Polariser?

To my eternal regret, because I disposed of them 38 years ago, I had a
pile of "Amateur Wireless" from the 1930s within which were designs
for mirror-drum scanners, and the modulation was not by a neon light
but with a constant light source which was then modulated by a series
of polarising filters, with one being variable to rotate the polarisation.

ISTR (38 years ago!!!) that the liquid used was nitro-benzene

The "Two Transistor challenge" - taking things a bit too far?
 

On 20/02/2014 11:51, gareth wrote:
"AndyW" wrote in message
...
On 19/02/2014 09:32, gareth wrote:

LED or nitro-benzine as the polariser?
Polariser?

To my eternal regret, because I disposed of them 38 years ago, I had a
pile of "Amateur Wireless" from the 1930s within which were designs
for mirror-drum scanners, and the modulation was not by a neon light
but with a constant light source which was then modulated by a series
of polarising filters, with one being variable to rotate the polarisation.

ISTR (38 years ago!!!) that the liquid used was nitro-benzene

OK I follow you now. I had a quick google and found out about
nitrobenzene and modulating polarisation. Never heard of it before. Live
and learn.

My original set up was as simple and agricultural as they come, vinyl
LP, scrap motor from a cassette player, Neon attached to am amplifier
behind the 'screen' and a camera made from a lens and an LDR recording
onto a cassette player - the bandwidth was low enough to record on audio.

My latest televisor was made from a circle of black plastic spinning on
a hand fan with a very small torch behind it modulated by the sound from
a small mp3 player. It all folds up and fits in a pocket.

Andy

The "Two Transistor challenge" - taking things a bit too far?
 

"AndyW" wrote in message
...
On 20/02/2014 11:51, gareth wrote:
"AndyW" wrote in message
...
On 19/02/2014 09:32, gareth wrote:
LED or nitro-benzine as the polariser?
Polariser?
To my eternal regret, because I disposed of them 38 years ago, I had a
pile of "Amateur Wireless" from the 1930s within which were designs
for mirror-drum scanners, and the modulation was not by a neon light
but with a constant light source which was then modulated by a series
of polarising filters, with one being variable to rotate the
polarisation.
ISTR (38 years ago!!!) that the liquid used was nitro-benzene
OK I follow you now. I had a quick google and found out about nitrobenzene
and modulating polarisation. Never heard of it before. Live and learn.
My original set up was as simple and agricultural as they come, vinyl LP,
scrap motor from a cassette player, Neon attached to am amplifier behind
the 'screen' and a camera made from a lens and an LDR recording onto a
cassette player - the bandwidth was low enough to record on audio.
My latest televisor was made from a circle of black plastic spinning on a
hand fan with a very small torch behind it modulated by the sound from a
small mp3 player. It all folds up and fits in a pocket.


Wow! How many lines and frames / sec?

The "Two Transistor challenge" - taking things a bit too far?
 

"gareth" wrote in message
...

Wow! How many lines and frames / sec?


A quick google yielded ...

http://www.tvhistory.tv/1935%20TV%20...20Part%202.htm


.... and look for "Kerr Cell"

The "Two Transistor challenge" - taking things a bit too far?
 

On 19/02/2014 18:51, Jerry Stuckle wrote:
On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote:
On 19/02/14 03:09, Jerry Stuckle wrote:
On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote:
"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.

Yup, same here. Except when you jig the chassis up for testing, the
anode lead is basically hanging in the air. Also, the CRT makes a great
capacitor - if you don't discharge it enough times before disconnecting
the anode lead, it can still set you back on your backside :)

If you discharged it by simply shorting the anode to chassis you could
damage the CRT.


I've heard that, but it never happened to me or anyone I know. But I
also agree that doesn't mean it can't happen.

Dead shorts to ground tend to smoke things.


--
J

The "Two Transistor challenge" - taking things a bit too far?
 

On 2/20/2014 4:15 PM, Brown Sugar wrote:
On 19/02/2014 18:51, Jerry Stuckle wrote:
On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote:
On 19/02/14 03:09, Jerry Stuckle wrote:
On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote:
"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.

Yup, same here. Except when you jig the chassis up for testing, the
anode lead is basically hanging in the air. Also, the CRT makes a
great
capacitor - if you don't discharge it enough times before disconnecting
the anode lead, it can still set you back on your backside :)

If you discharged it by simply shorting the anode to chassis you could
damage the CRT.


I've heard that, but it never happened to me or anyone I know. But I
also agree that doesn't mean it can't happen.

Dead shorts to ground tend to smoke things.



Not necessarily with static charges - which is what's on the CRT with
the HV removed.

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

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

The "Two Transistor challenge" - taking things a bit too far?
 

"Jerry Stuckle" wrote in message
...
On 2/20/2014 4:15 PM, Brown Sugar wrote:
On 19/02/2014 18:51, Jerry Stuckle wrote:
On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote:
On 19/02/14 03:09, Jerry Stuckle wrote:
On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote:
"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.

Yup, same here. Except when you jig the chassis up for testing, the
anode lead is basically hanging in the air. Also, the CRT makes a
great
capacitor - if you don't discharge it enough times before
disconnecting
the anode lead, it can still set you back on your backside :)

If you discharged it by simply shorting the anode to chassis you could
damage the CRT.

I've heard that, but it never happened to me or anyone I know. But I
also agree that doesn't mean it can't happen.

Dead shorts to ground tend to smoke things.

Not necessarily with static charges - which is what's on the CRT with the
HV removed.

Lightning is a static discharge, are you saying that doesn't smoke things?
--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk