[John Fields]

On Thu, 08 May 2008 14:11:27 -0400, Spehro Pefhany
wrote:

On Wed, 07 May 2008 07:54:21 -0500, John Fields
wrote:

On Wed, 7 May 2008 11:26:08 +1000, "Phil Allison"
wrote:

"John Fields"


so why do you find it necessary to abuse your lessors?


** Have you stopped beating your wife?

---
Hardly a parallel since your propensity toward abuse is public
knowledge and your claim that I have ever beaten my wife is imaginary.

Interesting, though, that you equate 'lessor' with 'wife'...

Maybe his wife is also his landlady-- or did you mean "lessers"?

;-)

---
Yup. I thought it looked funny, I should have looked it up.

Thanks! :-)

JF

[Chris Siz]

On Tue 06 May 2008 03:23:10, Michael A. Terrell wrote:


Earl Kiosterud wrote:

It's usually rf currents conducted through the shield conductor,
through the guts of the device being fed that cause the problem.
It isn't rf across the input. A plain piece of wire connected to
the ground of the input can often still cause rf pickup. The
cable's just an antenna connected to the ground of the device.
Shielding doesn't matter. I've seen it in everything from little
(amplified) computer speakers to pro audio mixers. The fix is
almost always to not allow the rf currents to flow through ground
(or any) conductors in the audio circuitry before they get to
other external cables and such tied to the device at other
points in the circuitry. Tying the input and output cables,
chassis, etc. to one point is usually effective. Failing that,
get each cable's ground (balanced or not) at least straight to
the chassis, if not one point -- but never to circuit paths
inside the unit where things like op-amps with huge open-loop
gains can get all weird and demodulate it. There's "pro" audio
gear around (mixers, etc) with susceptibility to rf currents.


I was in the commercial sound business for over a decade, and
never
had any of my installations pick up a radio, CB, or public service
radio. I am now disabled, but I was a broadcast engineer
installing audio equipment in some of the worst environments
possible At one site I had to drive a ground rod over 80 feet,
through Alaska's permafrost to get a better ground. I had the AM
BCB transmitter's signal riding on every 'ground' in the complex.
You could even see it in the video baseband of the TV station at
that site. I removed a couple miles of substandard, and excess
cabling to clean up that mess. Some 'engineer' had paralleled the
two audio boards at one time, then left the cables hooked to one
of the boards after some upgrade. It was really crappy two
conductor, tinned braid, no jacket garbage that was so corroded
that the shield was useless. If the radio station's audio console
hadn't been the original 1948 Gates, with transformer input, the
station would have been useless.

Any 'pro' gear that is susceptible to RF problems is nothing
more
than over hyped consumer crap. A two hole ferrite bead, and a 100
pF disk capacitor made a decent low pass filter for non
transformer balanced inputs. Any equipment with unbalanced inputs
is just consumer crap, no matter what you pay for it.


Hey, steady on old chap! I'm a consumer. Equipment made to suit my
consumer needs may not seem quit so crap to me or other consumers.
Perhaps it's crap to a pro but not to me!

But I'm not a pro and can't afford pro gear and probably have no need
for something very highly specified.

[Michael A. Terrell]

Chris Siz wrote:

Hey, steady on old chap! I'm a consumer. Equipment made to suit my
consumer needs may not seem quit so crap to me or other consumers.
Perhaps it's crap to a pro but not to me!

But I'm not a pro and can't afford pro gear and probably have no need
for something very highly specified.


When you are the engineer at a TV station where you have zero allowed
downtime, and equipment in five sepearte locations to maintain, consumer
stuff _IS_ crap. I had agroup that won a FCC construction permit for a
low power UHF TV station. They actually thought that they could go on
the air with used camcorders and a cheap, unbalanced mic mixer from
Radio Shack.


--
http://improve-usenet.org/index.html


Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm

[Grimly Curmudgeon]

Kevin McMurtrie wrote:

There are a few differences. TV coax will work in some conditions but
not generally.

TV coax is very brittle. The inner wire is copper-plated steel and the
outer shield is aluminum wire and aluminum foil. It will quickly crack
where it meets the connectors.

TV coax may not pass small audio signals well because of its aluminum
shield. Aluminum is extremely reactive so it is always coated with a
thin oxide layer. Higher voltages can spark through it and TV RF can
capacitively couple through it. Microphone signals might become
distorted. Cable for lower frequencies uses copper shielding.

Good microphone and instrument cable has an insulation that drains away
static electrical charges. RF coax can contain electrical charges in
the insulation that causes it to act like condenser microphone.

stands back in amazement

You know, I don't think I've seen such a collection tripe in a single
post for at least a week. Well done.

