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

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

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

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

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.

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

If you only have 2 transistors then you have to make everything do
multiple duty; it pushes your technical ability. IME if you have
unrestricted resources then there is a tendency to think in functional
blocks and not an integrated system.

Good engineering is not achieved when you can add nothing more, it is
achieved when you can take away nothing else. You of all people should
appreciate that.

Andy

On 18/02/2014 15:21, Phi wrote:
I paid about £180 for an HP35 in 1973, this calculator used reverse
polish notation (no equals key).

HP15C was my best calculator (still use it) its quality is such that it
still sells for £150+ on ebay.
Complex maths, matrix manipulation, polar to rectangular conversion all
in a 1981 calculator. Lovely bit of engineering.

Andy

"AndyW" wrote in message
...

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


Mirror-drum, or Nipkow disk?

LED or nitro-benzine as the polariser?

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?

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.

Michael

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


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.

Absolutely true. One of my foundation types constructed a simple bit of
circuitry to comply with the course.
He rang me afterwards in a state of excitement - "It works - it bloody
works!" he exclaimed.

Les.

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.

--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk
..
Ubuntu 12.04
Thunderbirds are go.

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.

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

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