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rf sheilding

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Anonymous
November 10, 2004 1:11:40 AM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

hi to all,
my recording studio is located close to a college ratio station
antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
getting into my studio gear, what can i do to shield the equipment
from that stray rf?

More about : sheilding

Anonymous
November 10, 2004 2:11:17 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

"g subs" <stylzmovements2000@yahoo.com> wrote in message
news:51eca3ef.0411092211.169885d1@posting.google.com...
> hi to all,
> my recording studio is located close to a college ratio station
> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> getting into my studio gear, what can i do to shield the equipment
> from that stray rf?

I'm trying to remember what we did a long time ago in a similar situation. I
think it involved running some very heavy ground wires to some copper strips
several inches wide under all the gear and grounding everything very
carefully. One of the problems with today's gear I imagine is they don't use
the same kind of heavy duty xformers that were in mixers 20+ years ago. Does
the RF get into all the gear or just some of it? Maybe just the racks need
better shielding and grounding.

--
McWebber
No email replies read
If someone tells you to forward an email to all your friends
please forget that I'm your friend.
Anonymous
November 10, 2004 2:52:00 PM

Archived from groups: rec.audio.pro (More info?)

In article <51eca3ef.0411092211.169885d1@posting.google.com> stylzmovements2000@yahoo.com writes:

> my recording studio is located close to a college ratio station
> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> getting into my studio gear, what can i do to shield the equipment
> from that stray rf?

Move.

If thta's too difficult, replace all your wiring with good quality
shielded cable, balanced in and out all the way, replacing any
unbalanced gear with an equivalent with balanced inputs and outputs.

If that's too difficult, move.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Related resources
Anonymous
November 10, 2004 3:07:32 PM

Archived from groups: rec.audio.pro (More info?)

In article <znr1100093813k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
>
>In article <51eca3ef.0411092211.169885d1@posting.google.com> stylzmovements2000@yahoo.com writes:
>
>> my recording studio is located close to a college ratio station
>> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
>> getting into my studio gear, what can i do to shield the equipment
>> from that stray rf?
>
>Move.
>
>If thta's too difficult, replace all your wiring with good quality
>shielded cable, balanced in and out all the way, replacing any
>unbalanced gear with an equivalent with balanced inputs and outputs.

AND a well-engineered grounding system, rather than an ad-hoc mess of
cables with grounds duplicated all over the place.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
November 10, 2004 3:07:33 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:cmthsk$92d$1@panix2.panix.com...
> In article <znr1100093813k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
>>
>>In article <51eca3ef.0411092211.169885d1@posting.google.com>
>>stylzmovements2000@yahoo.com writes:
>>
>>> my recording studio is located close to a college ratio station
>>> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
>>> getting into my studio gear, what can i do to shield the equipment
>>> from that stray rf?
>>
>>Move.
>>
>>If thta's too difficult, replace all your wiring with good quality
>>shielded cable, balanced in and out all the way, replacing any
>>unbalanced gear with an equivalent with balanced inputs and outputs.
>
> AND a well-engineered grounding system, rather than an ad-hoc mess of
> cables with grounds duplicated all over the place.
> --scott
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

All of the advice you have received, all appropriate, shows how difficult it
sometimes is to cure the effects of strong rf fields in audio equipment. I
once installed two early Tascam mixers for Encyclopedia Brittanica, one on
the second floor of a downtown Chicago building and one on the fourth floor.
Sure, the mixer was not top drawer equipment, but it was appropriate for the
narration recording they did at that time. The one on the fourth floor was
perfectly clean. Just plugged everything in and began working. The one on
the second floor was rife with rf... on every mic channel. We swapped the
two mixers. Nothing changed. The clean mixer became the dirty mixer. The
interference was inconsistent. Move faders or EQ controls and the stations
received might change... or might not. We did all the grounding things
mentioned in earlier posts... 4 inch wide copper strap down the elevator
shaft brazed to main water lines. Tied in everything to that: short runs,
solid connections. Everything. Even called in electricians to re-do much
of the wiring that fed that 'control-room', paying particular attention to
bonding the ground leads in and through junction boxes. Installing R/C
networks on the inputs of each channel module made the most difference.
Finally gave up. They moved the studio to another space on the fourth
floor, where no RF difficulties were experienced. Good luck.

