Mains filters
 

"Arfa Daily" wrote in message
...

"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
The high-power UHF TV Transmitters in the UK are 50kW, mostly PyeTVT/Harris
with a number of Marconi as well. The difference between the Tx power and
ERP is entirely made up of antenna gain. UHF antennas have a very narrow
beam, tilted downwards, as there's no point sending power off into space.
The beam is sufficiently narrow so that the signal close to the mast is
actually less than at a distance, also avoiding people's receivers from
overloading.

I don't know how many Klystrons are left in UK service, I would guess a fair
few. Channel 5 was engineered right from the start with Solid State
transmitters, of , if I remember correctly 10kW power, Channel 4 was
klystron originally.

S.

Mains filters
 

Jim Lesurf wrote:

That mains filters may be useful if you are having a problem with
audible 'clicks and pops' from the mains, and can't suppress them at
source.

What about inaudible RF interference, for example from a PC PSU?

I know all about the regulations... but I've opened enough of these
things up to know that they often radiate like a spark transmitter.

Ideally, though, the audio equipment is well enough designed to
prevent such problems being audible.

In an ideal world, yes... but even kit like my Arcam stuff is still
built to a budget. I've had long conversations with R&D bods from
companies like Arcam, Meridian etc at hi-fi shows, and they're always
cursing the beancounters... "we wanted to put more RFI filtering in, but
budget constraints meant we had to make sacrifices" etc etc.

However, simply chainging 'mains cable' with no filter or surge
suppressor is probably a waste of effort.

Yup... if you replaced your IEC cable with 3-core braided cable with
screening, all you'd be doing is making sure the RFI got from one end to
the other with minimal losses!

Been doing a bit of research today, and I've located something called an
Isotek cable. A friend at Sevenoaks hi-fi has offered to bring one
around (the one they use in their demo room) to find out if it makes a
difference, and if so, how it works, what type of filter it uses etc.

I've managed to source some braided 3 core screened cable that's rated
for mains use and only costs about £4/m, filtered plug less than £2, IEC
line socket about £1.20. If it does make a difference, I'm going to have
a go at making my own for about 8 quid instead of the 60 quid an Isotek
cable costs. Then sell my own ones for 50-60 quid. ;-)

Will post the results of my testing after the weekend - I can't get hold
of the loan cable until Sunday as they'll need it in the demo room on
Saturday.

--
Glenn Richards Tel: (01453) 845735
Squirrel Solutions http://www.squirrelsolutions.co.uk/

IT consultancy, hardware and software support, broadband installation

Mains filters
 

"Serge Auckland" wrote in message
...

"Arfa Daily" wrote in message
...

"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
The high-power UHF TV Transmitters in the UK are 50kW, mostly
PyeTVT/Harris with a number of Marconi as well. The difference between the
Tx power and ERP is entirely made up of antenna gain. UHF antennas have a
very narrow beam, tilted downwards, as there's no point sending power off
into space. The beam is sufficiently narrow so that the signal close to
the mast is actually less than at a distance, also avoiding people's
receivers from overloading.

I don't know how many Klystrons are left in UK service, I would guess a
fair few. Channel 5 was engineered right from the start with Solid State
transmitters, of , if I remember correctly 10kW power, Channel 4 was
klystron originally.

S.

Thanks Tony and Serge. All interesting stuff. When S.H. UHF was first put
into service, I was an apprentice in the TV trade, and the Rediffusion
branch that I worked for, was chosen to do field strength monitoring by the
IBA, I think it was. Their boys left a receiver with us, with a chart
recorder attached. It was my job to check the tuning of it every morning.
Then it got hit by lightning as I recall, and the very expensive feeder from
Sweden or some such place, got fried. I seem to think that a substitute
piece of pipe from somewhere was put in place to get the site going again,
but there was some VSWR issue with it, because it was a few feet too short
and had to be joined, and whenever the antennas iced up a bit, the SWR seen
by the tx would go just a bit too far out of spec, and the auto protection
would pull it off the air. That tx was never as good after ... Happy days
!! ;-)

Arfa

Mains filters
 

In article , Glenn Richards
writes
Jim Lesurf wrote:

That mains filters may be useful if you are having a problem with
audible 'clicks and pops' from the mains, and can't suppress them at
source.

What about inaudible RF interference, for example from a PC PSU?

