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'[OT]: The DAMRT - Macs yes? - PCs no? - FCC ha!!'
2000\08\02@164853 by Dan Michaels

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Speaking if the AM radio test from the other thread,

J-F-T-F-O-I, I just made a test. My AM radio squeels like a pig
when held next to my PC. With my CRT monitor, it doesn't pick up
very much directly in front, but emits a large "raspy" sound along
the left and right [but not top and bottom] portions of the screen.
It also emits a very loud "hiss" when held next to the right hand
side of the case in back - either the HV or possibly switching supply,
I would imagine. It also emits a kind of a "whir" when the HD engages.
[now, I'm monitoring the afternoon thunderstorm moving in - "crashes"
and "pops"].

Now all I have to do is figure out what "squeel", "raspy", "hiss",
"whir", "crash", and "pop" denote.

And so much for FCC certification - he, he. I wonder would anyone's
PC and monitor pass the "Dreaded AM Radio Test".

cheers,
- Dan Michaels
Oricom Technologies
===================

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2000\08\02@165653 by David VanHorn

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>
>And so much for FCC certification - he, he. I wonder would anyone's
>PC and monitor pass the "Dreaded AM Radio Test".

Since they only look at radiated noise ABOVE 30 MHz....
They look at conducted noise below 30.

Rationale, the lower frequencies can't be efficiently radiated unless they
couple out to something.
At least that's how the lab explains it to me.

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2000\08\02@165656 by Severson, Rob

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> Now all I have to do is figure out what "squeel", "raspy", "hiss",
> "whir", "crash", and "pop" denote.

"Squeel", "raspy", "hiss", "whir", "crash", and "pop" denote that the AM
radio is on. Lack of these sounds are an indication that the radio is off or
that you are losing your hearing with age.

:-)

I personally would like to be able to turn up the volume on a thunder storm.
Add more color. Make a rainy drive home into a scene from Fantasia.

I'll adjust my medication now...

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2000\08\02@195906 by Dan Michaels

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DAve VanHorn wrote:
>>
>>And so much for FCC certification - he, he. I wonder would anyone's
>>PC and monitor pass the "Dreaded AM Radio Test".
>
>Since they only look at radiated noise ABOVE 30 MHz....
>They look at conducted noise below 30.
>
>Rationale, the lower frequencies can't be efficiently radiated unless they
>couple out to something.
>At least that's how the lab explains it to me.
>

I wonder - do you think the IF amps in the typical small
AM radio are selective enough that they are *only* responding
to signals in the AM band, or are actually converting higher
frequency emissions? After all the DAMRT really only works
when you hold the radio right up to the DUTs - move back
a couple of feet, and you don't pickup much. [RF is obviously
not my strong suite].

- danM

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2000\08\02@201320 by Dan Michaels

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Rob Severson wrote:
>> Now all I have to do is figure out what "squeel", "raspy", "hiss",
>> "whir", "crash", and "pop" denote.
>
>"Squeel", "raspy", "hiss", "whir", "crash", and "pop" denote that the AM
>radio is on. Lack of these sounds are an indication that the radio is off or
>that you are losing your hearing with age.
>

I'm not so sure about this. There definitely are different sounds,
picked up at different places from different sources. You can localize
them very easily by moving the AM radio around - little palmsize
battery unit. Clearly, the sounds have to do with however it is the
signals being responded to are "modulated".

For instance, I also found that the radio emits a "rurrr" above the
the LEDs on my keyboard, and then a "squeel" when the LEDs are turned
on. Looks like they are lit by a pulsetrain rather than DC.

Also, a few years ago, I found I could use a radio to identify
when my s.w. got stuck in an infinite loop. [course, not all that
hard to do for anyone not asleep].
===================

>I personally would like to be able to turn up the volume on a thunder storm.
>Add more color. Make a rainy drive home into a scene from Fantasia.
>

Probably not too hard to do. Two AM radios with selective loop antennas
at right-angles. Vector display on scope or converted to graphics on PC.
Some kind of neat color coding. Can triangulate and estimate distance
and severity.
=============

>I'll adjust my medication now...
>

Some of us don't need medication to see strange lights and whatnot.

