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Chris Siz Chris Siz is offline
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Default OK to use TV coax for microphone?

I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


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Don Pearce Don Pearce is offline
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Default OK to use TV coax for microphone?

On Sat, 03 May 2008 10:58:27 +0100, Chris Siz
wrote:

I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


If you can get hold of some better cable do so. You have two problems
here - first coax isn't balanced, which is sort of bad news for tiny
signals such as you get from a mic. And secondly, to compound that, if
you strip back a little of the outer sheath, you will find that the
screen is 90% holes - in other words, the cable is just about
unscreened.

As for using it for UHF TV, go ahead - that is what it is meant for,
and 10 meters is just about the maximum run length before you need to
think about using something better.

d

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Ian Jackson Ian Jackson is offline
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Default OK to use TV coax for microphone?

In message , Chris Siz
writes
I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


While you might get away with using your cable, good screening/shielding
becomes increasing important at the lower frequencies, as the
interfering signals (on the outside of the coax) penetrate more easily
through the outer shield. Well-screened audio would be better. In many
cases, 'flimsy' screening may be adequate at UHF (and the cable may have
low loss) but, again, well-screened cable will be better for preventing
interference. Maybe it's a case of try it and see what happens?
--
Ian
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Theo Theo is offline
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Default OK to use TV coax for microphone?


"Ian Jackson" wrote in message
...
In message , Chris Siz
writes
I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


While you might get away with using your cable, good screening/shielding
becomes increasing important at the lower frequencies, as the
interfering signals (on the outside of the coax) penetrate more easily
through the outer shield. Well-screened audio would be better. In many
cases, 'flimsy' screening may be adequate at UHF (and the cable may have
low loss) but, again, well-screened cable will be better for preventing
interference. Maybe it's a case of try it and see what happens?


I would have thought the converse to be true, surely the "holes" in the
screening
braid would be less of a problem at audio frequencies than at UHF?
I am thinking in terms of wavelength.


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Bob Eld Bob Eld is offline
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Default OK to use TV coax for microphone?


"Chris Siz" wrote in message
...
I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


Yes, it's OK to use coax for a mic cable assuming the mic is a single ended
connection (one wire) with ground. The biggest issue is the cable
capacitance. Depending on the mic's impedance, this capacitance will
attenuate high frequencies. A low impedance mike will work better than a
high impedance mic. The accumulated capacitance in four meters of cable will
be a couple of hundred pico-farads, probably not a problem.

For UHF TV cables are usually 72 ohms. If your cable is 72 ohms, it's
probably OK. If it is 50 ohms it will still work but may degrade the picture
quality because of reflections within the cable. Try and see. If the antenna
is 300 ohms, the cable is not suitable unless matched with a balun or other
impedance matching device.




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Default OK to use TV coax for microphone?

On May 3, 4:58 am, Chris Siz wrote:
I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?

--

[x-posted to 3 relevant groups]


Isn't coax kind of rigid? Will the microphone need to move around?
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Ian Jackson Ian Jackson is offline
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Default OK to use TV coax for microphone?

In message , Bob Eld
writes

"Chris Siz" wrote in message
...
I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


Yes, it's OK to use coax for a mic cable assuming the mic is a single ended
connection (one wire) with ground. The biggest issue is the cable
capacitance. Depending on the mic's impedance, this capacitance will
attenuate high frequencies. A low impedance mike will work better than a
high impedance mic. The accumulated capacitance in four meters of cable will
be a couple of hundred pico-farads, probably not a problem.


Out of interest, how does the capacitance of ordinary TV coax (which
will be 75 ohms, of course) compare with 'proper' mic cable? Of course,
a lot of audio is balanced (usually nominally 600 ohms), which makes
things generally less prone to the pick-up of interference. Unbalanced
connections via coax (even if proper screened audio cable) is
less-tolerant.

For UHF TV cables are usually 72 ohms. If your cable is 72 ohms, it's
probably OK. If it is 50 ohms it will still work but may degrade the picture
quality because of reflections within the cable.
Try and see.


As it's TV coax, it's unlikely to be 50 ohms.

If the antenna
is 300 ohms, the cable is not suitable unless matched with a balun or other
impedance matching device.


UK aerials are not 300 ohms (except for those indoor FM radio aerials
made from 300 twin feeder). I believe that, these days, they are also a
bit of rarity in the USA.
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Martin Griffith Martin Griffith is offline
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Default OK to use TV coax for microphone?

On Sat, 3 May 2008 17:01:19 +0100, in sci.electronics.design Ian
Jackson wrote:


Out of interest, how does the capacitance of ordinary TV coax (which
will be 75 ohms, of course) compare with 'proper' mic cable? Of course,
a lot of audio is balanced (usually nominally 600 ohms), which makes
things generally less prone to the pick-up of interference. Unbalanced
connections via coax (even if proper screened audio cable) is
less-tolerant.


