"Frank Gilliland" wrote in message
...
On Mon, 25 Apr 2005 23:24:49 -0400, "BobC"
wrote in :


Ok, let's consider the circuitry in front of the speakers: Assuming
the speakers do not have their own power amps, the amps are enclosed
in a fully (or almost fully) shielded case. The only unshielded lines
into the case are pairs; i.e, only common mode currents can enter the
case. Excluding the power line (filtered by the power supply) and the
phone line (filtered by the modem transformer), the only means of
entry is through the speaker wires connected to a very low impedance
power amp. And assuming the power amp uses feedback (and that
rectification of the RF occurs at the power amp stage), it would take
just as much power to distort the amps' intended output (and therefore
cause audio feedback of the demodulated RF) as it would to drive the
speakers directly. That also assumes an efficient antenna -- resonant
lengths of speaker wire.

Now if the speakers are amplified externally (amp in the speakers),
they are more than likely driven by a shielded cable. Regardless,
almost all low-level preamps are designed for high common-mode
rejection (we're talking 60-90 dB+ at each stage); and since the low
impedance of the power amp is no less suseptible to RFI than if the
amp was enclosed in the computer case, it would -still- take a
considerable amount of RF power on the lines to drive the speakers.

This is not just theory but fact -- they are designed this way for the
specific purpose of eliminating that annoying AC hum and digital RFI
that permeates most houses, -especially- the horrific noise generated
by computer monitors and light dimmers. "Overloaded DAC's"? I don't
think so, Bob. How do you overload a DAC? YOU will have to do better
than THAT.

Common mode shmommen mode.
In a perfect world your model works.
But you're not explaining why I can eat up 2 out of 4 hi end audio cards.
And if you're not cognizent of how you eat a DAC's lunch, go read.
You may also notice that modems don't always use transformers anymore.
Modems are just as susceptible to rf on the lines as anything else.
Sound cards have fairly high imp, non-balanced inputs and hi gain.
Your model assumes no (-) or (+) supply rail changes from rf.
Your model only survives within the puter itself.
Add rf on a mic, spkr or phone lead and you have a great receiver.
It doesn't need to overload the main audio amp, just a prior stage.
The xformers you mentioned have enough cap across the windings to pass rf.
The leads you mentioned are not the only ones connected to the puter.
There are monitors, scanners, mice, cameras etc.
_____________________
Authorization to transmit with a CB is automatically revoked when the
station is operating illegally. Shall I cite the code?

Not necessary. Just prove that the station is illegal.
It wouldn't hurt to have some decent field strength readings.
Maybe a witness attesting to the actual use of an amp?
_____________________
Which is all well and good but until you've satisfied the feds that
your consumer grade stuff is properly filtered, they aren't going to
bother
sending anyone out to check.

They won't send anyone out regardless. They don't care about the CB.
But they do suck up to the ham community, and if it turns out that
this guy has a license they may indeed take action if they find he is
operating illegally (i.e, using power on the CB).

Which brings us back to doing the necessary part of filtering before
calling.
_____________________
So far, I've not read from Jade anything that remotely suggests he or she
has a serious interference complaint involving another radio service.

I read "fire service" radio and I invited Jade to tell me what he/she
considers a fire service radio.

Scanners don't count.

Actually, they do. If someone is causing interference to a scanner,
it's very possible..... nay, -likely-..... that he will also cause
interference to an emergency service radio that happens to be in close
proximity. This is a problem because while the cops chase the killer
with the gun running through the neighborhood, Andy the Amphead keys
up and the guy gets away (or worse) because the cops lose comm.

Are you trying to present that a "real radios" front end isn't any better
than a scanner?

I'm sure the folks paying for those $3000 MA/COM's & Motorolas
would love to know about that. Even the Kenwood & Icom users.

You're also back to calling the guy guilty before you have proof.
Reread the part about innocent till proven guilty.
______________________
I haven't seen any real proof that the neighbor is running an illegal
station.
Jade has not indicated other neighbors are complaining of similar events.
Such complaints might induce me to think the cb'er is running power.

Then that would be a good question to ask. So ask it.

I believe I already did.
_______________________
Unless or until someone brings more convincing proof of the allegations,
I'm going with the notion it's a singular complaint due the quality of the
consumer electronics invloved.

