In article ,
says...

In message , Arny Krueger
writes

"Terry Casey" wrote in message
...


A couple of questions regarding that list:

Why is the HRC channel spacing offset[1] by 300Hz - 6.0003MHz instead of
6MHz?

I don't know.

I recall once specially tweaking a UK 8MHz HRC harmonic comb generator
(to which all of the TV channels were locked). It was a little above (or
was it below?) 8MHz. There was a reason for this, but at the moment, I
can't remember what it was.


One system where this was done was the old BT Westminster system -
probably very useful in an area where I would expect a lot of off-air
reception problems.

I don't know what offset they used but, as an example, if you alter the
comb to 7.990963855MHz, channel E45 is bang on (663.25MHz) so, if you
centred the five off-airs around this using E41, E43, E45, E47 and E49,
the worst case error will be +/-36kHz from the nominal frequency.

--

Terry

In article ,
says...

David Looser wrote:

"Michael A. Terrell" wrote in message
m...

"Geoffrey S. Mendelson" wrote:

hwh wrote:
On 2/5/12 7:04 PM, J. P. Gilliver (John) wrote:
But you've got to remember that this is the country that kept 405-line
going for, I think, longer after 625 started than it had been going
before that.

Erm, 405 started before the war and was alone until 1964? Then it
continued for another 20 years?

Someone said the last two years of 405 line signals were generated by an
unusal
method, I think the word they used was "endearing". What was it?

BTW, the BBC shut down TV broadcasts in for World War II, and resumed
them at the exact point in the same broadcast after the war. :-)


That's very easy to do with film. I should know. I loaded and ran
truckloads of 16 mm film on a pair of RCA TP66 projectors in the '70s.

I'm sure it is, but as we've already established that the "exact point in
the same broadcast" bit isn't true its not relevant.

The myth that the engineers simply ceased transmission half-way through a
programme and left the station like a sort of Mary Celeste has been
widespread, but it is a myth. In fact there was an orderly shut down and the
film in the machines would have been rewound and put into storage before the
staff left. It would have been 35mm film (the BBC didn't have facilities for
transmitting from 16mm film pre-war) and thus on nitrate stock. NOT putting
it into proper storage would have constituted a fire hazard and been in
contravention of fire regulations.


It still would have been no problem to load and start it at exactly
the same frame, if they had wanted to.

All hypothetical. As David said earlier, it is a myth that transmission
was cut in the middle of the cartoon. Station logs exist that say
different.

Another myth is that the Television Service resumed in 1946 with the
same cartoon. It didn't!

The cartoon WAS repeated that day - but it wasn't the first programme.

--

Terry

In article ,
Michael A. Terrell wrote:

They were a dollar. This isn't the same as what I saw, but it will
give you some idea:
http://i00.i.aliimg.com/photo/v0/255041326/DZ_909A_6_way_power_outlet_with.jpg
since the meter was next to the power switch and cord.

That's what we'd call a trailing socket. To be used with an extension
lead. I thought you meant permanently installed sockets. But perhaps you
can't tell the difference.

It look like it would also accept other than the UK 13 amp plug - which is
why some tourists might buy it. It doesn't conform to UK regs.

--
*Experience is something you don't get until just after you need it *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Mortimer wrote:
Don't/didn't TV studios have some form of backup generators in case of
power failure? At least enough to power VTs and sufficient lighting for
news reports etc, even if not enough to light whole studios?

TV centre had IIRC two feeds from different parts of the grid or whatever
and both failed.

I suppose for a first night launch, they'd probably planned live events
that would have taken a lot of power for lighting.

It would have needed a massive generator to fully run TVC. It did have a
small standby one which could manage a continuity announcer.

Think the maximum load at TVC was 11Mw. But Charles will likely remember
better.

--
*To err is human. To forgive is against company policy.

Dave Plowman London SW
To e-mail, change noise into sound.

Michael A. Terrell wrote:

Sigh. America was supplying AKA: LENDING planes and other war
materials to help Europe clean up their mess, long before Japan attacked
Pearl Harbor. Is the school system really that bad where you grew up?

Don't forget that the schools in the UK have many teachers who are
socialist and deny the true
history of the 20th century.