600 ohms is dead and buried, for the audio world.The only time it is
mentioned is in data sheets, "will drive XXdB into 600R" etc


martin
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Kevin McMurtrie Kevin McMurtrie is offline
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Default OK to use TV coax for microphone?

In article ,
Chris Siz wrote:

I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


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.

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SteveE SteveE is offline
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Default OK to use TV coax for microphone?

Kevin McMurtrie wrote:
In article ,
Chris Siz wrote:

I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't want
an impaired audio signal. The length I need to use is 3 to 4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


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.

Not necessarily in fact a lot of TV coax is entirely copper.

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.


Yes, the laws of nature decided that.
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.


Rubbish.

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.


Rubbish again. Where do you get this knowledge from?

Steve

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Default OK to use TV coax for microphone?

On Sat, 03 May 2008 19:39:45 +0100, Walt Davidson
wrote:

On Sat, 03 May 2008 11:05:41 -0700, Kevin McMurtrie
wrote:

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.


What planet do you live on? I have never seen TV coax as you
describe. Coax with copper-plated steel inner conductor is mostly
used as data cable (ethernet).

73 de G3NYY


The stuff with foil is higher quality, used mostly for satellite dish
feeder. TV coax is just a copper inner with about half a dozen fine
strands for a screen.

d

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Default OK to use TV coax for microphone?


Say no to ISPs selling your private browsing history to advertisers who
will then send you targeted adverts, as well as, potentially, compromising
your security on line.


so that is why I get so much porno spam .......


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Dave Platt Dave Platt is offline
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Default OK to use TV coax for microphone?

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.


What planet do you live on? I have never seen TV coax as you
describe. Coax with copper-plated steel inner conductor is mostly
used as data cable (ethernet).


75-ohm with copper-coated steel center conductor is often used for
outdoor cable-company coax runs. The steel core gives it enough
tensile strength to allow long runs to hang between poles (and between
pole and house) without stretching. This stuff is often a "hardline"
coax, with an aluminum outer shield... very low RF leakage, which is
an important issue for cable companies.

Indoor TV coax is sometimes RG-59, sometimes RG-6. It usually seems
to have a solid-copper center conductor (to allow for termination via
a crimp-on F connector). The shield may be anything from one layer of
braid with poor coverage, up to a quad shield (two layers of braid,
two layers of foil). It may be fairly stiff.

Coax which is optimized for microphone usage tends to be relatively
flexible (stranded center conductor, compliant jacket), and I
understand that the better varieties are designed to minimize the
generation of triboelectric noise (which occurs when the cable is
moved, as a result of static or piezoelectric effects).

Using TV coax for a microphone ought not to be harmful, but it's
probably not the best choice, and I'd do it only if a limited budget
made it impossible to get something better suited to the purpose.

Useful reference: http://www.belden.com/pdfs/Techpprs/tpbroad.htm

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Default OK to use TV coax for microphone?

jim stewart wrote:
Say no to ISPs selling your private browsing history to advertisers who
will then send you targeted adverts, as well as, potentially, compromising
your security on line.


so that is why I get so much porno spam .......


Well only you can answer that Jim ;-)

But you are off the hook with Phorm as they promise not to profile that
sort of stuff.

That promise seems a bit hollow as Phorm, previously known as 121 media
were involved in malware (people on page) before this. I wouldn't trust
them one bit.

Steve

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and please sign the rapidly growing on line petition at
http://petitions.pm.gov.uk/ispphorm/ if you don't want to see this
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Les. Les. is offline
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Default OK to use TV coax for microphone?


"Martin Griffith" wrote in message
...
On Sat, 3 May 2008 17:01:19 +0100, in sci.electronics.design Ian
Jackson wrote:

600 ohms is dead and buried, for the audio world.The only time it is
mentioned is in data sheets, "will drive XXdB into 600R" etc


martin


Quite so. The concept of matching a microphone's impedance to get the best
power transfer has not been practiced for a considerable time.
Modern dynamic mics expect to look at a "bridging" impedance e.g. around 10K
for a mic having a Z of 150-200 Ohms and to operate as a voltage, rather
than a power source.
The characteristic imedance of the feeder (over a few feet) may thus be
disregarded.


Les.




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Ian Thompson-Bell Ian Thompson-Bell is offline
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Default OK to use TV coax for microphone?

Les. wrote:
"Martin Griffith" wrote in message
...
On Sat, 3 May 2008 17:01:19 +0100, in sci.electronics.design Ian
Jackson wrote:
600 ohms is dead and buried, for the audio world.The only time it is
mentioned is in data sheets, "will drive XXdB into 600R" etc


martin


Quite so. The concept of matching a microphone's impedance to get the best
power transfer has not been practiced for a considerable time.
Modern dynamic mics expect to look at a "bridging" impedance e.g. around 10K
for a mic having a Z of 150-200 Ohms and to operate as a voltage, rather
than a power source.