Steve King
Anonymous
November 10, 2004 3:45:51 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

You might also have some luck with simple low pass filtration although this
will involve some soldering. The audio cables' hot lead (center wire) can be
soldered to the simplest coil, such as a toroid coil from an old motherboard
.. the other side of the coil is then run to the plug to the equipment.Then a
very small capacitor, such as 470 pf, taken to ground immediately after the
coil.
The coil blocks the RF and the cap grounds any residual signal on the lines.
Basically, the RF, of whatever frequency, is being rectified in your audio
gear.


"McWebber" <mcwebber@my-deja.com> wrote in message
news:sP6dnTIKS5-bow_cRVn-rg@comcast.com...
> "g subs" <stylzmovements2000@yahoo.com> wrote in message
> news:51eca3ef.0411092211.169885d1@posting.google.com...
> > hi to all,
> > my recording studio is located close to a college ratio station
> > antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> > getting into my studio gear, what can i do to shield the equipment
> > from that stray rf?
>
> I'm trying to remember what we did a long time ago in a similar situation.
I
> think it involved running some very heavy ground wires to some copper
strips
> several inches wide under all the gear and grounding everything very
> carefully. One of the problems with today's gear I imagine is they don't
use
> the same kind of heavy duty xformers that were in mixers 20+ years ago.
Does
> the RF get into all the gear or just some of it? Maybe just the racks need
> better shielding and grounding.
>
> --
> McWebber
> No email replies read
> If someone tells you to forward an email to all your friends
> please forget that I'm your friend.
>
>
Anonymous
November 10, 2004 6:14:17 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

g subs wrote:
> hi to all,
> my recording studio is located close to a college ratio station
> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> getting into my studio gear, what can i do to shield the equipment
> from that stray rf?

There is a long discussion ongoing on this question right
now on the pro-audio mailing list:

==For info on Pro-Audio, send 'info pro-audio' to
majordomo@pgm.com ===

This is an excellent list for discussion of matters relating
to cabling and shielding. It is moderated.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Anonymous
November 10, 2004 8:17:17 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

"g subs"
>
> hi to all,
> my recording studio is located close to a college ratio station
> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> getting into my studio gear, what can i do to shield the equipment
> from that stray rf?



** Either install full Faraday shielding of the studio rooms or move
house.




............ Phil
November 10, 2004 8:17:18 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

> >
> > hi to all,
> > my recording studio is located close to a college ratio station
> > antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> > getting into my studio gear, what can i do to shield the equipment
> > from that stray rf?
>
>
I'll assume it's an FM station and that you are getting various kinds
of hum with maybe a little modulation in there as you move or touch
cables.

The best way is to install small series resistors at the inputs to
your gear but this requires soldering etc.

You may have some luck with clamp on ferrite filterers that can be
clamped over the outside of cable.

Usually the entry point is via audio and power cable. Unless the RF
is very very strong, entry directly into the gear via the chassis in
usually not a problem.

Disconnnect your cables and connect them one at a time to try to
isolate the problem to particular cable.

Try to wire the shield pin of XLR cable directly to the chassis, maybe
try some copper tape on the outsire of the XLR conector directly to
the chassis.

Generally at VHF, ground wires rods etc will not help.
Anonymous
November 10, 2004 11:06:58 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

John O wrote:

>>my recording studio is located close to a college ratio station
>>antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
>>getting into my studio gear, what can i do to shield the equipment
>>from that stray rf?

> Assuming you can't move, and assuming that enclosing your studio in a
> Faraday cage would result in the same looks you get when you wear your foil
> hat, there are some things.

I'm going to ask a question that I might not be asking if I understood
more about electronics: is there any reason why you need to enclose
the entire room? I know a Faraday cage is sufficient, but is it really
necessary? Since you know the exact direction the radiation is coming
from, what if you (say) put up a well-grounded wire mesh in a plane
perpendicular to the line from the studio to the radio station's antenna
such that the mesh casts a "shadow" that covers the entire studio?
Or maybe it doesn't even need to be in that plane as long as it casts
the proper shadow.

Am I way off track, or is there actually some benefit to this?

If that doesn't work, how hard is it, really to put up a Faraday
cage around the studio? Seems like you could put a layer of
chicken wire on the walls, ceiling, and floor, connect it all to
itself electrically, then cover the walls and ceiling with another
layer of sheetrock. The floor might be a little tougher, but not
too hard if it's already carpeted (just put the chicken wire under
the carpet pad, then replace carpet and pad). Of course, how
feasible this is depends on whether you just use one room for
the studio or use the whole house occasionally like a former
roommate[1] of mine did (drums in the living room, etc., etc.).