You'll excuse me if I happen to believe in "reasonable doubt" &
"due process" instead of conjecture & unfounded finger pointing.
bc


How about "civic responsibility"?

How about Constitutional Law?
bc

On Tue, 26 Apr 2005 22:20:28 -0400, "BobC"
wrote in :


"Frank Gilliland" wrote in message
.. .
On Mon, 25 Apr 2005 23:24:49 -0400, "BobC"
wrote in :


Ok, let's consider the circuitry in front of the speakers: Assuming
the speakers do not have their own power amps, the amps are enclosed
in a fully (or almost fully) shielded case. The only unshielded lines
into the case are pairs; i.e, only common mode currents can enter the
case. Excluding the power line (filtered by the power supply) and the
phone line (filtered by the modem transformer), the only means of
entry is through the speaker wires connected to a very low impedance
power amp. And assuming the power amp uses feedback (and that
rectification of the RF occurs at the power amp stage), it would take
just as much power to distort the amps' intended output (and therefore
cause audio feedback of the demodulated RF) as it would to drive the
speakers directly. That also assumes an efficient antenna -- resonant
lengths of speaker wire.

Now if the speakers are amplified externally (amp in the speakers),
they are more than likely driven by a shielded cable. Regardless,
almost all low-level preamps are designed for high common-mode
rejection (we're talking 60-90 dB+ at each stage); and since the low
impedance of the power amp is no less suseptible to RFI than if the
amp was enclosed in the computer case, it would -still- take a
considerable amount of RF power on the lines to drive the speakers.

This is not just theory but fact -- they are designed this way for the
specific purpose of eliminating that annoying AC hum and digital RFI
that permeates most houses, -especially- the horrific noise generated
by computer monitors and light dimmers. "Overloaded DAC's"? I don't
think so, Bob. How do you overload a DAC? YOU will have to do better
than THAT.

Common mode shmommen mode.
In a perfect world your model works.


It's not -my- model, and it works in the real world just fine. If it
didn't there would be so much noise coming from the speakers that they
would be almost useless.


But you're not explaining why I can eat up 2 out of 4 hi end audio cards.


I have my suspicions.....


And if you're not cognizent of how you eat a DAC's lunch, go read.


Read what? A DAC datasheet? Heck, I get those as junk mail every month
(and I wish they would quit sending them). Maybe you should learn what
a DAC actually does before you start spouting off about subjects you
know very little about. DAC stands for "Digital to Analog Converter",
and the only way to overload them (aside from blowing them up with too
much Vcc) is to push all the inputs to the same logic level, in which
case you will not get audio from the output but a steady DC signal. So
how is it that you think that you can overload a soundcard's DAC with
AM (analog) RF and get demodulated audio from the output? If you can
then you got some serious voodoo happening.


You may also notice that modems don't always use transformers anymore.
Modems are just as susceptible to rf on the lines as anything else.


You might have noticed yourself that the modem is usually a seperate
and isolated card, that the line inputs always include RFI protection
by law (transformer or chokes), that they have excellent common-mode
signal rejection, and that the line impedance is quite low when it's
off-hook. Any RF on the phone line stops at the modem for the same
reason that I explained about the speakers -- because they are
designed to reject environmental RF hash. The only way a stray RF
signal can hop the phone line, skip past the modem, infiltrate the
power supply and drive the sound card, with a demodulation stage
happening somewhere in that path, is if the RF has some significant
power.


Sound cards have fairly high imp, non-balanced inputs and hi gain.


Unbalanced lines use shielded cables.


Your model assumes no (-) or (+) supply rail changes from rf.


Your criticizm assumes no power supply regulation, no bypass caps on
the chips, no capacitance between power traces and the ground plane
layer, no inductive losses from the straight traces on the bus, etc.
IOW, you are reaching.


Your model only survives within the puter itself.
Add rf on a mic, spkr or phone lead and you have a great receiver.


Not even close for the reasons I already explained (and apparently you
couldn't understand). Yet I forgot to mention that the only way for
the impedance of an RF signal to be low enough to force it's way past
the hardware, the line must be both resonant -and- terminate at the
computer at a low-impedance node, -and- provide a signal with
sufficient strength to defeat the protections and/or output power.
That's a pretty tall order for a speaker line -- especially when you
realize that most of the time the excess line is wound up and tied,
making a pretty good RF choke.