No they expect to see 1K2 to 2K not 10K and that is what most pro mic
pres provide. 10K input impedance is for bridging line levels.

Cheers

Ian
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Dead Paul Dead Paul is offline
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Default OK to use TV coax for microphone?

On Sat, 03 May 2008 19:39:45 +0100, Walt Davidson wrote:

On Sat, 03 May 2008 11:05:41 -0700, Kevin McMurtrie
wrote:

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.


What planet do you live on? I have never seen TV coax as you describe.
Coax with copper-plated steel inner conductor is mostly used as data cable
(ethernet).


You want to see the crap which passes for rg58 at maplin electronics.




73 de G3NYY


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/ // / _// __ |/ // / / ___/ __ / /_/ / /__
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Default OK to use TV coax for microphone?

On Sat, 03 May 2008 18:41:27 +0000, Don Pearce wrote:

On Sat, 03 May 2008 19:39:45 +0100, Walt Davidson
wrote:

On Sat, 03 May 2008 11:05:41 -0700, Kevin McMurtrie
wrote:

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.


What planet do you live on? I have never seen TV coax as you describe.
Coax with copper-plated steel inner conductor is mostly used as data
cable (ethernet).

73 de G3NYY


The stuff with foil is higher quality, used mostly for satellite dish
feeder. TV coax is just a copper inner with about half a dozen fine
strands for a screen.


Yes, and i've seen rg58 like that at maplin electronics!

Just for your information :-)


d


--
___ _______ ___ ___ ___ __ ____
/ _ \/ __/ _ | / _ \ / _ \/ _ |/ / / / /
/ // / _// __ |/ // / / ___/ __ / /_/ / /__
/____/___/_/ |_/____/ /_/ /_/ |_\____/____/

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Michael A. Terrell Michael A. Terrell is offline
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Default OK to use TV coax for microphone?


Walt Davidson wrote:

On Sat, 03 May 2008 11:05:41 -0700, Kevin McMurtrie
wrote:

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.


What planet do you live on? I have never seen TV coax as you
describe. Coax with copper-plated steel inner conductor is mostly
used as data cable (ethernet).



Then you've never seen the wire used by cable TV and Satellite TV
companies. Pure copper is too expensive these days, and too soft for
repeated flexing. If you want to pay over a dollar a foot for copper
core TV coax, go ahead. The last time I had to buy some it was about
eight times the price of the foil shield W/braid TV coax, and useless
for UHF. Use a magnet, and see for yourself. The copper plating smears
when cut with dykes, and makes the coated steel appear to be solid
copper.


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Default OK to use TV coax for microphone?

In article ,
Walt Davidson wrote:

On Sat, 03 May 2008 11:05:41 -0700, Kevin McMurtrie
wrote:

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.


What planet do you live on? I have never seen TV coax as you
describe. Coax with copper-plated steel inner conductor is mostly
used as data cable (ethernet).

73 de G3NYY


It's all I've ever seen for RG-6 TV cabling. Try sanding the tip to see
if it turns silver, or use a magnet.
http://en.wikipedia.org/wiki/RG-6

It's really a TV-only thing. Copper plated steel wire won't work for
many applications.

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Jeff Liebermann Jeff Liebermann is offline
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Default OK to use TV coax for microphone?

On Sat, 03 May 2008 21:23:08 -0400, "Michael A. Terrell"
wrote:

Then you've never seen the wire used by cable TV and Satellite TV
companies. Pure copper is too expensive these days, and too soft for
repeated flexing. If you want to pay over a dollar a foot for copper
core TV coax, go ahead. The last time I had to buy some it was about
eight times the price of the foil shield W/braid TV coax, and useless
for UHF. Use a magnet, and see for yourself. The copper plating smears
when cut with dykes, and makes the coated steel appear to be solid
copper.


Well, I did just that. I grabbed a magnet off the fridge and went
through my pile of RG-6/u CATV coax jumpers and cables. The really
old stuff had an all copper center conductor. The fairly current
stuff has a copperweld or CCS (copper clad steel) center conductor. I
would guess that about 90% of what's in the pile (about 100 cables) is
CCS. Amazing:
http://www.fushiinternational.com/Products.aspx?p=Bimetallic
http://www.fushiinternational.com/Pr...spx?p=CCSCable

However, much of the RG-6/u cable is "satellite grade", which means it
should work to about 2GHz with minimal loss. I've been using the quad
shielded variety (apparently with a CCS center conductor) for years
for Wi-Fi at 2.4GHz with about 10dB/100ft attenuation (measured). The
loss is in the dielectric, not in the center conductor cladding. I
would say that it works just fine at UHF (300-3000MHz).