I know all about the regulations... but I've opened enough of these
things up to know that they often radiate like a spark transmitter.

Ideally, though, the audio equipment is well enough designed to
prevent such problems being audible.

In an ideal world, yes... but even kit like my Arcam stuff is still
built to a budget. I've had long conversations with R&D bods from
companies like Arcam, Meridian etc at hi-fi shows, and they're always
cursing the beancounters... "we wanted to put more RFI filtering in, but
budget constraints meant we had to make sacrifices" etc etc.

However, simply chainging 'mains cable' with no filter or surge
suppressor is probably a waste of effort.

Yup... if you replaced your IEC cable with 3-core braided cable with
screening, all you'd be doing is making sure the RFI got from one end to
the other with minimal losses!

Been doing a bit of research today, and I've located something called an
Isotek cable. A friend at Sevenoaks hi-fi has offered to bring one
around (the one they use in their demo room) to find out if it makes a
difference, and if so, how it works, what type of filter it uses etc.

I've managed to source some braided 3 core screened cable that's rated
for mains use and only costs about £4/m, filtered plug less than £2, IEC
line socket about £1.20. If it does make a difference, I'm going to have
a go at making my own for about 8 quid instead of the 60 quid an Isotek
cable costs. Then sell my own ones for 50-60 quid. ;-)

Don't forget the bit of twin and earth to the consumer unit and the lump
of wire to the substation, and the HV stuff feeding that;-)


Will post the results of my testing after the weekend - I can't get hold
of the loan cable until Sunday as they'll need it in the demo room on
Saturday.

Actually why don't you make some up, get some real bull**** speak on a
flashy website sell 'em for a least ten times what the price was you
made them at, and I'll bet you'll find some feeble minded wallies to
sell them to.

And BTW give us 10% for putting the idea in your head wontcha;-))




--
Tony Sayer

Mains filters
 

In article ,
Arny Krueger 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.

Most such interference probably does not come in via the power supply or
component power cord.


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

It's probably the clean ground that's providing any noticable benefit.
It's pretty hard to make up a clean ground with a line cord filter.

Yup. The easiest way to get a 'clean' mains supply for audio. Standard
practice in studios.

--
*If we weren't meant to eat animals, why are they made of meat?

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

Mains filters
 

tony sayer wrote:

Don't forget the bit of twin and earth to the consumer unit and the
lump of wire to the substation, and the HV stuff feeding that;-)

Heh...

Except that's *upstream* of the filter, so... as long as you're not
picking up RF interference on the cable between the filter and the back
of your equipment I'm guessing the actual mains cable doesn't matter too
much.

That said, if you've got the amount of RF-radiating crap in your house
that I have... it's probably worth wrapping tinfoil around the power
cables... and around your head as well so your brain doesn't get microwaved.

Will post the results of my testing after the weekend - I can't get
hold of the loan cable until Sunday as they'll need it in the demo
room on Saturday.
Actually why don't you make some up, get some real bull**** speak on
a flashy website sell 'em for a least ten times what the price was
you made them at, and I'll bet you'll find some feeble minded wallies
to sell them to.

Had actually thought of that. In fact, I came up with the idea of using
Arctic grade flex (it's blue, so it looks pretty) with a filtered plug
and a decent quality IEC connector, cost around £5, could sell 'em for
about £50. Or if they actually *do* make a difference to the sound, £100.

And BTW give us 10% for putting the idea in your head wontcha;-))

Heh, I'd already had that idea. :-P

--
Glenn Richards Tel: (01453) 845735
Squirrel Solutions http://www.squirrelsolutions.co.uk/

IT consultancy, hardware and software support, broadband installation

Mains filters
 

In article , Glenn
Richards writes
tony sayer wrote:

Don't forget the bit of twin and earth to the consumer unit and the
lump of wire to the substation, and the HV stuff feeding that;-)

Heh...

Except that's *upstream* of the filter, so... as long as you're not
picking up RF interference on the cable between the filter and the back
of your equipment I'm guessing the actual mains cable doesn't matter too
much.

That said, if you've got the amount of RF-radiating crap in your house
that I have... it's probably worth wrapping tinfoil around the power
cables... and around your head as well so your brain doesn't get microwaved.

Sell that to them as well. Tinfoil beanie hats..

