[Scott Dorsey]

Eeyore wrote:
Paul Stamler wrote:

"Scott Dorsey" wrote in message

It is a known problem with all microphones, however I did not have any
problem when I reviewed these mikes. I keyed a 1W handie-talkie on 146 MHz
up
within a few inches of the mike (which is my regular RF test).

AM or FM ?

No modulation. (The HT is actually FM modulated, but usually just a blast
of A0 shows up problems).

This test is how I first discovered the pin 1-shield disconnect on Neumann
microphones.

Yes, but what happens (or doesn't happen) at 146MHz could be very different
from what happens at 790kHz.

Absolutely ! And that band is IME the one which typically causes all the
trouble.

Mostly because it's got lots of high powered stuff with AM modulation on it.
And AM is very easily detected with a simple diode. I have had FM signals
leak into audio before just due to slope-detection, but it takes a whole
lot more of it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Eeyore wrote:

I saw it implied that as a result the cable has an unbalanced signal on it
though which must introduce a whole new set of problems.

It does, but it's a very low-Z unbalanced signal that is going into a
transformer in the preamp that acts as an effective low-pass. It's got
ferrite slugs on either end. So it might be a problem in very high RF
environments but normally isn't a big deal.

I believe that the solid state version of the 122 has the output transformer
built into the microphone to avoid just this problem.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Truth]

On Sep 13, 2:23 pm, Mark wrote:
On Sep 13, 1:14 pm, "Paul Stamler" wrote:



"Truth" wrote in message

roups.com...

The cable connecting the ribbon mic to it's dedicated power supply is
a 7 pin cable provided by Royer Labs. Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

Much more likely in the mic itself. The transformer in the power supply is
usually pretty good at filtering out RF on the line.

Peace,
Paul

I'm gonna guess at this point that the mics power supply has a
switching power supply in there and that the switching freq or
harmonic thereof is beating with the 790 kHz AM station. If you turn
off the mics and the power supplies do you still hear the squeal in
the AM radio on 790?

If you turn off all your audio equipment do you still hear the squeal
in the AM radio?

Does the squeal ever change pitch?

If so what makes it change pitch?

How far away from you is the 790 kHz AM radio stations antennas?

Mark

Mark

Yes, If I turn off the equipment, the radio still squeals and vice
versa, if I turn off the radios in the house the equipment still
squeals. The squeal changes pitch though it stays high pitched. It's
the same type of squeal you get when you turn the dial between
stations. Just a badly received signal I suspect. It's always
changing, coming and going and moving about. I don't know why the
squeal exists in the first place that is something I want to learn
more about. The problem only occurs when the station is squealing. I
only found out yesterday that this was a RF problem so I haven't had
the chance to do much testing or research into yet. If the problem is
related to the radio station as I suspect now, then I will call them
and let them know.

I checked the radio this morning, no squeal. I turned the equipment
on and tested with both preamps, no squeal. They coincide. Last
night when I was hearing the squeal the equipment was also squealing.
The squeal from a badly received station and the sound I'm hearing
when the equipment acts up are very similar if not identical, like a
modified version of it. Why the squeal without the content such as
voice or music I wonder though? I was only able to hear the content
very faintly beneath all the squeal. Usually I can't hear the content
just the squeal.

[Truth]

On Sep 13, 1:32 pm, (Scott Dorsey) wrote:
Truth wrote:
The cable connecting the ribbon mic to it's dedicated power supply is
a 7 pin cable provided by Royer Labs. Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

If it's an RF problem, it has nothing to do with the power system.

I'm not so sure it _is_ an RF problem, though.

When you heard this squealing sound on an AM radio tuned to 790, was
your audio gear operating at the time?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

The squeal is there on the radio without my equipment being on and
vice versa. I just turned on the station now and I'm hearing some
squeal again tonight though none in the equipment thankfully. The
only that's changed is I located the power supplies out in the hall
now along and extended the 7 pin mic cables so they are laid out at
almost full length in a straight path rather than piled in a random
heap on the floor. Perhaps it was the cable all along? It's too
early to tell though, every time I think the problem has gone, it
comes back eventually, so I will keep a watch out for it and conduct
some more tests when it comes back.

[Truth]

On Sep 13, 1:28 pm, (Scott Dorsey) wrote:
Truth wrote:
House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics

OKAY! So you don't have normal ribbon microphones at all. You have
the 122V.

So, the first question: Do you hear the problem with the 122V turned off?
If turning off the mike stops the noise, the rectification is taking place
inside the mike.

The second question: If you connect up only a single microphone, do you
hear it?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Yes, turning off the mic stops the noise from what I remember. That
still leaves the power box, or 7 pin cables connecting the box to the
mic as possible sources if you disregard the power itself. Well, the
source in my opinion is the radio station but there is little I can do
about that. After moving the power boxes out in the hall and
unwinding the 7 pin cables out so they are more or less straight and
not a in pile, the problem has seemed to disappear. It's too early to
say though. Every time I think I got rid of it, it comes back
eventually. This makes me think the cable is the problem and I would
benefit from a shorter run. It's something I will mention to Royer
when I contact them. I'm monitoring using the Pendulum preamp as I
type this, all is good right now.