- Logan

[1] Hey Ross, if you're out there, hope you're doing well!
Anonymous
November 10, 2004 11:06:59 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

Logan Shaw <lshaw-usenet@austin.rr.com> wrote:
>
>I'm going to ask a question that I might not be asking if I understood
>more about electronics: is there any reason why you need to enclose
>the entire room? I know a Faraday cage is sufficient, but is it really
>necessary? Since you know the exact direction the radiation is coming
>from, what if you (say) put up a well-grounded wire mesh in a plane
>perpendicular to the line from the studio to the radio station's antenna
>such that the mesh casts a "shadow" that covers the entire studio?
>Or maybe it doesn't even need to be in that plane as long as it casts
>the proper shadow.

It does not come from just one direction. It reflects off of other
objects and bounces back from several directions. A large plane shield
will work, but it has to be many times the size of a wavelength.

In fact, your gear already SHOULD have a Faraday shield around everything.
It should have electronics in metal boxes, with shields around all of
the cabling, and no gaps in the coverage anywhere.

The problem is when manufacturers skimp on shielding, when they build
controls that leave open holes in cabinets or when they use plastic cabinets
without metal shielding inside.

The problem is when there are ground loops, causing circulating currents in
the shield lines that are there to protect you, and making them do more harm
than good. Some of them are inside the cases, even!

The problem is when connectors aren't built properly, so that when XLR cables
are strung together the shields over the connection are either floating or
are both tied to ground so as to form a ground loop.

>If that doesn't work, how hard is it, really to put up a Faraday
>cage around the studio? Seems like you could put a layer of
>chicken wire on the walls, ceiling, and floor, connect it all to
>itself electrically, then cover the walls and ceiling with another
>layer of sheetrock. The floor might be a little tougher, but not
>too hard if it's already carpeted (just put the chicken wire under
>the carpet pad, then replace carpet and pad). Of course, how
>feasible this is depends on whether you just use one room for
>the studio or use the whole house occasionally like a former
>roommate[1] of mine did (drums in the living room, etc., etc.).

Chicken wire isn't very conductive. Copper mesh is okay, and it's a good idea
that the mesh squares be smaller than a 20th of the wavelength of interest
or so. The real problem is sealing around doors and windows. IEC makes some
nice shielded rooms that are good for guitar amps and other applications
where it's basically impossible to shield the equipment properly.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
November 10, 2004 11:42:00 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

> hi to all,
> my recording studio is located close to a college ratio station
> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> getting into my studio gear, what can i do to shield the equipment
> from that stray rf?

The same thing they are doing to keep it from getting into their
equipment which is even closer to the antenna than you are.

If you call and request that the engineer of that station call you back
because of this problem, you will most likely get a friendly call back
with some great suggestions, perhaps even a trip to your place to try
and help you out.

Usually, the problem is using cheap consumer gear, or stuff with phono
or RCA plugs rather than XLR so you don't have any ground loop problems.
November 10, 2004 11:47:06 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

> I'm going to ask a question that I might not be asking if I understood
> more about electronics: is there any reason why you need to enclose
> the entire room?

No. Just a quick easy way out rather than finding the problem and solving it
where it is at.
Making the room a faraday cage will cause other problems, like you never being
able to use wireless mics, radios or tvs that you might want to receive and
record.

> I know a Faraday cage is sufficient, but is it really
> necessary?

I am sure the studio of the station next to you doesn't do that, and they are
closer to the antenna than you are, so no.

> If that doesn't work, how hard is it, really to put up a Faraday
> cage around the studio?

A lot harder than just finding the problem and fixing it which will be a LOT
easier to fix than constructing the entire room into a Faraday cage. In fact,
if the problem is from ground loops, you are still going to have other problems
like hum anyway, even with the Faraday cage.

> Seems like you could put a layer of
> chicken wire on the walls, ceiling, and floor, connect it all to
> itself electrically, then cover the walls and ceiling with another
> layer of sheetrock.