It doesn't need to overload the main audio amp, just a prior stage.


I didn't say "overload", I said "distort". There is a difference. And
while I have no problem with RFI interfering with a stage prior to the
output, the most obvious route is the feedback loop which I already
addressed. Or weren't you paying attention?


The xformers you mentioned have enough cap across the windings to pass rf.


No they don't, simply because they either have electrostatic shielding
between the layers (somewhat old-fashioned) or use tandem windings on
the bobbin (much more common these days, and a whole lot cheaper). But
they do have enough -inductance- to choke any RF on the line.


The leads you mentioned are not the only ones connected to the puter.
There are monitors,


Shielded.


scanners,


Shielded, (except for USB, which is a balanced pair).


mice,


Shielded.


cameras


USB.


etc.


Keyboard: Shielded.
Power cable: Filtered.

And you should be aware that the same engineering standards used to
prevent RFI from -exiting- the computer case also serve to prevent RFI
from -entering- the computer case.

Got any more lame excuses?


_____________________
Authorization to transmit with a CB is automatically revoked when the
station is operating illegally. Shall I cite the code?

Not necessary. Just prove that the station is illegal.
It wouldn't hurt to have some decent field strength readings.
Maybe a witness attesting to the actual use of an amp?


How about just setting up a legal CB radio next to the computer and
see if it causes the same problems described by the OP? I have done so
many times and never experienced a problem. In fact, I have a Tram 60
sitting right beside my computer and use it frequently with no ill
effects to the computer, although the computer does tend to cause RFI
to the radio.....


_____________________
Which is all well and good but until you've satisfied the feds that
your consumer grade stuff is properly filtered, they aren't going to
bother
sending anyone out to check.

They won't send anyone out regardless. They don't care about the CB.
But they do suck up to the ham community, and if it turns out that
this guy has a license they may indeed take action if they find he is
operating illegally (i.e, using power on the CB).

Which brings us back to doing the necessary part of filtering before
calling.


A local AM station (KGA, I think) had a problem a few years back. They
were pumping so much power that you could hear the audio sounding from
the chain-link fence at the nearby school. Are you suggesting that it
is the school's responsibilty to filter the fence?


_____________________
So far, I've not read from Jade anything that remotely suggests he or she
has a serious interference complaint involving another radio service.

I read "fire service" radio and I invited Jade to tell me what he/she
considers a fire service radio.

Scanners don't count.

Actually, they do. If someone is causing interference to a scanner,
it's very possible..... nay, -likely-..... that he will also cause
interference to an emergency service radio that happens to be in close
proximity. This is a problem because while the cops chase the killer
with the gun running through the neighborhood, Andy the Amphead keys
up and the guy gets away (or worse) because the cops lose comm.

Are you trying to present that a "real radios" front end isn't any better
than a scanner?

I'm sure the folks paying for those $3000 MA/COM's & Motorolas
would love to know about that. Even the Kenwood & Icom users.


If the harmonic falls on the operating frequency then it doesn't
matter how well the front end is built -- interference is the
inevitable result. But even the best receivers are not immune to
overload.


You're also back to calling the guy guilty before you have proof.
Reread the part about innocent till proven guilty.


I'm convinced with the information that was given. I suspect that you
are also convinced but are simply making excuses. If you are not
convinced then either you have very little experience or are woefully
ignorant about the subject.


______________________
I haven't seen any real proof that the neighbor is running an illegal
station.
Jade has not indicated other neighbors are complaining of similar events.
Such complaints might induce me to think the cb'er is running power.

Then that would be a good question to ask. So ask it.

I believe I already did.


I looked back through the thread and I saw no such question. Perhaps
my news server didn't pick it up -- care to cite the post?


_______________________
Unless or until someone brings more convincing proof of the allegations,
I'm going with the notion it's a singular complaint due the quality of the
consumer electronics invloved.

You'll excuse me if I happen to believe in "reasonable doubt" &
"due process" instead of conjecture & unfounded finger pointing.
bc


How about "civic responsibility"?