I notice it with both microphones, sometimes at the same time,
sometimes at different times, whether they are both powered or not.
If I turn off one I still hear it in the other.

[Truth]

On Sep 13, 2:48 pm, Eeyore
wrote:
Scott Dorsey wrote:
Eeyore wrote:
Scott Dorsey wrote:
Eeyore wrote:
Scott Dorsey wrote:
AndyP wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always. There are some poorly-designed transformer inputs out
there too, though.

What kind of preamp, microphone, and cable are we dealing with here?
And what makes you think it's AM?

He said it was an AM station.

Right, but he said he was hearing a whistle.

AM is also readily demodulated by any diode-like behaviour.

Yes, but then you hear voices.

You got me there. Joke ?

No, when AM radio is demodulated in an audio chain, you can hear the
modulation of the AM signal, which is usually music or an announcer.

I thought he said he did hear that (and also the heterodynes or whatever) ?

Graham

Usually I just hear the squeal and no content. Yesterday was the first
time I could hear the content as well, though it was very faint and
muffled compared to the very present squeal.

[Truth]

On Sep 13, 4:12 pm, Mike Rivers wrote:
On Sep 13, 1:03 pm, Truth wrote:

That's the thing, I don't know what is the problem yet. It could be
the house lines acting as antenna and not the equipment itself which
is at fault.

Well you have to stop guessing and start doing some troubleshooting.
Start disconnecting things from the microphone back to the computer,
one at a time, until the interference goes away. And start by turning
off the radio.

I've been doing that kind of troubleshooting and it comes down to the
Royer equipment and the 790 AM radio station. Last night both the
radios and the equipment were squealing. Turning off the radios had
no effect on the squeal in the equipment. From previous experience,
my equipment being on does not cause the radios to squeal. They
squeal sometimes on AM with my equipment out of the picture.

I did some tests to see if proximity of the power boxes to the mics
had anything to do with it. Bringing the boxes close to mics did not
cause any squealing of distortion/hum of any kind.

Today I turned on the radios and they were squealing but my equipment
was fine. The only thing that's changed is the 7 pin cable position
and location of the power boxes for the mics. These are both out in
the hall now. Yesterday the cables were in a random heap on the floor
of the tracking room. Today they are uncoiled in a more or less
straight path out into the hall to the power boxes. Perhaps that may
have something to do with it, too early to say right now.

I've done the tests you speak off, turning off equipment one by one,
they don't effect the problem at all. Turning off the monitor does
relieve the hum, but that is a different problem due to the magnetism
rather than RMI that I can control more easily.

[Truth]

On Sep 13, 2:28 pm, Eeyore
wrote:
Truth wrote:
Eeyore wrote:

A DH Labs DI ? I can't find anything by googling. Is it active or passive ?

Sorry, that wasn't clear. DH labs 12 feet 110 Ohm XLR used as the
connection between the preamps and the sound card.

What the heck is a "DH labs 12 feet 110 Ohm XLR".

Are you using daft audiophool 'snake oil' cables ?

I'd get rid of those straight away and use something sensible and reliable.

Graham

I've tried three different brand of cables. I get the problem with
different brands such as Monster and Nady.

[Truth]

On Sep 13, 2:39 pm, Eeyore
wrote:
Truth wrote:
Eeyore wrote:

It sounds like they've been pumping you full of nonsense.

No they are correct. When my LCD monitor is on I can hear a definite
hum or buzz. When I turn it off it goes away, so I turn it off while
recording.

That proves the sum total of nothing other than poor product design. I know, I'm a
pro-audio designer and pretty expert in RF interference matters actually.

Because the microphones use magnetism to function they are
prone to these problems.

Rubbish. The fact the mics have a magnet inside is totally and completely irrelevant to
RF pickup. Where the hell do you get this crap from ? What is especially relevant by the
way is inductance and 'loop area'.

They sound good when they work,

As some badly designed equipment (especially esoteric hi-fi) often does.

Graham

I know that the RFI and magnetism problems are different. What I
meant to say is that the problems with dimmers, fluorescent lights,
motors, converters in close proximity and such are due to magnetism.
This is the reason why turning on my LCD monitor introduces hum. The
RFI problems are not related to magnetism. I know this. You just
misunderstood what I said is all, though I wasn't entirely clear I
admit. The mics do have problems with these things though they are
not due to RFI but a separate issue.

[Truth]

On Sep 13, 1:32 pm, (Scott Dorsey) wrote:
Truth wrote:
The cable connecting the ribbon mic to it's dedicated power supply is
a 7 pin cable provided by Royer Labs. Could the problem originate in
the power and get intensified by the Mic's Power Supply and cables, or
the mic itself?

If it's an RF problem, it has nothing to do with the power system.

I'm not so sure it _is_ an RF problem, though.

When you heard this squealing sound on an AM radio tuned to 790, was
your audio gear operating at the time?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Last night I heard content, a radio talk show, along with the usual
squeal. The content was very faint compared to the squeal but it was
present indicating this is an RFI problem.

