On 24/02/2014 08:12, gareth wrote:

Picking up on your BW comment, AIUI, the Baird transmssions of 30 line
pictures
were also of the audio BW, and were transmitted as part of the normal
broadcast,
but not at the same time as the audio; it was either speech or video, but
not
simultaneously!

I read that.
You would think that it would be trivial to transmit on 2 channels; one
for the video and one for the sound.

The bloke who invented thermal socks should have thought of that.

Andy

"AndyW" wrote in message
...
On 24/02/2014 08:12, gareth wrote:
Picking up on your BW comment, AIUI, the Baird transmssions of 30 line
pictures
were also of the audio BW, and were transmitted as part of the normal
broadcast,
but not at the same time as the audio; it was either speech or video, but
not
simultaneously!

I read that.
You would think that it would be trivial to transmit on 2 channels; one
for the video and one for the sound.


Not at that time, when what most people could afford was a blooper,
although admittedly it was probably the rich who could afford Baird
Televisors
and therefore could have stretched to another set for a second channel.

On Tue, 25 Feb 2014, AndyW wrote:

On 24/02/2014 08:12, gareth wrote:

Picking up on your BW comment, AIUI, the Baird transmssions of 30 line
pictures
were also of the audio BW, and were transmitted as part of the normal
broadcast,
but not at the same time as the audio; it was either speech or video, but
not
simultaneously!

I read that.
You would think that it would be trivial to transmit on 2 channels; one for
the video and one for the sound.

But at the time, it would have been expensive, another receiver for the
second channel, two transmitters at the transmitting end. And wasn't it
the era of silent films, or at least silent films weren't that long in the
past? "Who needs the hear sound while watching a picture?"

Much later, some used ISB (independent sideband) to send SSTV and have
audio at the same time. Audio on one sideband, the SSTV signal on the
other. But that's even worse, two whole receivers and two whole
transmitters at both ends, all that selectivity and stability that
wouldn't have been available earlier.

Michael


The bloke who invented thermal socks should have thought of that.

Andy

"Michael Black" wrote in message
xample.org...
On Tue, 25 Feb 2014, AndyW wrote:
On 24/02/2014 08:12, gareth wrote:
Picking up on your BW comment, AIUI, the Baird transmssions of 30 line
pictures
were also of the audio BW, and were transmitted as part of the normal
broadcast,
but not at the same time as the audio; it was either speech or video,
but
not
simultaneously!
I read that.
You would think that it would be trivial to transmit on 2 channels; one
for the video and one for the sound.
But at the time, it would have been expensive, another receiver for the
second channel, two transmitters at the transmitting end. And wasn't it
the era of silent films, or at least silent films weren't that long in the
past? "Who needs the hear sound while watching a picture?"
Much later, some used ISB (independent sideband) to send SSTV and have
audio at the same time. Audio on one sideband, the SSTV signal on the
other. But that's even worse, two whole receivers and two whole
transmitters at both ends, all that selectivity and stability that
wouldn't have been available earlier.

TX could have been simpler had they combined audio and video using
quadrature modulation and a pilot tone, much as is / was used for the
colour subcarrier in PAL (also NTSC?) TV, but I doubt that anyone,
even the filthy rich (or even those who like to boast about how rich
they are :-) ), could have afforded the concomitant RX complexity
on their household budgets!

And talking of colour TV encoding, ISTR ...

NTSC - Never Twice the Same Colour

SECAM - System Essentially Contrary to the American Method

PAL - Peace At last!

BUT, didn't Logie Baird (not to be confused with Yogi Bear :-) )
do some experimentation with colour TV on the mechanical approach
anyway?

On 25/02/2014 16:00, gareth wrote:

BUT, didn't Logie Baird (not to be confused with Yogi Bear :-) )
do some experimentation with colour TV on the mechanical approach
anyway?

He did indeed produce colour TV, and the video recorder and, of course,
thermal socks.

Andy

"AndyW" wrote in message
...
On 25/02/2014 16:00, gareth wrote:

BUT, didn't Logie Baird (not to be confused with Yogi Bear :-) )
do some experimentation with colour TV on the mechanical approach
anyway?

He did indeed produce colour TV, and the video recorder and, of course,
thermal socks.

That Baird was living and working in a largely pre-techincal age, puts to
shame
all those grown-ups of today who exist with beginners' licences; especially
where those
licences are targetted at the 5-year-old.

On 2014-02-18, 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?


I remember my first home build radio: a earphone with just a 1N34 diode
in
parallel, an outdoor antenna and a good ground. Lots of listening hours of
a nearby AM 1230 KHz transmiter.

With a single FET regenerative receiver I could listen shorwave radios
from all over the world.

I like to work with very simple electronic equipment: I am reading and
replying to this news group with a 20 MHz 80286, 1 MBy memmory and all
programs in a 1.44
diskette (no Hard Drive).

Alejandro Lieber
LU1FCR
Rosario Argentina

--

SDF Public Access UNIX System - http://sdf.org

On 2/26/2014 11:09 AM, Alejandro Lieber wrote:
On 2014-02-18, 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?


I remember my first home build radio: a earphone with just a 1N34 diode
in
parallel, an outdoor antenna and a good ground. Lots of listening hours of
a nearby AM 1230 KHz transmiter.

With a single FET regenerative receiver I could listen shorwave radios
from all over the world.

I like to work with very simple electronic equipment: I am reading and
replying to this news group with a 20 MHz 80286, 1 MBy memmory and all
programs in a 1.44
diskette (no Hard Drive).

Alejandro Lieber
LU1FCR
Rosario Argentina


I can understand this. Back in Junior High (middle school nowadays), my
parents got me an electronics projects kit. It used a 1T4 for the
active element; a D cell provided filament voltage and a 45V battery
(looked like a long 9V battery) provided the plate voltage.

I built all kinds of things from the examples, including regen
receivers. I spent hundreds of hours with it - probably one of the best
money my parents spent to keep me out of trouble . It was advanced
enough to keep me occupied, yet simple enough that it taught me a lot
about how more advanced (at least to me, at the time) circuits work.

I still like the simple electronics. However, simple receivers like
that just won't work for me now. Something about the 5KW AM transmitter
in my back yard...

There is a lot to be said for simplicity!

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

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

"Alejandro Lieber" wrote in message
...
On 2014-02-18, 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?
I remember my first home build radio: a earphone with just a 1N34 diode
in
parallel, an outdoor antenna and a good ground. Lots of listening hours of
a nearby AM 1230 KHz transmiter.
With a single FET regenerative receiver I could listen shorwave radios
from all over the world.
I like to work with very simple electronic equipment: I am reading and
replying to this news group with a 20 MHz 80286, 1 MBy memmory and all
programs in a 1.44
diskette (no Hard Drive).

Well done, that man!

"Jerry Stuckle" wrote in message
...

I still like the simple electronics. However, simple receivers like that
just won't work for me now. Something about the 5KW AM transmitter in my
back yard...

The same for me 50 years ago. Home town was Portishead, and the TXs of
the international shipping Portiishead Radio were half a mile away across
the valley!