How about Constitutional Law?


How about it? Although it has fallen by the wayside during the Bush
administration, there is nothing I suggested that would deprive anyone
of their Constitutional rights. I'm not a court and I don't execute
due process. But if I have good reason to believe that someone is
violating a law then I don't keep my mouth shut because of some
whacko's ultra-literal interpretation of the Constitution. Due process
is not pre-empted by a presumption of innocence -- OTOH, due process
must be initiated before it can occur, and reasonable suspicion is
enough to begin that process. That's the law. If you don't like it,
work to change it. If you don't then quit whining and learn to live
with the system the way it is.






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From: (Frank=A0Gilliland)
On Tue, 26 Apr 2005 22:20:28 -0400, "BobC" wrote
in :
(How about Constitutional Law? )

How about it? Although it has fallen by the

wayside during the Bush administration, there

is nothing I suggested that would deprive

anyone of their Constitutional rights. I'm not a

court and I don't execute due process. But if I

have good reason to believe that someone is

violating a law then I don't keep my mouth

shut because of some whacko's ultra-literal

interpretation of the Constitution. Due process

is not pre-empted by a presumption of

innocence -- OTOH, due process must be

initiated before it can occur, and reasonable

suspicion is enough to begin that process.

That's the law. If you don't like it, work to

change it. If you don't then quit whining and

learn to live with the system the way it is.

Fwiw, Due Process (according to the Supreme Court) is a difficult thing
to define. It has been said DP is merely the law of the land. The Fifth
and Fourteenth Amendments refer only to federal agency protection with
regards to DP. DP is basically how and why laws are enforced, and
questions "Is the law fair?" as in "does a law presume guilt?" The end
result is the law (as it applies to all persons) must be clear and
concise and it absolutely MUST have a presumption of innocence to comply
with Due Process.

On Wed, 27 Apr 2005 09:47:08 -0400, (I
AmnotGeorgeBush) wrote in
:

From: (Frank*Gilliland)
On Tue, 26 Apr 2005 22:20:28 -0400, "BobC" wrote
in :
(How about Constitutional Law? )

How about it? Although it has fallen by the

wayside during the Bush administration, there

is nothing I suggested that would deprive

anyone of their Constitutional rights. I'm not a

court and I don't execute due process. But if I

have good reason to believe that someone is

violating a law then I don't keep my mouth

shut because of some whacko's ultra-literal

interpretation of the Constitution. Due process

is not pre-empted by a presumption of

innocence -- OTOH, due process must be

initiated before it can occur, and reasonable

suspicion is enough to begin that process.

That's the law. If you don't like it, work to

change it. If you don't then quit whining and

learn to live with the system the way it is.

Fwiw, Due Process (according to the Supreme Court) is a difficult thing
to define. It has been said DP is merely the law of the land. The Fifth
and Fourteenth Amendments refer only to federal agency protection with
regards to DP. DP is basically how and why laws are enforced, and
questions "Is the law fair?" as in "does a law presume guilt?" The end
result is the law (as it applies to all persons) must be clear and
concise and it absolutely MUST have a presumption of innocence to comply
with Due Process.


I think the disagreement is with how "presumed innocent" is applied.
The phrase simply means that the accused must be aquitted unless guilt
can be proven. It does not prohibit any presumption of guilt by the
accuser, the victim, the press, the public, or anyone else except the
judge/jury; i.e, presumption of innocence applies only to those that
are charged with making the -determination- of guilt or innocence.

Now as for "due process".....

According to the 1855 Supreme Court opinion to which you referred,
"due process of law" applies to any law that is (1) not otherwise
unconstitutional, and (2) consistent with "those settled usages and
modes of proceeding existing in the common and statute law..."

For an example of the first condition, Bush's Patriot Act is a direct
violation of "due process of law" because it infringes on the right to
a fair and speedy trial, the right to contest all accusatory evidence,
the right to an attorney, presumption of innocence, etc, etc..... it's
a quite a long list. Therefore, the Act is unconstitutional under the
Fifth Amendment because it's unconstitutional in other respects. It's
kind of a double-whammy.