You must remember that a lot
of people in the UK are socialists, and they hate the US because that
country has demonstrated
that capitalism works.

There's also a lot of envy in the UK for the US, amongst those who are
given to envy. And that of course is the socialists.

Bill

Michael A. Terrell wrote:


Do you know that the channel combiners in a CATV head end
were wired in odd and even banks, on separate groups to prevent IMD
caused in the passive mixing?

Even now if we use passive filters to combine channels we try to arrange
the filters as follows (for example)
Filter 1: 21, 25, 29, 33 etc
Filter 2: 22, 26, 30, 34 etc
Filter 3: 23, 27, 31, 35 etc
Filter 4: 24, 28, 32, 36 etc
The filter outputs are combined using passive combiners. The idea is to
prevent interactivity between adjacent channel filters.

Bill

David Looser wrote:

But now I realise that you are talking about plug-in extention sockets, and
I notice from the photo that that one has "universal" sockets that will
accept US and a variety of European plugs as well as UK ones. Personally I
wouldn't touch one of those with a barge-pole.

You can get plastic barge poles nowadays.

Bill

Don Pearce wrote:

On Thu, 09 Feb 2012 16:30:25 -0500, "Michael A. Terrell"
wrote:


David Looser wrote:

"Michael A. Terrell" wrote in message
...

J G Miller wrote:

All because of the perceived need to produce weapons of mutual
annihilation.


We wouldn't need to do it, if you Europeans would stop starting World
Wars.


According to the history books the US entered WW2 because it was attacked by
the Japanese. It seems that Michael A. Terrell thinks that Japan is in
Europe.


Sigh. America was supplying AKA: LENDING planes and other war
materials to help Europe clean up their mess, long before Japan attacked
Pearl Harbor. Is the school system really that bad where you grew up?

I hope you are not imagining that America did that from anything other
than good, solid self-interst.


Sigh. No, they did it because they know that you Europeans never
could play together without starting stupid fight. What better reason
did we have to stop the production of civilian goods in the US and build
weapons for you losers to kill each other?


--
You can't have a sense of humor, if you have no sense.

David Looser wrote:

"Michael A. Terrell" wrote in message
...


They were a dollar. This isn't the same as what I saw, but it will
give you some idea:
http://i00.i.aliimg.com/photo/v0/255041326/DZ_909A_6_way_power_outlet_with.jpg
since the meter was next to the power switch and cord.

Right. You started all this by refering to European sockets which had to be
installed in equipment racks. So I naturally assumed that you were talking
about UK specific installation sockets being sold in flea markets in the US.

But now I realise that you are talking about plug-in extention sockets, and
I notice from the photo that that one has "universal" sockets that will
accept US and a variety of European plugs as well as UK ones. Personally I
wouldn't touch one of those with a barge-pole. Those sort of "universal"
sockets rarely make good contact whilst the meter is clearly for show, it
would tell you nothing useful. I'm sure it would not be legal to sell those
here as the sockets appear not to have shutters, which probably explains why
I've not seen one.


I wouldn't touch one, even if I needed the voltmeter.

--
You can't have a sense of humor, if you have no sense.

Ian Jackson wrote:

In message , Michael A.
Terrell writes



Do you know that the channel combiners in a CATV head end
were wired in odd and even banks, on separate groups to prevent IMD
caused in the passive mixing?

It might have depended on whose combiners you were using.

I hadn't heard about this so, one day (it must have been back in the
80s), I decided to do a quick test to see if it was true. To be honest,
I don't think I saw much difference whichever way I grouped the
channels. From what I remember, with the modulators putting each out
60dBmV, all the intermod products were at least 85dB down, and were
rather difficult to measure quickly. Such low levels of intermod would
have had a negligible impact on the overall system performance.


How many channels and at what signal levels did you try it on? We
had seven six port combiners in two groups of eight for a 36 channel
headend. The six outputs were combined in the seventh unit and
amplified before leaving the building. It did help in some
installations, where HSP were used for off air processing and for
stations who would push their character generators to over 100%
modulation from affecting other channels.


--
You can't have a sense of humor, if you have no sense.