- danM

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2000\08\03@094453 by Severson, Rob

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Dan,

Well, I was *trying* to be a little tongue-in-cheek about AM...

But as long as you are talking about using your radio as a unorthodox test
tool, let me mention what I use:

I use a US$12 RadioShack(tm) mini-amp. Make an input cable (to 1/8 phone
jack) that has clip leads to connect directly to a circuit. Another cable
with a coil for magnetic pickup. One with a solar cell for light pickup
(hardly use this).

Make a serial port snooper to put in-line when experimenting with serial
communication.

You might not think that you would get a lot of useful information this way,
but give it a try. You'd be surprised at how quickly you can determine when
something goes south just by listening to the "noise" that the amplifier
makes audible.

-Rob



> {Original Message removed}

2000\08\03@114250 by Don Hyde

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Lately, we've been working on a project incorporating a 2-watt transmitter.
After accidentally discovering that most PC speakers emitted a loud BRRRP,
and that cheaper monitors shimmied like someone had tickled them whenever
the radio kicked off, we had two useful diagnostic tools on just about
everyone's desk!

(Numerous previous posts...)
>

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2000\08\03@121747 by Dan Michaels

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Rob Severson wrote:
........
>You might not think that you would get a lot of useful information this way,
>but give it a try. You'd be surprised at how quickly you can determine when
>something goes south just by listening to the "noise" that the amplifier
>makes audible.
>

Actually, this was more or less my point. There actually may be some
useful information contained therein - more than just your "tongue-in-
cheek" indication that the radio is turned on.

What is a little unclear - and probably not worth going to the
trouble to investigate - is whether the pickup to the radio is
simply straight into final audio amp stages, or in some manner
goes thru the RF/IF stages. In your RSamp, certainly the former.
But not sure about the radio. Knowing this would broaden the
usability of the "test instrument".

- danM

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2000\08\03@122210 by Dan Michaels

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Don Hyde wrote:
>Lately, we've been working on a project incorporating a 2-watt transmitter.
>After accidentally discovering that most PC speakers emitted a loud BRRRP,
>and that cheaper monitors shimmied like someone had tickled them whenever
>the radio kicked off, we had two useful diagnostic tools on just about
>everyone's desk!
>

There are probably several levels of this -

- direct pickup by audio stage (Rob Severson's RS amp)

- "local" pickup by AM radio (what I was doing), into either
 RF, IF, or audio stages [specifics unknown, but I did have to hold
 the radio right next to the monitor/PC/keyboard to get the signal].

- EM broadcasting - I have seen this before, when sweeping a
 signal generator, and having it picked up by my FM radio on the
 other side of the room [clearly not local field].

Lots of possibilities.

- danM

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2000\08\03@131739 by David VanHorn

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At 10:04 AM 8/3/00 -0600, Dan Michaels wrote:
>Rob Severson wrote:
>........
> >You might not think that you would get a lot of useful information this way,
> >but give it a try. You'd be surprised at how quickly you can determine when
> >something goes south just by listening to the "noise" that the amplifier
> >makes audible.

Back in the early days, we had routines to play music that way.
(pre-pre-pre soundcards)

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2000\08\03@134620 by Phillip Vogel

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David VanHorn wrote:
>
> At 10:04 AM 8/3/00 -0600, Dan Michaels wrote:
> >Rob Severson wrote:
> >........
> > >You might not think that you would get a lot of useful information this way,
> > >but give it a try. You'd be surprised at how quickly you can determine when
> > >something goes south just by listening to the "noise" that the amplifier
> > >makes audible.
>
> Back in the early days, we had routines to play music that way.
> (pre-pre-pre soundcards)

Yep, There was a program called "Jukebox" (if I remember correctly) that ran
on a TRS-80 model 1 and played several tunes through an AM radio. Of course,
the model 1 was befor the FCC regulated computers, and you could shut down the
entire neighborhood's TVs with one of them.....