Incidentally, I blundered across this data sheet for RG-6/u. They can
make it just about any way you want it, and still call it RG-6/u. Note
the line with:
6) Braiding coverage: Between 30 - 97% available;
I can't imagine who would want to buy 30% coverage outer shielding.
http://www.tootoo.com/supplier/product-detail/6251149/RG6%252fU.html

As for the coax being brittle, that's possible if it were plenum rated
cable for running through air ducts. The stuff is suppose to be "low
smoke" when burning. It tends to be rather stiff and brittle. For
RG-6/u, the flexibility is largely in the type of braid and outer
jacket. Quad shielded is going to be rather stiff. Judging by the
mixture in my junk box, I have cables that range from super flexible
(for the back of HDTV installs) to super stiff (gel filled for direct
burial). Your mileage and stiffness may vary.

As for the suitability as a microphone cable, I dunno. The original
posting had no useful descriptions of the microphone, the found cable,
or the equipment to which it will be connected. 4.8mm O.D. could be a
wide variety of possible coax cables. I'm lazy and don't wanna guess.


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Richard Crowley Richard Crowley is offline
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Default OK to use TV coax for microphone?

"SteveE" wrote ...
Kevin McMurtrie wrote:
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.


Rubbish.


Indeed. Take it out with the rest of the trash.

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.


Rubbish again. Where do you get this knowledge from?


Looks like a reference to some hi-Z cable that is made with condctive
fabric (or other such substance) to reduce the cable microphonic
tendencies due to the triboelectric effect of some kinds of dielectric
insulation.


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Richard Crowley Richard Crowley is offline
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Default OK to use TV coax for microphone?

"Chris Siz" wrote ...
I am in the UK and have a 10m length of some cheap TV aerial coax. It
came from a discount store as a TV coax extension cable. I measure the
cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone?


Not enough details to answer your question adequately.
First of all, the kinds of microphones used for audio
applications (reinforcement, recording, etc.) are usually
balanced and require cable with two inner wires and an
outside shield/screen. If you are trying to use a balanced
mic, then the cable is unsuitable because it is unbalanced.

So, the biggest question is WHAT microphone?
Equally helpful would be to reveal what it plugs in to.

I don't want an impaired audio signal.


"impairment" of the audio signal is unlikely to occur,
and is probably not an issue here.

The length I need to use is 3 to 4 metres.


Not really important to the question. It wouldn't make
much difference if it were 1 m or 1Km

Note that even if you need unbalanced cable for your
unidentified microphone, typical RF/antenna cable is
very poorly suited for terminating in typical audio-
type connectors. It is frequently aluminum and
unsuitable for any kind of soldering, etc.

(2) Is it ok for UHF TV or is it actually quite low grade
coax and prone to interference or mess up the aerial signal?


Insufficient details to answer that question, also.
There are hundreds of different kinds of antenna-
type (RF) coax. Some of it might be perfect for
UHF TV (whatever that means in your area?)
And other kinds may be completely a disaster.

Again, "interference" is not the most likely mode
of failure of using the wrong kind of cable.


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Jeff Liebermann Jeff Liebermann is offline
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Default OK to use TV coax for microphone?

On Sat, 03 May 2008 21:23:08 -0400, "Michael A. Terrell"
wrote:

Use a magnet, and see for yourself. The copper plating smears
when cut with dykes, and makes the coated steel appear to be solid
copper.


Trivia:
Dike = Diagonal Cutters
http://en.wikipedia.org/wiki/Diagonal_pliers
Dyke = Lesbian
http://en.wikipedia.org/wiki/Dyke_(lesbian)
Dyke or Dike = Earthen wall or dam
http://en.wikipedia.org/wiki/Dike_%28construction%29

Methinks "dikes" would be the correct spelling.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Michael A. Terrell Michael A. Terrell is offline
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Default OK to use TV coax for microphone?

Jeff Liebermann wrote:

However, much of the RG-6/u cable is "satellite grade", which means it
should work to about 2GHz with minimal loss. I've been using the quad
shielded variety (apparently with a CCS center conductor) for years
for Wi-Fi at 2.4GHz with about 10dB/100ft attenuation (measured). The
loss is in the dielectric, not in the center conductor cladding. I
would say that it works just fine at UHF (300-3000MHz).



I was talking about higher losses in a copper braided shield, VS foil
& steel braid. I used to test & specify all the passivies for a major
MSO CATV company.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida


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Phil Allison Phil Allison is offline
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Default OK to use TV coax for microphone?


"Richard Crowley"

(1) Is it ok to use this sort of coax for a microphone?


Not enough details to answer your question adequately.
First of all, the kinds of microphones used for audio
applications (reinforcement, recording, etc.) are usually
balanced and require cable with two inner wires and an
outside shield/screen. If you are trying to use a balanced
mic, then the cable is unsuitable because it is unbalanced.