[Richard Crowley]

"Truth" wrote...
Yes, If I turn off the equipment, the radio still squeals and vice
versa, if I turn off the radios in the house the equipment still
squeals. The squeal changes pitch though it stays high pitched. It's
the same type of squeal you get when you turn the dial between
stations. Just a badly received signal I suspect. It's always
changing, coming and going and moving about. I don't know why the
squeal exists in the first place that is something I want to learn
more about. The problem only occurs when the station is squealing. I
only found out yesterday that this was a RF problem so I haven't had
the chance to do much testing or research into yet. If the problem is
related to the radio station as I suspect now, then I will call them
and let them know.

So record 10-20 seconds of this "squeal" and put it online
somewhere where we can hear it. Are you *sure* you mean
that you hear "squeal" on your radio receiver between stations?
I would describe inter-station noise (both AM and FM) as "hiss"
not "squeal".

If you are *really* hearing a "squeal" between stations on your
radio, and with all your audio equipment turned off, I would
strongly suspect that there is nothing particularly wrong with
your audio equipment. Where are you? (So we can figure
out what 790AM radio station is.) Do you know how far from
the transmitter tower you are.

I checked the radio this morning, no squeal. I turned the equipment
on and tested with both preamps, no squeal. They coincide. Last
night when I was hearing the squeal the equipment was also squealing.
The squeal from a badly received station and the sound I'm hearing
when the equipment acts up are very similar if not identical, like a
modified version of it.

That would be a strong indicator to me that the problem is external
and there may be nothing particularly wrong with your audio equipment.

[Truth]

On Sep 13, 2:39 pm, Eeyore
wrote:
Truth wrote:
Eeyore wrote:

It sounds like they've been pumping you full of nonsense.

No they are correct. When my LCD monitor is on I can hear a definite
hum or buzz. When I turn it off it goes away, so I turn it off while
recording.

That proves the sum total of nothing other than poor product design. I know, I'm a
pro-audio designer and pretty expert in RF interference matters actually.

Because the microphones use magnetism to function they are
prone to these problems.

Rubbish. The fact the mics have a magnet inside is totally and completely irrelevant to
RF pickup. Where the hell do you get this crap from ? What is especially relevant by the
way is inductance and 'loop area'.

They sound good when they work,

As some badly designed equipment (especially esoteric hi-fi) often does.

Graham

I got it from he

http://svconline.com/mag/avinstall_u...ontrolling_rf/

And also reading on Royers site the documentation for the mics.

Snip from Royer:

"All ribbon microphones employ magnetic components as a basis for
their operation. All microphones that utilize magnets are somewhat
susceptible to induced magnetic radiation, especially from alternating
magnetic fields such as those found in motors, transformers and video
monitors. These fields can be strong enough to induce an alternating
electric current in microphones that in turn gets amplified by the
preamplifier. This is the same effect that plagues electric guitars,
especially those with single coil pick-ups. If you experience this
phenomenon, locate the source of the radiated field and move it away,
shut it off, or simply move the mic away from the offending device."

I'll be the first to admit I don't understand entirely how this all
works exactly, I'm not an electrical engineer, but the mics do have
problems with things such as those I mentioned. It's not rubbish as
you suggest, I've experienced the video monitor problem first hand.
It seems the RF and magnetism is all connected actually, though this
particular problem is different from the usual hum and buzz... here's
a snip from the article:

"Unintentional RF sources are most commonly devices that produce an
electrical spark. Sparks are potent RF generators-before vacuum tubes,
they were the heart of radio transmitters-that splatter energy over a
wide frequency spectrum. Any wiring connected to the spark source not
only conducts the RF but also acts as a transmitting antenna to
radiate it. Common sparking sources include electric welders, brush-
type motors, relays and switches of all kinds. Less obvious sources
include arcing or corona discharge in power line insulators (common in
seashore areas or under humid conditions), malfunctioning fluorescent
or neon lighting and automobile spark plugs. Lightning is the ultimate
spark and a well known producer of momentary interference to virtually
anything electronic.

Other unintentional RF generators are devices that abruptly interrupt
current flow using some form of electronic switching. The most common
examples are light dimmers, fluorescent lights, TV or computer CRT
displays and any piece of equipment using a switching power supply or
"clock" oscillator (computers and other digital devices). The RFI
source may be in the same room as your system or, worse yet, it may be
a part of your system.

RFI symptoms The tolerance of equipment to RFI depends largely on how
well it is designed. Generally, symptoms will appear when sufficient
RF energy reaches an active device-IC, transistor, tube-inside the
equipment. The energy can arrive in two ways: radiation or conduction.
As it travels through the air, internal equipment wiring can act as a
receiving antenna and deliver RF voltages directly to an active
device. This is most common in equipment with plastic or wood
enclosures that have no RF shielding ability. Because any wire can
become a receiving antenna, RF energy can also be conducted into the
equipment's active devices via any wire leaving or entering the
equipment. Interference can also arrive via any wire coming into the
building. Because power, telephone, CATV and even driveway intercom,
landscape lighting, or outdoor loudspeaker lines also behave as
outdoor antennas, they are often teeming with AM radio signals and
other interference. The most troublesome sources, however, are
frequently inside the building where the interference is distributed
via the power wiring. At high frequencies, a building's power wiring
behaves like a system of misterminated transmission lines gone
berserk, reflecting RF energy back and forth throughout the power
wiring until it is eventually absorbed or radiated. The RF does not
just follow the green ground wire back to the earth ground rod and
magically disappear.