Why not just move the building a few miles away if you are willing to go a
complicated route?
November 10, 2004 11:48:59 PM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

> The problem is when there are ground loops, causing circulating currents in
> the shield lines that are there to protect you, and making them do more harm
> than good. Some of them are inside the cases, even!
>
> The problem is when connectors aren't built properly, so that when XLR cables
> are strung together the shields over the connection are either floating or
> are both tied to ground so as to form a ground loop.

Yes, this is going to be where the problem is. If you have RCA connectors or
two conductor phono plugs, you are screwed. You will need to buy pro gear in
that case and get rid of the consumer stuff.
Anonymous
November 11, 2004 3:41:10 AM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

Truth wrote:
>> Seems like you could put a layer of
>>chicken wire on the walls, ceiling, and floor, connect it all to
>>itself electrically, then cover the walls and ceiling with another
>>layer of sheetrock.

> Why not just move the building a few miles away if you are willing to go a
> complicated route?

It is complicated, but it's not THAT complicated. Besides, the faraday
cage project could be combined with a soundproofing project, so it could
have double benefit. I admit, though, that the door issue seems
problematic. I was going to suggest a metal door with metal frame
(and copper contacts added all around the perimeter of the door so that
it connects to the frame), but metal doors seem to be all made of steel,
which isn't a great conductor.

- Logan
Anonymous
November 11, 2004 3:49:35 AM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

Truth wrote:

>>what can i do to shield the equipment
>>from that stray rf?

> The same thing they are doing to keep it from getting into their
> equipment which is even closer to the antenna than you are.
>
> If you call and request that the engineer of that station call you back
> because of this problem, you will most likely get a friendly call back
> with some great suggestions,

While I appreciate the fact that badly set up (or poorly chosen)
equipment could be a major factor, what about other equipment that
the studio doesn't have any control over? Just last weekend, I
was doing (live) sound for a band, and when the bass player plugged
his bass into the bass amp and turned it on, the lead guitarist said,
"Why is the radio coming out of the bass cabinet?" Probably the
answer is that the venue is located not far from the one hill in
town where a whole bunch of radio transmitters are located. More
to the point, as the sound guy, I don't control the bass guitar
and the bass cabinet. Yes, maybe I have some influence, but it's
nice to avoid situations where you have to become a problem-solver
for someone else's equipment.

On the other hand, maybe it's not so nice that it merits rebuilding
an entire room of the house to add the faraday cage...

- Logan
Anonymous
November 11, 2004 4:09:02 AM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

easy, put a second skin inside and put chicken wire behind it.
works a treat.when used with a couple of car body earthing straps.
as for the walls, we found that using the thick silver foil type underfloor
lay u can get from builders stores for insulation perfect
very cheap as well.

mike uk

"Logan Shaw" <lshaw-usenet@austin.rr.com> wrote in message
news:Gyykd.1964$2v2.1839@fe1.texas.rr.com...
> Truth wrote:
> >> Seems like you could put a layer of
> >>chicken wire on the walls, ceiling, and floor, connect it all to
> >>itself electrically, then cover the walls and ceiling with another
> >>layer of sheetrock.
>
> > Why not just move the building a few miles away if you are willing to go
a
> > complicated route?
>
> It is complicated, but it's not THAT complicated. Besides, the faraday
> cage project could be combined with a soundproofing project, so it could
> have double benefit. I admit, though, that the door issue seems
> problematic. I was going to suggest a metal door with metal frame
> (and copper contacts added all around the perimeter of the door so that
> it connects to the frame), but metal doors seem to be all made of steel,
> which isn't a great conductor.
>
> - Logan


---
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Checked by AVG anti-virus system (http://www.grisoft.com).
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Anonymous
November 11, 2004 6:21:00 AM

Archived from groups: alt.radio.broadcasting,alt.radio.pirate,rec.audio.pro (More info?)

g subs wrote:

> hi to all,
> my recording studio is located close to a college ratio station
> antenna , they radiate 18,000 watts 24 hrs a day , the radiation is
> getting into my studio gear, what can i do to shield the equipment
> from that stray rf?

You don't say what kind of station it is, AM or FM. If you are near an AM
station, your problems are more likely to be power and telephone lines
bringing in rf as antennas, and can be best helped there, at least to start
with. All the suggestions about massive grounding and separating signal
ground from shield ground are also on the right track. You might also find
a local ham to help. They live in these fields all the time. Also, if it is
FM, a two meter handy talky up close could deliver a larger test field than
you are likely to get from the station.
!