As for the second condition, Bush's Patriot Act is a voyage into
uncharted legal waters. He fabricated new laws that have no foundation
in common or statutory law. And while the Act itself is statutory,
most of its laws are unprecedented; i.e, they are not derived from
"settled usages and modes of proceeding". Bush's Patriot Act is, once
again, in violation of the Fifth Amendment because it contains laws
that are not based on any legal precedent.

In fact, the passing of the Act by Congress was itself a violation of
the Fifth Amdendment because it was done in direct contradiction to
the Supreme Court's interpretation of the Amendment: "It is manifest
that it was not left to the legislative power to enact any process
which might be devised. The article is a restraint on the legislative
as well as on the executive and judicial powers of the government, and
cannot be so construed as to leave Congress free to make any process
'due process of law,' by its mere will."

Ok, that was way off topic, but you get the drift.







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Yep, I do get the drift. Beautifully illustrated with a great analogy.
You ought write that up in a neat letter to your local editor concerning
the (un)Patriot Act,,or even a national editor.

On Thu, 28 Apr 2005 11:27:29 -0400, (I
AmnotGeorgeBush) wrote in
:

Yep, I do get the drift. Beautifully illustrated with a great analogy.
You ought write that up in a neat letter to your local editor concerning
the (un)Patriot Act,,or even a national editor.


Thank you. Plagiarize it as you see fit.






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"BobC" wrote in message
...

"Frank Gilliland" wrote in message
...
On Mon, 25 Apr 2005 23:24:49 -0400, "BobC"
wrote in :


Ok, let's consider the circuitry in front of the speakers: Assuming
the speakers do not have their own power amps, the amps are enclosed
in a fully (or almost fully) shielded case. The only unshielded lines
into the case are pairs; i.e, only common mode currents can enter the
case. Excluding the power line (filtered by the power supply) and the
phone line (filtered by the modem transformer), the only means of
entry is through the speaker wires connected to a very low impedance
power amp. And assuming the power amp uses feedback (and that
rectification of the RF occurs at the power amp stage), it would take
just as much power to distort the amps' intended output (and therefore
cause audio feedback of the demodulated RF) as it would to drive the
speakers directly. That also assumes an efficient antenna -- resonant
lengths of speaker wire.

Now if the speakers are amplified externally (amp in the speakers),
they are more than likely driven by a shielded cable. Regardless,
almost all low-level preamps are designed for high common-mode
rejection (we're talking 60-90 dB+ at each stage); and since the low
impedance of the power amp is no less suseptible to RFI than if the
amp was enclosed in the computer case, it would -still- take a
considerable amount of RF power on the lines to drive the speakers.

This is not just theory but fact -- they are designed this way for the
specific purpose of eliminating that annoying AC hum and digital RFI
that permeates most houses, -especially- the horrific noise generated
by computer monitors and light dimmers. "Overloaded DAC's"? I don't
think so, Bob. How do you overload a DAC? YOU will have to do better
than THAT.

Common mode shmommen mode.
In a perfect world your model works.
But you're not explaining why I can eat up 2 out of 4 hi end audio cards.

Most often, even wahat you consider "high end" cards do not have the audio
sheild grounded properly. If you are running into problems try running the
sheild to case ground or better yet use transformers.

And if you're not cognizent of how you eat a DAC's lunch, go read.

Prove yourself wrong and go see. There are countless DAC's sitting under
big power AM/FM transmitters with much more RF saturation than the common
splatter box can produce from a neighbor's house. AND if RF creeps into the
front end of a DAC you will NOT hear it (program audio) over the speakers,
it will simply raise the error rate and cause the audio to be glitched or
muted.

You may also notice that modems don't always use transformers anymore.

Most do, motherboard integrated ones are starting not to. Which sucks IMHO,
if something goes wrong "mother nature" it's new mobo time!

Modems are just as susceptible to rf on the lines as anything else.

No kidding, but their design dictates that unless their audio output is run
to the speakers, audio will not get ino the sound card.

Sound cards have fairly high imp, non-balanced inputs and hi gain.

If the input is not being used it is shorted to "ground" as stated earlier
this is not always a trusty ground, Shorting it to true ground or shutting
that input off in the control panel will solve the problem. if one input or
output sheild is grounded to a trustworthy ground it will all be good as
they share ground with no buffering. If this input is tied to an output
device the impedance of the output device is usually low enough to negate
problems

Your model assumes no (-) or (+) supply rail changes from rf.