Will post the results of my testing after the weekend - I can't get
hold of the loan cable until Sunday as they'll need it in the demo
room on Saturday.
Actually why don't you make some up, get some real bull**** speak on
a flashy website sell 'em for a least ten times what the price was
you made them at, and I'll bet you'll find some feeble minded wallies
to sell them to.

Had actually thought of that. In fact, I came up with the idea of using
Arctic grade flex (it's blue, so it looks pretty) with a filtered plug
and a decent quality IEC connector, cost around £5, could sell 'em for
about £50. Or if they actually *do* make a difference to the sound, £100.

Nope.. the higher you price them, the more the gullible will believe
they should have them, as they will then feel need them even more and
cos their more expensive they must be better right;?...

And BTW give us 10% for putting the idea in your head wontcha;-))

Heh, I'd already had that idea. :-P

15% now snip eh?...


--
Tony Sayer

Mains filters
 

"tony sayer" wrote in message

Rane, a U.S. pro audio gear manufacturer with a very
solid reputation for conservative technology claims that
some of their gear (like mic preamps) showed a SNR
advantage when the power transformer was moved out of
the box and into a big plastic wart on the power cord.

http://www.rane.com/rap.html

Reasons to use external pwoer supples:

"Better Audio Performance. Removes the hum source, i.e.
the AC line transformer and all primary circuits
resulting in quieter noise performance, without the
usual (and annoying) 50/60 Hz and 150/180 Hz hum
components."

More bollockx.

**** poor design then, if their having those problems.

Mic preamps for audio production are a more stringent environment than say,
RIAA phono preamps. RIAA MM phono preamps have 40 dB gain at 20Hz, but their
noise bandwidth is only 50 Hz. Mic preamps typically have up to 60 dB of
gain, and a minimum of 20 KHz noise bandwidth, usually far more.

This "wall-wart" caper is more to do with complying with
different regs in different markets...

That, too.

Mains filters
 

Hi,

"Glenn Richards" wrote in message
. uk...

That said, if you've got the amount of RF-radiating crap in your house
that I have... it's probably worth wrapping tinfoil around the power
cables... and around your head as well so your brain doesn't get
microwaved.

You'd be doing well to have more RF noise in your house than I have,
and mains filters here do nothing that I can hear.

We have 3 802.11g access points, radio phone and pager system, wireless
TV senders, upwards of ten PCs and a bunch of other electrically noisy
stuff
(we're a bit geeky). When we moved in I got the 'shed' (listening room)
rewired,
and in the process borrowed some filtered 'multi-way' adapters. I spent
an entire
weekend wiring and listening, and could hear absolutely no difference
when they
were in circuit. YMMV.

Heh, I'd already had that idea. :-P

You're not the first, and you won't be the last :-)

Regards,

Glenn.

Mains filters
 

"Glenn Booth" wrote in message
...
Hi,

"Glenn Richards" wrote in message
. uk...

That said, if you've got the amount of RF-radiating crap in your house
that I have... it's probably worth wrapping tinfoil around the power
cables... and around your head as well so your brain doesn't get
microwaved.

You'd be doing well to have more RF noise in your house than I have,
and mains filters here do nothing that I can hear.

We have 3 802.11g access points, radio phone and pager system, wireless
TV senders, upwards of ten PCs and a bunch of other electrically noisy
stuff
(we're a bit geeky). When we moved in I got the 'shed' (listening room)
rewired,
and in the process borrowed some filtered 'multi-way' adapters. I spent an
entire
weekend wiring and listening, and could hear absolutely no difference when
they
were in circuit. YMMV.

Heh, I'd already had that idea. :-P

You're not the first, and you won't be the last :-)

Regards,

Glenn.


I think there is a point being missed he- Mains filtering won't "make
the audio sound better", but it will remove impulsive interference like
motor switching spikes if any are present. If you do an A-B comparison
before and after installing any filtering, you *won't* hear any difference
unless just at the time you were doing the tests, the farmer next door
switches off his milking machine, or the spot-welder at the blacksmith down
the lane goes off. Closer to home, fridge compressors and central heating
pumps can put splats on the mains, and whilst I would always suggest
suppression at source, that might not be possible if the offending item is
in your neighbour's house, or the next flat.

The avoidance of mains-borne clicks or equipment lock-ups is the main
function of domestic mains filtering. All other suggestions of improvements
in the sound are snake-oil, put about by those selling expensive filtering
items.

S.