** Not true at all !!

There is NO reason not to use a (suitable) co-axial type cable with a
microphone - either low or high impedance.

Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables.

Try it out if you don't believe this.



The length I need to use is 3 to 4 metres.


Not really important to the question. It wouldn't make
much difference if it were 1 m or 1Km



** If the mic is high impedance ( ie 50 kohms), then more than 10 metres or
so of cable will cause high frequency response peaking and early roll off as
the cable capacitance loads the transformer inside the mic.

If the mic is low impedance ( ie circa 250 ohms), then hundreds of metres
can be used - but not kilometres.


....... Phil


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Don Pearce Don Pearce is offline
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Default OK to use TV coax for microphone?


Phil Allison wrote:
"Richard Crowley"
(1) Is it ok to use this sort of coax for a microphone?

Not enough details to answer your question adequately.
First of all, the kinds of microphones used for audio
applications (reinforcement, recording, etc.) are usually
balanced and require cable with two inner wires and an
outside shield/screen. If you are trying to use a balanced
mic, then the cable is unsuitable because it is unbalanced.



** Not true at all !!

There is NO reason not to use a (suitable) co-axial type cable with a
microphone - either low or high impedance.

Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables.

Try it out if you don't believe this.


Of course a proper microphone cable is SCREENED balanced twisted pair,
so it enjoys the multiple benefits of electric screening by the outer,
the common mode nature of any residual interference and magnetic
interference cancellation by the twist in the balanced pair. A poorly
screened coax cable such as TV coax has only a part of the first of
those so this claim is clearly nonsensical. If it were true,
professional microphone and mixer companies would not be going to the
trouble of designing balanced kit.



The length I need to use is 3 to 4 metres.

Not really important to the question. It wouldn't make
much difference if it were 1 m or 1Km



** If the mic is high impedance ( ie 50 kohms), then more than 10 metres or
so of cable will cause high frequency response peaking and early roll off as
the cable capacitance loads the transformer inside the mic.



If the mic is low impedance ( ie circa 250 ohms), then hundreds of metres
can be used - but not kilometres.



This is true.

d
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Ian Jackson Ian Jackson is offline
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Default OK to use TV coax for microphone?

In message , Jeff Liebermann
writes
On Sat, 03 May 2008 21:23:08 -0400, "Michael A. Terrell"
wrote:

Use a magnet, and see for yourself. The copper plating smears
when cut with dykes, and makes the coated steel appear to be solid
copper.


Trivia:
Dike = Diagonal Cutters
http://en.wikipedia.org/wiki/Diagonal_pliers
Dyke = Lesbian
http://en.wikipedia.org/wiki/Dyke_(lesbian)
Dyke or Dike = Earthen wall or dam
http://en.wikipedia.org/wiki/Dike_%28construction%29

Methinks "dikes" would be the correct spelling.


In the NE of England, 'dyke' also = 'ditch'.
From Wiktionary:
Dike or dyke (construction), either a long wall or bank built to keep
out the sea or enclose or separate land, or the ditch from which the
material was dug, or the combination of the two.

Apologies for the digression....
--
Ian
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Default OK to use TV coax for microphone?

On Sun, 04 May 2008 08:13:12 +0100, don pearce wrote:


Phil Allison wrote:
"Richard Crowley"
(1) Is it ok to use this sort of coax for a microphone?
Not enough details to answer your question adequately. First of all,
the kinds of microphones used for audio applications (reinforcement,
recording, etc.) are usually balanced and require cable with two inner
wires and an outside shield/screen. If you are trying to use a
balanced mic, then the cable is unsuitable because it is unbalanced.



** Not true at all !!

There is NO reason not to use a (suitable) co-axial type cable with a
microphone - either low or high impedance.

Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables.

Try it out if you don't believe this.


Of course a proper microphone cable is SCREENED balanced twisted pair, so
it enjoys the multiple benefits of electric screening by the outer, the
common mode nature of any residual interference and magnetic interference
cancellation by the twist in the balanced pair. A poorly screened coax
cable such as TV coax has only a part of the first of those so this claim
is clearly nonsensical. If it were true, professional microphone and mixer
companies would not be going to the trouble of designing balanced kit.



The length I need to use is 3 to 4 metres.
Not really important to the question. It wouldn't make much difference
if it were 1 m or 1Km



** If the mic is high impedance ( ie 50 kohms), then more than 10
metres or so of cable will cause high frequency response peaking and
early roll off as the cable capacitance loads the transformer inside the
mic.



If the mic is low impedance ( ie circa 250 ohms), then hundreds of
metres can be used - but not kilometres.



This is true.

d


Good quality coax will do the job if you don't mind the impedance mismatch
and if you want balanced line then you could use a pair of coax feeds in
parallel (impedance about 100 ohms for rg58). Also there's coax and
there's coax, I've seen rg58 like TV down-lead and others like shrunk down
UR67M.