HEH there are no +/- rails in consumer audio cards, they are single ended.
Until you get into the external pro cards you will see this.

Your model only survives within the puter itself.
Add rf on a mic, spkr or phone lead and you have a great receiver.

Ground the sheild and the problem will go away.

Tell us about that phone lead and why.

It doesn't need to overload the main audio amp, just a prior stage.



The xformers you mentioned have enough cap across the windings to pass rf.

To what?

The leads you mentioned are not the only ones connected to the puter.
There are monitors, scanners, mice, cameras etc.

All not associated with audio, concentrate on the audio card. Hell, my cell
phone drives them nuts till they are properly taken care of. one ground and
the problem goes away.

Another question to raise is is there even a ground? how old is the house
and has the ground rod rotted away, better yet, is there even a ground rod?

Chad

_____________________
Authorization to transmit with a CB is automatically revoked when the
station is operating illegally. Shall I cite the code?

Not necessary. Just prove that the station is illegal.
It wouldn't hurt to have some decent field strength readings.
Maybe a witness attesting to the actual use of an amp?
_____________________
Which is all well and good but until you've satisfied the feds that
your consumer grade stuff is properly filtered, they aren't going to
bother
sending anyone out to check.

They won't send anyone out regardless. They don't care about the CB.
But they do suck up to the ham community, and if it turns out that
this guy has a license they may indeed take action if they find he is
operating illegally (i.e, using power on the CB).

Which brings us back to doing the necessary part of filtering before
calling.
_____________________
So far, I've not read from Jade anything that remotely suggests he or she
has a serious interference complaint involving another radio service.

I read "fire service" radio and I invited Jade to tell me what he/she
considers a fire service radio.

Scanners don't count.

Actually, they do. If someone is causing interference to a scanner,
it's very possible..... nay, -likely-..... that he will also cause
interference to an emergency service radio that happens to be in close
proximity. This is a problem because while the cops chase the killer
with the gun running through the neighborhood, Andy the Amphead keys
up and the guy gets away (or worse) because the cops lose comm.

Are you trying to present that a "real radios" front end isn't any better
than a scanner?

I'm sure the folks paying for those $3000 MA/COM's & Motorolas
would love to know about that. Even the Kenwood & Icom users.

You're also back to calling the guy guilty before you have proof.
Reread the part about innocent till proven guilty.
______________________
I haven't seen any real proof that the neighbor is running an illegal
station.
Jade has not indicated other neighbors are complaining of similar events.
Such complaints might induce me to think the cb'er is running power.

Then that would be a good question to ask. So ask it.

I believe I already did.
_______________________
Unless or until someone brings more convincing proof of the allegations,
I'm going with the notion it's a singular complaint due the quality of
the
consumer electronics invloved.

You'll excuse me if I happen to believe in "reasonable doubt" &
"due process" instead of conjecture & unfounded finger pointing.
bc


How about "civic responsibility"?

How about Constitutional Law?
bc

On Wed, 27 Apr 2005 10:22:40 -0500, "Chad Wahls"
wrote in :

snip
Most often, even wahat you consider "high end" cards do not have the audio
sheild grounded properly.


Very good point. Some cards have shield connectors that are DC
isolated from the chassis to prevent ground loops with other audio
equipment. In such cards the shield is coupled to chassis ground with
caps, but line noise can be a problem (and the cap must be shorted)
because the caps may not large enough to fully shunt low frequencies.
But the caps do shunt RF very well, and if they can keep the local AM
broadcast stations out of the soundcard then the neighbor's legal CB
radio shouldn't be a problem.







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"Frank Gilliland" wrote in message
...
On Wed, 27 Apr 2005 10:22:40 -0500, "Chad Wahls"
wrote in :

snip
Most often, even wahat you consider "high end" cards do not have the audio
sheild grounded properly.


Very good point. Some cards have shield connectors that are DC
isolated from the chassis to prevent ground loops with other audio
equipment. In such cards the shield is coupled to chassis ground with
caps, but line noise can be a problem (and the cap must be shorted)
because the caps may not large enough to fully shunt low frequencies.
But the caps do shunt RF very well, and if they can keep the local AM
broadcast stations out of the soundcard then the neighbor's legal CB
radio shouldn't be a problem.