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2000\08\03@135245 by David VanHorn

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>
>Yep, There was a program called "Jukebox" (if I remember correctly) that ran
>on a TRS-80 model 1 and played several tunes through an AM radio. Of course,
>the model 1 was befor the FCC regulated computers, and you could shut down the
>entire neighborhood's TVs with one of them.....

That may have been before they started complying with the regs, but part 15
has been around for a LONG time.


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2000\08\03@140935 by Phillip Vogel

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David VanHorn wrote:
>
> >
> >Yep, There was a program called "Jukebox" (if I remember correctly) that ran
> >on a TRS-80 model 1 and played several tunes through an AM radio. Of course,
> >the model 1 was befor the FCC regulated computers, and you could shut down the
> >entire neighborhood's TVs with one of them.....
>
> That may have been before they started complying with the regs, but part 15
> has been around for a LONG time.
>

Oh, I know that part 15 has been around a long time, but remember the Mod 1
was around 1978, and there weren't many consumer digital computing devices
generating large amounts of RF back then.  I'm not sure if it was a matter of
lack of enforcement or a hole in the regs, but the 'home' computers of that
age were real noisy. I remember a big scare in the market when the FCC
announced that it would start regulating computers (in the very early
eighties, I think).

Part 15 still has holes in it for various equipment. Electronic music
synthesizers are (or were, a couple of years ago when I last looked) exempt
from the certification requirements. They still must comply, but self testing
with no FCC registration is (or was) OK (and that's much less expensive for
the manufacturer). I don't know who it was, but I'm sure a BIG lobbying effort
led to this.

Hey, maybe if you packaged a TRS80 Mod 1 with an AM radio, you could sneak it
past the FCC as a synthesizer???? The Jukebox program was cool. Definitely the
product of a programmer with WAY too much time on his hands.

P.
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2000\08\03@144358 by Dan Michaels

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Phillip Vogel wrote:
>David VanHorn wrote:
>>
>> At 10:04 AM 8/3/00 -0600, Dan Michaels wrote:
>> >Rob Severson wrote:
>> >........
>> > >You might not think that you would get a lot of useful information
this way,
>> > >but give it a try. You'd be surprised at how quickly you can determine
when
{Quote hidden}

Ha! And, of course, these things no longer work, now that we have
FCC regulated computers. [you will notice the little "FCC ha!!"
business in the title of this thread].

- danM

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2000\08\03@163846 by Peter L. Peres

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>And so much for FCC certification - he, he. I wonder would anyone's
>PC and monitor pass the "Dreaded AM Radio Test".

I only know 2 monitors that did pass this test and both were industrial
grade rackmount units with stamped steel cases (break your back just
lifting them into the rails) internal fans and line and signal filters and
a special front glass with built in steel mesh (so fine you can't see it).
I don' know how much they cost but if you sell your new car then you might
afford one and a half or so. These were not milspec or anything. Just good
quality industrial (lab) grade. Grin.

Apart from that, not even the flip-out LCD screens on camcorders pass the
AM radio test, let alone any CRT based application, nor do plasma
flatscreens, or laptop screens. Just use a higher frequency receiver (HF
will do, between stations).

IMHO a FCC stamp means that the equipment will not cause your fluorescent
light to go out and on by itself when in use, and that it might not
disturb another unit of the same type and make operated right alongside it
(but then it might - and here I could give a few examples).

For example the FCC requirement to have 'the higher harmonics of a radio
transmitter below -35 dB wrt the main carrier' greatly amuses me all the
time. This is not even 100 times down and a 1W transmitter will output
(more than) ~10 mW at 3 x F0, which 10 mW probably exceeds any local or DX
transmitter's field strength by orders of magnitude (two or three orders
of magnitude) for hundreds of meters around the transmitter. And that's
FCCly legal. Yeah. Anyway I live far away from FCC territory.

Peter

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