--
___ _______ ___ ___ ___ __ ____
/ _ \/ __/ _ | / _ \ / _ \/ _ |/ / / / /
/ // / _// __ |/ // / / ___/ __ / /_/ / /__
/____/___/_/ |_/____/ /_/ /_/ |_\____/____/

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Default OK to use TV coax for microphone?

On Sun, 04 May 2008 10:30:53 +0100, Dead Paul
wrote:

On Sun, 04 May 2008 08:13:12 +0100, don pearce wrote:


Phil Allison wrote:
"Richard Crowley"
(1) Is it ok to use this sort of coax for a microphone?
Not enough details to answer your question adequately. First of all,
the kinds of microphones used for audio applications (reinforcement,
recording, etc.) are usually balanced and require cable with two inner
wires and an outside shield/screen. If you are trying to use a
balanced mic, then the cable is unsuitable because it is unbalanced.


** Not true at all !!

There is NO reason not to use a (suitable) co-axial type cable with a
microphone - either low or high impedance.

Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables.

Try it out if you don't believe this.


Of course a proper microphone cable is SCREENED balanced twisted pair, so
it enjoys the multiple benefits of electric screening by the outer, the
common mode nature of any residual interference and magnetic interference
cancellation by the twist in the balanced pair. A poorly screened coax
cable such as TV coax has only a part of the first of those so this claim
is clearly nonsensical. If it were true, professional microphone and mixer
companies would not be going to the trouble of designing balanced kit.



The length I need to use is 3 to 4 metres.
Not really important to the question. It wouldn't make much difference
if it were 1 m or 1Km


** If the mic is high impedance ( ie 50 kohms), then more than 10
metres or so of cable will cause high frequency response peaking and
early roll off as the cable capacitance loads the transformer inside the
mic.



If the mic is low impedance ( ie circa 250 ohms), then hundreds of
metres can be used - but not kilometres.



This is true.

d


Good quality coax will do the job if you don't mind the impedance mismatch
and if you want balanced line then you could use a pair of coax feeds in
parallel (impedance about 100 ohms for rg58). Also there's coax and
there's coax, I've seen rg58 like TV down-lead and others like shrunk down
UR67M.


A pair of coaxes in parallel is balanced, but you miss out on the
close proximity and twist. The first makes the magnetic loop very
small, while the second causes the polarity of any residual pickup to
swap every inch or so, giving a net cancellation.

As I said in my first reply, if I was forced to use coax for a
microphone, domestic TV grade would be a very poor choice because in
general it has perhaps no more than 10% screening (just enough in fact
to give the cable a stable characteristic impedance, but no more).
Microphone signals are too small to mess around this way. Decent audio
grade cable has screening approaching 100%.

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


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Default OK to use TV coax for microphone?

On Sat 03 May 2008 11:10:02, Don Pearce wrote:

On Sat, 03 May 2008 10:58:27 +0100, Chris Siz
wrote:

I am in the UK and have a 10m length of some cheap TV aerial coax.
It came from a discount store as a TV coax extension cable. I
measure the cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't
want an impaired audio signal. The length I need to use is 3 to 4
metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax and
prone to interference or mess up the aerial signal?


If you can get hold of some better cable do so. You have two
problems here - first coax isn't balanced, which is sort of bad
news for tiny signals such as you get from a mic. And secondly, to
compound that, if you strip back a little of the outer sheath, you
will find that the screen is 90% holes - in other words, the cable
is just about unscreened.


Um, yes. It is exactly like that. I had thought maybe they were using
very thin wires and that way getting a reasonable amount of physcial
screening but the wires I found were so sparse that it must be more
like what you describe!

As for using it for UHF TV, go ahead - that is what it is meant
for, and 10 meters is just about the maximum run length before you
need to think about using something better.

d


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Default OK to use TV coax for microphone?


"Ian Thompson-Bell" wrote in message
...
No they expect to see 1K2 to 2K not 10K and that is what most pro mic pres
provide. 10K input impedance is for bridging line levels.

Cheers

Ian


Er, not in every case. In any case my point about the mic being regarded as
a voltage source remains true.

For speech use (3K) you can get away with just about anything!

Les.


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Default OK to use TV coax for microphone?

On Sat 03 May 2008 15:54:24, wrote:

On May 3, 4:58 am, Chris Siz wrote:
I am in the UK and have a 10m length of some cheap TV aerial
coax. It came from a discount store as a TV coax extension
cable. I measure the cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't
want an impaired audio signal. The length I need to use is 3 to
4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax
and prone to interference or mess up the aerial signal?

--

[x-posted to 3 relevant groups]


Isn't coax kind of rigid? Will the microphone need to move around?