RF power line noise is coupled through equipment power supplies into
system ground conductors. Therefore, significant noise voltage will
inevitably exist between the chassis grounds of any two devices in AC-
powered systems, whether safety grounded or not. This is the dominant
noise source in most systems, not noise picked up by cables as is so
widely believed. When this noise flows in the shield of unbalanced
signal cables, the voltage drop directly adds to the signal as shown
in Figure 1."

[Eeyore]

Scott Dorsey wrote:

Eeyore wrote:
Paul Stamler wrote:
"Scott Dorsey" wrote in message

It is a known problem with all microphones, however I did not have any
problem when I reviewed these mikes. I keyed a 1W handie-talkie on 146 MHz
up within a few inches of the mike (which is my regular RF test).

AM or FM ?

No modulation. (The HT is actually FM modulated, but usually just a blast
of A0 shows up problems).

You're mistaken.

You absolutely MUST test susceptibility with a modulated signal (and preferably AM).
If some equipment is bothered by carrier alone then it's really rubbish.

Graham

[Eeyore]

Truth wrote:

Eeyore wrote:
Truth wrote:
Eeyore wrote:

A DH Labs DI ? I can't find anything by googling. Is it active or passive ?

Sorry, that wasn't clear. DH labs 12 feet 110 Ohm XLR used as the
connection between the preamps and the sound card.

What the heck is a "DH labs 12 feet 110 Ohm XLR".

Are you using daft audiophool 'snake oil' cables ?

I'd get rid of those straight away and use something sensible and reliable.


I've tried three different brand of cables. I get the problem with
different brands such as Monster and Nady.

No surprise there. All cable is largely the same.

So why did you buy this over-priced DH Labs audiophool cable ?

Graham

[Eeyore]

Truth wrote:

Eeyore wrote:
Truth wrote:
Eeyore wrote:

It sounds like they've been pumping you full of nonsense.

No they are correct. When my LCD monitor is on I can hear a definite
hum or buzz. When I turn it off it goes away, so I turn it off while
recording.

That proves the sum total of nothing other than poor product design. I know, I'm a
pro-audio designer and pretty expert in RF interference matters actually.

Because the microphones use magnetism to function they are
prone to these problems.

Rubbish. The fact the mics have a magnet inside is totally and completely irrelevant to
RF pickup. Where the hell do you get this crap from ? What is especially relevant by the
way is inductance and 'loop area'.

They sound good when they work,

As some badly designed equipment (especially esoteric hi-fi) often does.


I know that the RFI and magnetism problems are different. What I
meant to say is that the problems with dimmers, fluorescent lights,
motors, converters in close proximity and such are due to magnetism.

Electro-magnetic induction.


This is the reason why turning on my LCD monitor introduces hum.

Almost certainly not the case actually. You shouldn't make assumptions like that. LCD monitors
themselves have virtually zero magnetic field output.

Graham

[Scott Dorsey]

Truth wrote:

Yes, If I turn off the equipment, the radio still squeals and vice
versa, if I turn off the radios in the house the equipment still
squeals. The squeal changes pitch though it stays high pitched. It's
the same type of squeal you get when you turn the dial between
stations. Just a badly received signal I suspect. It's always
changing, coming and going and moving about. I don't know why the
squeal exists in the first place that is something I want to learn
more about. The problem only occurs when the station is squealing. I
only found out yesterday that this was a RF problem so I haven't had
the chance to do much testing or research into yet. If the problem is
related to the radio station as I suspect now, then I will call them
and let them know.

Find out where the squeal is. It's not coming from the radio station.
It's coming from some other RF source.

I checked the radio this morning, no squeal. I turned the equipment
on and tested with both preamps, no squeal. They coincide. Last
night when I was hearing the squeal the equipment was also squealing.
The squeal from a badly received station and the sound I'm hearing
when the equipment acts up are very similar if not identical, like a
modified version of it. Why the squeal without the content such as
voice or music I wonder though? I was only able to hear the content
very faintly beneath all the squeal. Usually I can't hear the content
just the squeal.

If this is the case, and if you have verified that your equipment is not
causing the squeal, you need to find where the source of the squeal is.

Get a portable radio, then start popping breakers on the main panel in
the building until the squeal goes away. If all of your power is out
and the squeal is still there, use the directional loopstick antenna on
the radio to try and get a beam on where the noise source is.

The noise source is not the radio station but it's something else spewing
out trash. Your goal is to find it. The engineer at the radio station
might be willing to help, though, since it's interfering with his station
too!
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Eeyore wrote:
Scott Dorsey wrote:

Eeyore wrote:
Paul Stamler wrote:
"Scott Dorsey" wrote in message

It is a known problem with all microphones, however I did not have any
problem when I reviewed these mikes. I keyed a 1W handie-talkie on 146 MHz
up within a few inches of the mike (which is my regular RF test).

AM or FM ?

No modulation. (The HT is actually FM modulated, but usually just a blast
of A0 shows up problems).

You're mistaken.

You absolutely MUST test susceptibility with a modulated signal (and preferably AM).
If some equipment is bothered by carrier alone then it's really rubbish.