To the OP: Give it a go - it's free, and if it works, fine, you won't
harm anything.
--
Dave
GS850x2 XS650 SE6a

"It's a moron working with power tools.
How much more suspenseful can you get?"
- House

[Ian Jackson]

In message , Grimly Curmudgeon
writes
Kevin McMurtrie wrote:

There are a few differences. TV coax will work in some conditions but
not generally.

TV coax is very brittle. The inner wire is copper-plated steel and the
outer shield is aluminum wire and aluminum foil. It will quickly crack
where it meets the connectors.

TV coax may not pass small audio signals well because of its aluminum
shield. Aluminum is extremely reactive so it is always coated with a
thin oxide layer. Higher voltages can spark through it and TV RF can
capacitively couple through it. Microphone signals might become
distorted. Cable for lower frequencies uses copper shielding.

Good microphone and instrument cable has an insulation that drains away
static electrical charges. RF coax can contain electrical charges in
the insulation that causes it to act like condenser microphone.

stands back in amazement

You know, I don't think I've seen such a collection tripe in a single
post for at least a week. Well done.

To the OP: Give it a go - it's free, and if it works, fine, you won't
harm anything.

There is one point which definitely has validity. Without checking, I
recall that electrostatic charges can build up in the dielectric, and
this causes a 'rustling' sound when the coax is bent. I believe that
some coax - where this problem has been minimised - is specced
specifically as being 'non-microphonic'. A Google is called for.
--
Ian

[Don Pearce]

On Sat, 10 May 2008 13:28:16 +0100, Ian Jackson
wrote:

In message , Grimly Curmudgeon
writes
Kevin McMurtrie wrote:

There are a few differences. TV coax will work in some conditions but
not generally.

TV coax is very brittle. The inner wire is copper-plated steel and the
outer shield is aluminum wire and aluminum foil. It will quickly crack
where it meets the connectors.

TV coax may not pass small audio signals well because of its aluminum
shield. Aluminum is extremely reactive so it is always coated with a
thin oxide layer. Higher voltages can spark through it and TV RF can
capacitively couple through it. Microphone signals might become
distorted. Cable for lower frequencies uses copper shielding.

Good microphone and instrument cable has an insulation that drains away
static electrical charges. RF coax can contain electrical charges in
the insulation that causes it to act like condenser microphone.

stands back in amazement

You know, I don't think I've seen such a collection tripe in a single
post for at least a week. Well done.

To the OP: Give it a go - it's free, and if it works, fine, you won't
harm anything.

There is one point which definitely has validity. Without checking, I
recall that electrostatic charges can build up in the dielectric, and
this causes a 'rustling' sound when the coax is bent. I believe that
some coax - where this problem has been minimised - is specced
specifically as being 'non-microphonic'. A Google is called for.

Yup, the search term you need is the triboelectric effect. It is a
surface phenomenon that can affect dielectric materials. The usual
cure in non-microphonic cables is a layer of moderate conductivity -
usually thin and black - just inside the outer screen.

d
--
Pearce Consulting
http://www.pearce.uk.com

[JosephKK[_2_]]

On Sat, 10 May 2008 13:23:41 GMT, (Don Pearce)
wrote:

On Sat, 10 May 2008 13:28:16 +0100, Ian Jackson
wrote:

In message , Grimly Curmudgeon
writes
Kevin McMurtrie wrote:

There are a few differences. TV coax will work in some conditions but
not generally.

TV coax is very brittle. The inner wire is copper-plated steel and the
outer shield is aluminum wire and aluminum foil. It will quickly crack
where it meets the connectors.

TV coax may not pass small audio signals well because of its aluminum
shield. Aluminum is extremely reactive so it is always coated with a
thin oxide layer. Higher voltages can spark through it and TV RF can
capacitively couple through it. Microphone signals might become
distorted. Cable for lower frequencies uses copper shielding.

Good microphone and instrument cable has an insulation that drains away
static electrical charges. RF coax can contain electrical charges in
the insulation that causes it to act like condenser microphone.

stands back in amazement

You know, I don't think I've seen such a collection tripe in a single
post for at least a week. Well done.

To the OP: Give it a go - it's free, and if it works, fine, you won't
harm anything.

There is one point which definitely has validity. Without checking, I
recall that electrostatic charges can build up in the dielectric, and
this causes a 'rustling' sound when the coax is bent. I believe that
some coax - where this problem has been minimised - is specced
specifically as being 'non-microphonic'. A Google is called for.

Yup, the search term you need is the triboelectric effect. It is a
surface phenomenon that can affect dielectric materials. The usual
cure in non-microphonic cables is a layer of moderate conductivity -
usually thin and black - just inside the outer screen.

d

Yep. In extreme cases they use silver powder as well. It gets
Expen$ive. Takes really expensive connectors. Mebbe over $100 a pop by
now. Not to mention several $k for the tool kit and training to use
them.