This cheapo coax is quite flexible. It may an indication of poor
physical resistance to squashing and also of limited copper content.
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Default OK to use TV coax for microphone?

On Sat 03 May 2008 19:05:41, Kevin McMurtrie wrote:

In article ,
Chris Siz wrote:

I am in the UK and have a 10m length of some cheap TV aerial
coax. It came from a discount store as a TV coax extension
cable. I measure the cable diameter as 4.8mm.

(1) Is it ok to use this sort of coax for a microphone? I don't
want an impaired audio signal. The length I need to use is 3 to
4 metres.

(2) Is it ok for UHF TV or is it actually quite low grade coax
and prone to interference or mess up the aerial signal?


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.


I am the OP and as you can probably tell I am no electronics or
radio expert. However even my limited knowledge struggles to
believe some of the points you have made.

Forgive me if it's more obvious to others but your's is not some
sort of funny posting is it?
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Default OK to use TV coax for microphone?

On Sun 04 May 2008 04:28:55, Jeff Liebermann wrote:

Incidentally, I blundered across this data sheet for RG-6/u. They
can make it just about any way you want it, and still call it
RG-6/u. Note the line with:
6) Braiding coverage: Between 30 - 97% available;
I can't imagine who would want to buy 30% coverage outer
shielding.
http://www.tootoo.com/supplier/produ...9/RG6%252fU.ht
ml



I too have started to feeling that there is a heck of lot more
variation than I realised in how coax cables can be made and yet are
still conform to some particular technical specification.

I came across some interesting articles at "abc cables". Here are some
which caught my eye. http://www.abccables.com/technical-support.html

Wire? or Cable?
RG6 Copper vs. Copper Clad Steel
RG59 vs. RG6
Better Copper?

I would like to get other (supplier's) info as that site is quite
useful. Has anyone got any links to these sort of explanatory
articles?


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On Sun 04 May 2008 02:23:08, Michael A. Terrell wrote:


Walt Davidson wrote:

On Sat, 03 May 2008 11:05:41 -0700, Kevin McMurtrie
wrote:

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.


What planet do you live on? I have never seen TV coax as you
describe. Coax with copper-plated steel inner conductor is
mostly used as data cable (ethernet).



Then you've never seen the wire used by cable TV and Satellite TV
companies. Pure copper is too expensive these days, and too soft
for repeated flexing. If you want to pay over a dollar a foot for
copper core TV coax, go ahead. The last time I had to buy some it
was about eight times the price of the foil shield W/braid TV
coax, and useless for UHF. Use a magnet, and see for yourself.
The copper plating smears when cut with dykes, and makes the
coated steel appear to be solid copper.


If copper is soft then wouldn't that make it good for repeated
flexing in the sense that copper isn't so stiff that it wouldn't
split or crack?
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On Sat 03 May 2008 22:24:49, Dead Paul wrote:

On Sat, 03 May 2008 19:39:45 +0100, Walt Davidson wrote:

On Sat, 03 May 2008 11:05:41 -0700, Kevin McMurtrie
wrote:

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.


What planet do you live on? I have never seen TV coax as you
describe. Coax with copper-plated steel inner conductor is mostly
used as data cable (ethernet).


You want to see the crap which passes for rg58 at maplin
electronics.



Maplins selling crap merchandise doesn't surprise me. (Though to be
fair, it does sell the odd good item too.)

But where would I go to get half-decent cables in relatively short
lengths (not 50m drums) without paying a fortune for ultra quality
dedicated-hobbyist stuff or exhorbitant delivery charges?
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On Sun, 04 May 2008 09:37:50 +0000, Don Pearce wrote:

On Sun, 04 May 2008 10:30:53 +0100, Dead Paul wrote:

On Sun, 04 May 2008 08:13:12 +0100, don pearce wrote:


Phil Allison wrote:
"Richard Crowley"
(1) Is it ok to use this sort of coax for a microphone?
Not enough details to answer your question adequately. First of all,
the kinds of microphones used for audio applications (reinforcement,
recording, etc.) are usually balanced and require cable with two
inner wires and an outside shield/screen. If you are trying to use a
balanced mic, then the cable is unsuitable because it is unbalanced.


** Not true at all !!

There is NO reason not to use a (suitable) co-axial type cable with a
microphone - either low or high impedance.

Despite all the nonsense you WILL have read elsewhere, co-axial
cables have as good or better rejection of external hum and noise
sources as do balanced twin wire cables.

Try it out if you don't believe this.


Of course a proper microphone cable is SCREENED balanced twisted pair,
so it enjoys the multiple benefits of electric screening by the outer,
the common mode nature of any residual interference and magnetic
interference cancellation by the twist in the balanced pair. A poorly
screened coax cable such as TV coax has only a part of the first of
those so this claim is clearly nonsensical. If it were true,
professional microphone and mixer companies would not be going to the
trouble of designing balanced kit.