Turning the carrier on or off isn't sufficient modulation?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

On Sep 13, 10:33 pm, Truth wrote:

Last night I heard content, a radio talk show, along with the usual
squeal. The content was very faint compared to the squeal but it was
present indicating this is an RFI problem.

Do you have a recorder other than your computer setup that you could
use to record a little of the radio with the squeal and post a small
sample that we could download and hear for ourselves? I don't think we
need a high resolution high fidelity recording, just an MP3 file made
from a portable recorder with a built-in mic would probably suffice.
I, for one, would probably like to be sure of what you're calling a
"squeal." There could be a very good clue there.

[Mike Rivers]

On Sep 13, 10:12 pm, Truth wrote:

I've done the tests you speak off, turning off equipment one by one,
they don't effect the problem at all. Turning off the monitor does
relieve the hum, but that is a different problem due to the magnetism
rather than RMI that I can control more easily.

In that case, it's a pretty sure bet that there's an RF source nearby
that's sometimes on and sometimes off. Is this a private house? An
industrial building? An apartment? Are you near an airport or medical
facility? Furniture factory? Welding shop?

[Eeyore]

Scott Dorsey wrote:

Eeyore wrote:
Scott Dorsey wrote:
Eeyore wrote:
Paul Stamler wrote:
"Scott Dorsey" wrote in message

It is a known problem with all microphones, however I did not have any
problem when I reviewed these mikes. I keyed a 1W handie-talkie on 146 MHz
up within a few inches of the mike (which is my regular RF test).

AM or FM ?

No modulation. (The HT is actually FM modulated, but usually just a blast
of A0 shows up problems).

You're mistaken.

You absolutely MUST test susceptibility with a modulated signal (and preferably AM).
If some equipment is bothered by carrier alone then it's really rubbish.

Turning the carrier on or off isn't sufficient modulation?

No. Think about it.

Graham

[Truth]

On Sep 13, 10:57 pm, "Richard Crowley" wrote:
"Truth" wrote...
Yes, If I turn off the equipment, the radio still squeals and vice
versa, if I turn off the radios in the house the equipment still
squeals. The squeal changes pitch though it stays high pitched. It's
the same type of squeal you get when you turn the dial between
stations. Just a badly received signal I suspect. It's always
changing, coming and going and moving about. I don't know why the
squeal exists in the first place that is something I want to learn
more about. The problem only occurs when the station is squealing. I
only found out yesterday that this was a RF problem so I haven't had
the chance to do much testing or research into yet. If the problem is
related to the radio station as I suspect now, then I will call them
and let them know.

So record 10-20 seconds of this "squeal" and put it online
somewhere where we can hear it. Are you *sure* you mean
that you hear "squeal" on your radio receiver between stations?
I would describe inter-station noise (both AM and FM) as "hiss"
not "squeal".

If you are *really* hearing a "squeal" between stations on your
radio, and with all your audio equipment turned off, I would
strongly suspect that there is nothing particularly wrong with
your audio equipment. Where are you? (So we can figure
out what 790AM radio station is.) Do you know how far from
the transmitter tower you are.

I checked the radio this morning, no squeal. I turned the equipment
on and tested with both preamps, no squeal. They coincide. Last
night when I was hearing the squeal the equipment was also squealing.
The squeal from a badly received station and the sound I'm hearing
when the equipment acts up are very similar if not identical, like a
modified version of it.

That would be a strong indicator to me that the problem is external
and there may be nothing particularly wrong with your audio equipment.

This is the station:
http://www.michiguide.com/dials/rad-s/wsgw.html

This is a private house in a semi rural area. There are mostly farms
around.

[Mark]

On Sep 14, 9:31 am, Eeyore
wrote:
Scott Dorsey wrote:
Eeyore wrote:
Scott Dorsey wrote:
Eeyore wrote:
Paul Stamler wrote:
"Scott Dorsey" wrote in message

It is a known problem with all microphones, however I did not have any
problem when I reviewed these mikes. I keyed a 1W handie-talkie on 146 MHz
up within a few inches of the mike (which is my regular RF test).

AM or FM ?

No modulation. (The HT is actually FM modulated, but usually just a blast
of A0 shows up problems).

You're mistaken.

You absolutely MUST test susceptibility with a modulated signal (and preferably AM).
If some equipment is bothered by carrier alone then it's really rubbish.

Turning the carrier on or off isn't sufficient modulation?

No. Think about it.

Graham- Hide quoted text -

- Show quoted text -

yes it is..

it is 100% AM modulation and it will make a click or a thump in the
audio instead of tone but can still be easily detected by ear...

Tone modulated AM may be more convient to make a quantitative
measurment but on off keying will also work for a qualitative
test.... it just makes thumps instead of a tone...

Mark

[Mark]

On Sep 14, 10:36 am, Truth wrote:
On Sep 13, 10:57 pm, "Richard Crowley" wrote:





"Truth" wrote...
Yes, If I turn off the equipment, the radio still squeals and vice
versa, if I turn off the radios in the house the equipment still
squeals. The squeal changes pitch though it stays high pitched. It's
the same type of squeal you get when you turn the dial between
stations. Just a badly received signal I suspect. It's always
changing, coming and going and moving about. I don't know why the
squeal exists in the first place that is something I want to learn
more about. The problem only occurs when the station is squealing. I
only found out yesterday that this was a RF problem so I haven't had
the chance to do much testing or research into yet. If the problem is
related to the radio station as I suspect now, then I will call them
and let them know.