Problem is that they don't do all that well with AM Broadcast. When I was a
conglomo radio engineer we had a 50K FM and a 500W AM in a residential area.
I would get complaints-o-plenty of the AM coming thru computer speakers,
cheapo HT systems and phones. Of course we had to do what we could to
eliminate the problem and usually I would pull the sound card, DC ground it
with 1 ohm 1/4W resistors and the problem went away. 90% of my problems
called in were ratified with proper grounding. Fortunately most of the
construction in the area is newer as that tower used to be outside city
limits but due to urban sprawl it is no longer.

As for my personal soundcards I use pro models with a separate breakout box
that's balanced. The other card in that computer and other computers in the
house are SB audigy models with the mini jacks removed and XLR whips out in
their place. This whip then goes to a breakout box with 6 Jensen
transformers in it 4 for output and 2 for input. The mic input is shorted
down permanently. I have zero noise problems, if you have an Audigy card it
does sound good! You just have to help it out

The transformers....... When radio engineering and upgrading EAS systems in
all the stations I found that all the old receivers that we were throwing
out were loaded with Jensen transformers! What a salvage find!!!!! I had
many-o-dumpster diving missions, then adopted a Chad's gotta pilfer it pile.
Lots of transformers and power supplies were gutted

Chad

On Thu, 28 Apr 2005 09:11:08 -0500, "Chad Wahls"
wrote in :


"Frank Gilliland" wrote in message
.. .
On Wed, 27 Apr 2005 10:22:40 -0500, "Chad Wahls"
wrote in :

snip
Most often, even wahat you consider "high end" cards do not have the audio
sheild grounded properly.


Very good point. Some cards have shield connectors that are DC
isolated from the chassis to prevent ground loops with other audio
equipment. In such cards the shield is coupled to chassis ground with
caps, but line noise can be a problem (and the cap must be shorted)
because the caps may not large enough to fully shunt low frequencies.
But the caps do shunt RF very well, and if they can keep the local AM
broadcast stations out of the soundcard then the neighbor's legal CB
radio shouldn't be a problem.




Problem is that they don't do all that well with AM Broadcast. When I was a
conglomo radio engineer we had a 50K FM and a 500W AM in a residential area.
I would get complaints-o-plenty of the AM coming thru computer speakers,
cheapo HT systems and phones.


Sounds like we had similar jobs -- do the daily checks, fill out the
daily reports, then spend the rest of the day making cables, cleaning
cart machines and waiting for something to break?


Of course we had to do what we could to
eliminate the problem and usually I would pull the sound card, DC ground it
with 1 ohm 1/4W resistors and the problem went away. 90% of my problems
called in were ratified with proper grounding. Fortunately most of the
construction in the area is newer as that tower used to be outside city
limits but due to urban sprawl it is no longer.

As for my personal soundcards I use pro models with a separate breakout box
that's balanced. The other card in that computer and other computers in the
house are SB audigy models with the mini jacks removed and XLR whips out in
their place. This whip then goes to a breakout box with 6 Jensen
transformers in it 4 for output and 2 for input. The mic input is shorted
down permanently. I have zero noise problems, if you have an Audigy card it
does sound good! You just have to help it out


I use the Extigy -- it's great because you can locate the box some
distance away from the noisy computer and ground it directly to the
mixer.

But for complaints to the station, I got them to order a huge box of
4" jumpers that have pigtails to the shield. Just plug them into the
soundcard (or whatever audio equipment is getting the interference),
screw the pigtail to the chassis, and 'presto' -- problem solved. No
invasive surgery, and you're out of the house in a matter of minutes.


The transformers....... When radio engineering and upgrading EAS systems in
all the stations I found that all the old receivers that we were throwing
out were loaded with Jensen transformers! What a salvage find!!!!!


No kidding!


I had
many-o-dumpster diving missions, then adopted a Chad's gotta pilfer it pile.
Lots of transformers and power supplies were gutted


Those old Bogen and Rauland paging amps have some pretty sweet
transformers, too. One of these days we gotta exchange inventory lists
of our scrounge bins.






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