The length I need to use is 3 to 4 metres.
Not really important to the question. It wouldn't make much
difference if it were 1 m or 1Km


** If the mic is high impedance ( ie 50 kohms), then more than 10
metres or so of cable will cause high frequency response peaking and
early roll off as the cable capacitance loads the transformer inside
the mic.



If the mic is low impedance ( ie circa 250 ohms), then hundreds of
metres can be used - but not kilometres.



This is true.

d


Good quality coax will do the job if you don't mind the impedance
mismatch and if you want balanced line then you could use a pair of coax
feeds in parallel (impedance about 100 ohms for rg58). Also there's coax
and there's coax, I've seen rg58 like TV down-lead and others like shrunk
down UR67M.


A pair of coaxes in parallel is balanced, but you miss out on the close
proximity and twist. The first makes the magnetic loop very small,



yeah but there is no "mag loop" outside of the shield with coax.

while
the second causes the polarity of any residual pickup to swap every inch
or so, giving a net cancellation.


no pickup inside coax.

As I said in my first reply, if I was forced to use coax for a microphone,
domestic TV grade would be a very poor choice because in general it has
perhaps no more than 10% screening (just enough in fact to give the cable
a stable characteristic impedance, but no more). Microphone signals are
too small to mess around this way. Decent audio grade cable has screening
approaching 100%.


fully agree.


d


--
___ _______ ___ ___ ___ __ ____
/ _ \/ __/ _ | / _ \ / _ \/ _ |/ / / / /
/ // / _// __ |/ // / / ___/ __ / /_/ / /__
/____/___/_/ |_/____/ /_/ /_/ |_\____/____/

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"don pearce PITA smug ****** "

"Richard Crowley Arse Licker "

If you are trying to use a balanced
mic, then the cable is unsuitable because it is unbalanced.



** Not true at all !!

There is NO reason not to use a (suitable) co-axial type cable with a
microphone - either low or high impedance.

Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables.

Try it out if you don't believe this.


Of course a proper microphone cable is SCREENED balanced twisted pair,



** Exactly what I was referring to above.

Mic cable IS a balanced twin wire cable.


A poorly screened coax cable such as TV coax has only a part of the first
of those



** It ain't necessarily poorly screened and it ain't necessarily what I just
posted about.

Do learn to read sometime - ****wit.


has only a part of the first of those ..



** Not true of co-axial cable in general.

Do learn to read sometime - ****wit.


so this claim is clearly nonsensical.

** Not at all -

your irrelevant & asinine claims are nonsensical

- ****wit.


If it were true, professional microphone and mixer companies would not be
going to the trouble of designing balanced kit.



** More completely irrelevant nonsense.


" Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables. Try it out if you don't believe this. "

Obviously YOU need to do this too - ****wit.

Since you are so PIG ignorant of the basic physics of co-axial cable.




....... Phil




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Default OK to use TV coax for microphone?


Phil Allison wrote:
"don pearce PITA smug ****** "
"Richard Crowley Arse Licker "
If you are trying to use a balanced
mic, then the cable is unsuitable because it is unbalanced.

** Not true at all !!

There is NO reason not to use a (suitable) co-axial type cable with a
microphone - either low or high impedance.

Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables.

Try it out if you don't believe this.

Of course a proper microphone cable is SCREENED balanced twisted pair,



** Exactly what I was referring to above.

Mic cable IS a balanced twin wire cable.


Having trouble spotting the capital letters, are you? (yes, I saw yours,
and that is what prompted this question, the relevance obviously passed
you by).


A poorly screened coax cable such as TV coax has only a part of the first
of those



** It ain't necessarily poorly screened and it ain't necessarily what I just
posted about.

Do learn to read sometime - ****wit.


we know exactly what this cable is - and yes it is poorly screened. Do
try to follow the threads. And if you want to post about something else,
start a new thread.


has only a part of the first of those ..



** Not true of co-axial cable in general.

Do learn to read sometime - ****wit.


so this claim is clearly nonsensical.

** Not at all -

your irrelevant & asinine claims are nonsensical

- ****wit.


If it were true, professional microphone and mixer companies would not be
going to the trouble of designing balanced kit.



** More completely irrelevant nonsense.


Irrelevant is it? Tell that to Neve, Neumann, Shure, Sennheiser, Leevers
Rich - need I go on?


" Despite all the nonsense you WILL have read elsewhere, co-axial cables
have as good or better rejection of external hum and noise sources as do
balanced twin wire cables. Try it out if you don't believe this. "

Obviously YOU need to do this too - ****wit.

Since you are so PIG ignorant of the basic physics of co-axial cable.


I appear to have a vastly better grasp of the topic than you, not
surprising really when you consider that I have designed ultra low noise
microwave measuring equipment.

d
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