So record 10-20 seconds of this "squeal" and put it online
somewhere where we can hear it. Are you *sure* you mean
that you hear "squeal" on your radio receiver between stations?
I would describe inter-station noise (both AM and FM) as "hiss"
not "squeal".

If you are *really* hearing a "squeal" between stations on your
radio, and with all your audio equipment turned off, I would
strongly suspect that there is nothing particularly wrong with
your audio equipment. Where are you? (So we can figure
out what 790AM radio station is.) Do you know how far from
the transmitter tower you are.

I checked the radio this morning, no squeal. I turned the equipment
on and tested with both preamps, no squeal. They coincide. Last
night when I was hearing the squeal the equipment was also squealing.
The squeal from a badly received station and the sound I'm hearing
when the equipment acts up are very similar if not identical, like a
modified version of it.

That would be a strong indicator to me that the problem is external
and there may be nothing particularly wrong with your audio equipment.

This is the station:http://www.michiguide.com/dials/rad-s/wsgw.html

This is a private house in a semi rural area. There are mostly farms
around.- Hide quoted text -

- Show quoted text -

How far is the station transmitter (not the studio) from your audio
gear?

what frequency is the squeal?

Mark

[Truth]

On Sep 14, 9:26 am, Mike Rivers wrote:
On Sep 13, 10:12 pm, Truth wrote:

I've done the tests you speak off, turning off equipment one by one,
they don't effect the problem at all. Turning off the monitor does
relieve the hum, but that is a different problem due to the magnetism
rather than RMI that I can control more easily.

In that case, it's a pretty sure bet that there's an RF source nearby
that's sometimes on and sometimes off. Is this a private house? An
industrial building? An apartment? Are you near an airport or medical
facility? Furniture factory? Welding shop?

Where I'm recording is a private house in a rural area with farms
nearby. The room has been treated for internal sound, there is no
treatment specifically for RF interference. Mostly just fiber glass
around the room in various traps.

There is no industrial building for miles. There are scattered oil
pumps and such. There is one of those small power grid bases a few
miles away (like one of those mini bases they send the power lines
from). The nearest airport is a small local one for small planes
located about 3 miles away. The medical center is about 4 miles
away. A larger airport with more commercial planes is located about
14 miles away. The largest factory and industrial complex is about 6
miles away.

[Don Pearce]

On Fri, 14 Sep 2007 07:36:35 -0700, Truth
wrote:

On Sep 13, 10:57 pm, "Richard Crowley" wrote:
"Truth" wrote...
Yes, If I turn off the equipment, the radio still squeals and vice
versa, if I turn off the radios in the house the equipment still
squeals. The squeal changes pitch though it stays high pitched. It's
the same type of squeal you get when you turn the dial between
stations. Just a badly received signal I suspect. It's always
changing, coming and going and moving about. I don't know why the
squeal exists in the first place that is something I want to learn
more about. The problem only occurs when the station is squealing. I
only found out yesterday that this was a RF problem so I haven't had
the chance to do much testing or research into yet. If the problem is
related to the radio station as I suspect now, then I will call them
and let them know.

So record 10-20 seconds of this "squeal" and put it online
somewhere where we can hear it. Are you *sure* you mean
that you hear "squeal" on your radio receiver between stations?
I would describe inter-station noise (both AM and FM) as "hiss"
not "squeal".

If you are *really* hearing a "squeal" between stations on your
radio, and with all your audio equipment turned off, I would
strongly suspect that there is nothing particularly wrong with
your audio equipment. Where are you? (So we can figure
out what 790AM radio station is.) Do you know how far from
the transmitter tower you are.

I checked the radio this morning, no squeal. I turned the equipment
on and tested with both preamps, no squeal. They coincide. Last
night when I was hearing the squeal the equipment was also squealing.
The squeal from a badly received station and the sound I'm hearing
when the equipment acts up are very similar if not identical, like a
modified version of it.

That would be a strong indicator to me that the problem is external
and there may be nothing particularly wrong with your audio equipment.

This is the station:
http://www.michiguide.com/dials/rad-s/wsgw.html

This is a private house in a semi rural area. There are mostly farms
around.

So this is an AM station that squeals when it is dark? That would be
typical of tropospheric propagation which typically brings in distant
stations during the hours of darkness. There is probably one somewhere
within a hundred miles or so at a 9kHz frequency offset from your
local station. A bit of non-linearity is all it takes to generate
that 9kHz beat tone.

Can you confirm the frequency of the squeal by looking at your DAW?

d

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

[Scott Dorsey]

Truth wrote:

This is a private house in a semi rural area. There are mostly farms
around.

Farms with electric fences? With ultrasonic crow-scaring devices? Both
are BIG sources of RF troubles.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Eeyore]

Mark wrote:

Eeyore wrote:
Scott Dorsey wrote:
Eeyore wrote:
Scott Dorsey wrote:
Eeyore wrote:
Paul Stamler wrote:
"Scott Dorsey" wrote in message

It is a known problem with all microphones, however I did not have any
problem when I reviewed these mikes. I keyed a 1W handie-talkie on 146 MHz
up within a few inches of the mike (which is my regular RF test).

