Mains filters
 

I guess you would get it on and off capacitively. Not too difficult to make
a cap of a few decimals of a uF at several hundred kV working, I would have
thought. You'd then use these to bridge any high inductances in the way,
such as tranny windings, and to get the data on and off. Depending on the
frequencies involved, you may actually get away with a few hundred pF.

Perhaps but I don't seem to remember seeing much else apart from longish
glass insulators big switch gear and fecking big trannies!...


I'm sure that such caps must have existed when megawatt main UHF TV
transmitter sites, such as Sandy Heath, used valve transmitters at the
bottom of the mast ( perhaps still do ?? ).

Klystons 'tho solid state may be used there now.

Do note that the megawatt etc is radiated power, much more to do with
aerial gains. They don't have megga-watt UHF TV tx'es....


--
Tony Sayer

Mains filters
 

In article ,
Don Pearce wrote:
You've never heard things like a fridge splat etc which is mains borne?
Of course it depends on the design of the power supply in your amp, etc.

I've got a dedicated radial circuit with its own earth feeding my AV
equipment.

No - never heard a thing come through the mains. If I started hearing
stuff now, I wouldn't be buying mains filters - I'd be fixing the
wiring.

Hmm. Switch off an inductive load like a motor on the same ring as an amp
and you'll hear it - or at least be able to measure the spike.

--
*A fool and his money are soon partying *

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

Mains filters
 

In article , Iain Churches
wrote:

Hello Glenn. A couple of days ago, I popped in for 30 secs to an audio
demo at a local dealership to take him some audition material. He was
demonstrating a mains filter unit. He had a tunable RF gadget with a
small inbuilt speaker which he plugged into a wall socket. Radio
transmissions and very loud hash could clearly be heard. Then he
plugged the gadget into one of the filtered outlets. Silence.

May be a very useful device if you happen to have such an RF
detector/demodulator/amp connected to the mains and you want to cut down
the noise it makes without bothering to unplug it. ;-

The unit was about 4U in height, and had ten mains outlets on the rear
panel.

I was there for only a few seconds, (car parked on a yellow line) The
dealer has promised me some literature.

The gain, etc, of the device used to produce audible noises from the
'mains' might help.. . :-)

AIUI though, most decent audio equipment isn't actually designed
specifically to demodulate and amplify mains interference. Perhaps he
avoided demoing with audio equipment as the main (pun) result might have
been to warn people not to buy that specific item of equipment. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

In article , Glenn
Richards wrote:


You can't hear much above 20kHz.

Varies from one person to another, but what you say is broadly correct so
far as we can tell.

But signals at frequencies above this will affect what you do hear,
harmonics, interaction etc.

What evidence do you have for the above? There have been some claims to
this effect, but tests I've seen don't show much support for the idea.

Why do you think there's been so much work done on DVD-A, SACD etc,
using sample rates of 96kHz or even 192kHz, rather than 44.1?

Various reasons. :-)

e.g. a concern (a la. Peter Craven) for avoiding unwanted *in band* time
dispersion effects. Moving the bandwidth up gives more elbow room for
ensuring a well-controlled response in band.

e.g. Making 24-bit-sample recordings makes it easier to avoid running out
of dynamic range by accident, but this may not matter to the final result.

e.g. Marketing and the need to replace (patents expired) audio CD with a
new format (with new patents) and get people to re-buy the same material
yet again. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

In article , Glenn Richards
wrote:


I would generally be of the opinion that if you've got a "normal" setup
at home (one PC, turned on when needed) filtering etc probably wouldn't
make a difference. But when you're sat next door to a scaled down
version of Telehouse you probably do want some filtering.

The primary test is to try listeing to your audio equipment with no source
playing. If you can hear background noise - or clicks/pops/etc - with the
'interfering' equipment working then a filter may be of use. If you can't,
then it seems unlikely to be of any use.

Hence there is no reason to wonder or speculate about this in a specific
case. Just test and decide.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

"tony sayer" wrote in message
...
I guess you would get it on and off capacitively. Not too difficult to
make
a cap of a few decimals of a uF at several hundred kV working, I would
have
thought. You'd then use these to bridge any high inductances in the way,
such as tranny windings, and to get the data on and off. Depending on the
frequencies involved, you may actually get away with a few hundred pF.

Perhaps but I don't seem to remember seeing much else apart from longish
glass insulators big switch gear and fecking big trannies!...


I'm sure that such caps must have existed when megawatt main UHF TV
transmitter sites, such as Sandy Heath, used valve transmitters at the
bottom of the mast ( perhaps still do ?? ).

Klystons 'tho solid state may be used there now.

Do note that the megawatt etc is radiated power, much more to do with
aerial gains. They don't have megga-watt UHF TV tx'es....


--
Tony Sayer


Yeah, know all about ERPs, but do the flat panel transmission antennas
actually have much gain ? Thought they were just a bunch of co-phased
dipoles. Bet the launch power from the tx is still a good 2 or 300 kW,
though, and I'd bet that there was a fair whack of volts on the klystron to
get there ...

Arfa

Mains filters
 

In article , Iain Churches
wrote:


It's a beautiful sunny day here. I am just off for a morning walk down
to the sea with the Airedale.

Didn't Warfedale make them? Why aren't you taking *both* speakers for a
walk?... :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

In article , Don Pearce
wrote:


I am a grumpy old man - that is what keeps me so happy. Today it is
trying to snow, and I am about to go for a walk down to Sainsbury's to
get some food.

I should also be 'grumpy' at this point. We had water coming through a
ceiling on Monday due to snow melt getting in via a flat roof. Currently
looking out at occasional showers of rain/snow/sleet and seeing if the
large tub behind one speaker is going to get any more contents...

Had some plastic sheeting tacked over the roof as a temporary measure this
morning, so keep yer fingers crossed that it helps!

Despite the above, at present I don't feel grumpy, but if we get more
floods I may decided to feel less cheery than usual...

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Mains filters
 

I
Yeah, know all about ERPs, but do the flat panel transmission antennas
actually have much gain ?

They stack and phase 'em to get the pattern/gain/and whatever
directivity they want..

Thought they were just a bunch of co-phased
dipoles.

Some are some aren't. Kathrin do some info on theirs...

Bet the launch power from the tx is still a good 2 or 300 kW,

Depends. Take the Heath, IIRC theres a 1000 K going to the North, but
not as much to the South on the analogue stack but the DTV is different
again..

seem to remember it was around 50 -70 K up the pipe..

though, and I'd bet that there was a fair whack of volts on the klystron to
get there ...

15 kV ish IIRC...

Arfa



--
Tony Sayer

Mains filters
 

In article , Arfa Daily
wrote:


To Tony. You're right. In recent years, the electricity companies have
installed fibre optic links, but I'm fairly sure that when they first
started using this method of communicating amongst themselves, they did
make use of the full distribution network, including the supergrid, but
I may be wrong on that. How much power volts are on the line, shouldn't
make any difference. It's still just a piece of wire, with HF skin
effect, to the comms signal. I believe that with the PLT internet
trials, the injection points were at central substations, so I guess
that this must have been working at up to at least the local 11kV
distribution level. Just as an aside, I think that the grid and
supergrid operate at 275kV and 400kV, not 475kV. I also have a dim
recollection of reading somewhere, that the 25kV overhead lines on the
uk rail nework, were also used for HF telemetry, but again, I could be
going off on one there. Suffering from CRAFTs disease, don'tcha know
... !! d;~}

FWIW Barry Fox had an article in the current HFN. There are still companies
trying to use EM signals (not wrapped optical fiber) to send data along the
mains to houses. He was trying to warn audio makers, fans, etc, to object
to this as it might cause some problems. The reason being as others have
indicated - that it is inherently a poor route for such signals, so they
will need to 'shout' to get it to work, thus causing problems to people who
don't want it. However I suspect this will be more of a problem for radio
than for things like amplifiers or CD players *if* it actually succeeds and
is at a high enough level to be a pest.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html