AM or FM ?

No modulation. (The HT is actually FM modulated, but usually just a blast
of A0 shows up problems).

You're mistaken.

You absolutely MUST test susceptibility with a modulated signal (and preferably AM).
If some equipment is bothered by carrier alone then it's really rubbish.

Turning the carrier on or off isn't sufficient modulation?

No. Think about it.

yes it is..

it is 100% AM modulation and it will make a click or a thump in the
audio instead of tone but can still be easily detected by ear...

Not if the modulation might only have resulted in say a -40 tone.

Are you seriously trying to tell me you can reliably determine a SINGLE -40dB click ? How
about a -60dB thump. The idea it's a reliable test is plain silly.

The relevant IEC immunity test requires a modulated signal of course (it didn't at one time
but they fixed the oversight).

Graham

[Mike Rivers]

On Sep 14, 10:53 am, Truth wrote:

Where I'm recording is a private house in a rural area with farms
nearby. The room has been treated for internal sound, there is no
treatment specifically for RF interference. Mostly just fiber glass
around the room in various traps.

I wouldn't expect a copper-lined house in a residential area. Do any
of those farms have an electric fence? Or one of those Invisible Fence
systems for keeping a dog in the yard?

The nearest airport is a small local one for small planes
located about 3 miles away.

If they have a radar, at 3 miles, it could be hitting you, but it
wouldn't be continuous noise, it would be cyclical as the radar
antenna swept through your direction. I think Scott's suggestion of
walking around with a portable radio is a good one.

A shorter cable between the mic and its power supply might reduce the
RF pickup, but it's unlikely that it would eliminate it entirely. If
that's actually where the "antenna" is, chances are it's the mic
rather than the cable.

I don't remember now. Did you test with the same setup but with a mic
othe rthan the Royer?

If you trace the pickup to the microphone system, maybe if you talk to
Royer, they can send you a dummy plug that you can put on the mic end
of the cable instead of the mic. If the noise goes away that would
point to the mic as the pickup. If it doesn't, then it's the cable or
something in the power supply box.

I think you're getting the idea of what you need to do.

[Truth]

On Sep 14, 9:19 am, Mike Rivers wrote:
On Sep 13, 10:33 pm, Truth wrote:

Last night I heard content, a radio talk show, along with the usual
squeal. The content was very faint compared to the squeal but it was
present indicating this is an RFI problem.

Do you have a recorder other than your computer setup that you could
use to record a little of the radio with the squeal and post a small
sample that we could download and hear for ourselves? I don't think we
need a high resolution high fidelity recording, just an MP3 file made
from a portable recorder with a built-in mic would probably suffice.
I, for one, would probably like to be sure of what you're calling a
"squeal." There could be a very good clue there.

Here's a sample of the squeal recorded through the chain I listed. I
have not recorded off the radio yet. In this sample I was able to
capture both the squeal and the faint content of the talk show.
Normally it's just the squeal as I mentioned. You can download it
from this site:

http://files-upload.com/files/502446/royerradio.mp3

[Eeyore]

Truth wrote:

Here's a sample of the squeal recorded through the chain I listed. I
have not recorded off the radio yet. In this sample I was able to
capture both the squeal and the faint content of the talk show.
Normally it's just the squeal as I mentioned. You can download it
from this site:

http://files-upload.com/files/502446/royerradio.mp3

That's nothing to do with radio.

It sounds more like the artifacts you get in a computer's audio from screen
operations.

Graham

[Scott Dorsey]

Truth wrote:

Here's a sample of the squeal recorded through the chain I listed. I
have not recorded off the radio yet. In this sample I was able to
capture both the squeal and the faint content of the talk show.
Normally it's just the squeal as I mentioned. You can download it
from this site:

http://files-upload.com/files/502446/royerradio.mp3

I wouldn't call that a squeal as much as a high frequency pulse. It's not
repetitive. It's not your gear breaking out into oscillation. It's time
to start popping breakers and walking around with the radio.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Truth]

On Sep 14, 10:59 am, (Scott Dorsey) wrote:
Truth wrote:

This is a private house in a semi rural area. There are mostly farms
around.

Farms with electric fences? With ultrasonic crow-scaring devices? Both
are BIG sources of RF troubles.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Interesting possibility, didn't know those existed.

[Paul Stamler]

"Mike Rivers" wrote in message
oups.com...
On Sep 13, 10:12 pm, Truth wrote:

I've done the tests you speak off, turning off equipment one by one,
they don't effect the problem at all. Turning off the monitor does
relieve the hum, but that is a different problem due to the magnetism
rather than RMI that I can control more easily.

In that case, it's a pretty sure bet that there's an RF source nearby
that's sometimes on and sometimes off. Is this a private house? An
industrial building? An apartment? Are you near an airport or medical
facility? Furniture factory? Welding shop?

Radar station?

Peace,
Paul

[Truth]

On Sep 14, 11:49 am, Eeyore
wrote:
Truth wrote:
Here's a sample of the squeal recorded through the chain I listed. I
have not recorded off the radio yet. In this sample I was able to
capture both the squeal and the faint content of the talk show.
Normally it's just the squeal as I mentioned. You can download it
from this site:

http://files-upload.com/files/502446/royerradio.mp3

That's nothing to do with radio.

It sounds more like the artifacts you get in a computer's audio from screen
operations.

Graham

Screen operations? You mean the video monitor? This squeal is
present with all the other equipment turned off except for the preamp
and mic. This includes the computer and monitor.

If your theory was right, then I would experience this problem with
other mics and not just the ribbon microphone. In addition, you can
hear the radio program in the background. That's not a radio, what
you hear is only what's being picked up by the microphone or something
in the chain. How would you explain the radio program in the
background?



How also would you explain that this only happens

[Paul Stamler]

"Don Pearce" wrote in message
...

So this is an AM station that squeals when it is dark? That would be
typical of tropospheric propagation which typically brings in distant
stations during the hours of darkness. There is probably one somewhere
within a hundred miles or so at a 9kHz frequency offset from your
local station. A bit of non-linearity is all it takes to generate
that 9kHz beat tone.

In the US stations are spaced 10kHz apart.

Peace,
Paul

[Truth]

On Sep 14, 11:34 am, Mike Rivers wrote:
On Sep 14, 10:53 am, Truth wrote:

Where I'm recording is a private house in a rural area with farms
nearby. The room has been treated for internal sound, there is no
treatment specifically for RF interference. Mostly just fiber glass
around the room in various traps.

I wouldn't expect a copper-lined house in a residential area. Do any
of those farms have an electric fence? Or one of those Invisible Fence
systems for keeping a dog in the yard?

The nearest airport is a small local one for small planes
located about 3 miles away.

If they have a radar, at 3 miles, it could be hitting you, but it
wouldn't be continuous noise, it would be cyclical as the radar
antenna swept through your direction. I think Scott's suggestion of
walking around with a portable radio is a good one.

A shorter cable between the mic and its power supply might reduce the
RF pickup, but it's unlikely that it would eliminate it entirely. If
that's actually where the "antenna" is, chances are it's the mic
rather than the cable.

I don't remember now. Did you test with the same setup but with a mic
othe rthan the Royer?

If you trace the pickup to the microphone system, maybe if you talk to
Royer, they can send you a dummy plug that you can put on the mic end
of the cable instead of the mic. If the noise goes away that would
point to the mic as the pickup. If it doesn't, then it's the cable or
something in the power supply box.

I think you're getting the idea of what you need to do.

Ok thanks, I will ask them about that. I did try it with some other
microphones. These other microphones are condenser microphones and
dynamic microphones. They have never had this squeal/whistle.

[Scott Dorsey]

Truth wrote:
On Sep 14, 10:59 am, (Scott Dorsey) wrote:
Truth wrote:

This is a private house in a semi rural area. There are mostly farms
around.

Farms with electric fences? With ultrasonic crow-scaring devices? Both
are BIG sources of RF troubles.

Interesting possibility, didn't know those existed.

Your noise sounds more like noise from a computer than from either one,
but it's going to be something goofy like that.

Electric fences are LOTS of fun and can be heard for miles, as a repeating
pulsed buzz sound, especially if they are poorly maintained and have a lot
of leakage to ground.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Truth wrote:

Ok thanks, I will ask them about that. I did try it with some other
microphones. These other microphones are condenser microphones and
dynamic microphones. They have never had this squeal/whistle.

Ever had an electric guitar in the studio?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Truth]

On Sep 14, 2:05 pm, Truth wrote:
On Sep 14, 11:49 am, Eeyore
wrote:

Truth wrote:
Here's a sample of the squeal recorded through the chain I listed. I
have not recorded off the radio yet. In this sample I was able to
capture both the squeal and the faint content of the talk show.
Normally it's just the squeal as I mentioned. You can download it
from this site:

http://files-upload.com/files/502446/royerradio.mp3

That's nothing to do with radio.

It sounds more like the artifacts you get in a computer's audio from screen
operations.

Graham

Screen operations? You mean the video monitor? This squeal is
present with all the other equipment turned off except for the preamp
and mic. This includes the computer and monitor.

If your theory was right, then I would experience this problem with
other mics and not just the ribbon microphone. In addition, you can
hear the radio program in the background. That's not a radio, what
you hear is only what's being picked up by the microphone or something
in the chain. How would you explain the radio program in the
background?

How also would you explain that this only happens

....

How also would you explain that this only happens with the Royer
Microphones and not with any of my other microphones? I've tested
about 4 or 5 other microphones. They are condenser and dynamic
microphones rather than ribbons. Two of the other micrphones are tube
microphones and they don't squeal like this. I also have a tube
preamp and it doesn't squeal with the other microphones.

[Truth]

On Sep 14, 2:12 pm, (Scott Dorsey) wrote:
Truth wrote:

Ok thanks, I will ask them about that. I did try it with some other
microphones. These other microphones are condenser microphones and
dynamic microphones. They have never had this squeal/whistle.

Ever had an electric guitar in the studio?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Yes, I have used an electric guitar, not often but I have. Never had
problems using it with my equipment.