FCC and AM noise

[Man-wai Chang]

Which FCC standard governs emission of noise that affects AM radio receiver?

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[Paul]

Which FCC standard governs emission of noise that affects AM radio
receiver?

http://en.wikipedia.org/wiki/Title_47_CFR_Part_15

"Unintentional radiators" <--- this is yours

"Unlicensed broadcasting"

On the standard AM broadcast band, transmission is limited to
100 milliwatts of power (with restrictions on size, height and
type of antenna)

There are a whole slew of standards, and this is an
area that an engineer can specialize in. I worked with a
person, who did this work full time, and he even had an
anechoic chamber set up for doing the measurements. If
you're doing this testing, in the hope of shipping your
product world wide, then there are many standards you
would have to meet. FCC part 15 is just one of them.

http://www.coilws.com/AppNotes/Line6.html

This is an example of how they make the measurements. The walls
help adsorb the RF from the device under test. There is a need to
rotate the device under test, so you can find the worst angle
that it emits at.

http://www.cypress.com/ui/2_5/images/blogs/userimage/EMC_chamber2.jpg

There are all sorts of companies that do testing under contract.

http://www.spectrumcontrol.com/so_emc_testing.asp

I was hoping to find the graph that defines accepted emissions
from zero to many GHz, but haven't managed to find the graph.
I think I've seen at least one wall sized chart, with all
the details on it.

Paul

 

[RayLopez99]

http://www.cypress.com/ui/2_5/images/blogs/userimage/EMC_chamber2.jpg

There are all sorts of companies that do testing under contract.

http://www.spectrumcontrol.com/so_emc_testing.asp

That's an argument perhaps for either offloading the testing to these
companies or offloading the legal risk to the wholesaler buying from
you--let them figure out if the product is legal. I would not be
surprised if every so often some wireless goods get sold in the USA
that do not comply with the myriad of US spectrum laws.

RL

 

[Paul]

That's an argument perhaps for either offloading the testing to these
companies or offloading the legal risk to the wholesaler buying from
you--let them figure out if the product is legal. I would not be
surprised if every so often some wireless goods get sold in the USA
that do not comply with the myriad of US spectrum laws.

RL

I was too far down in the organization chart, to get exposure to all
the steps and details with regard to FCC compliance.

But the staff I talked to:

1) Never said anything derogatory about third party testing.
It was considered equal to our own. In casual conversation, it
would be easy to say "those guys at company X are idiots", but
I never heard anything like that from the local guys. Since our local
guys would play a part in selecting a contractor, it would reflect on
them, if we got idiots.
2) Our in-house test facility could be booked up and full,
just as easily as the contractor facility being booked up and full.
If you missed a booked time slot, there would be a delay until
the next one. The advantage of the in-house facility, is
less shipping delay, and having to pay to house an employee
while on a third party site. I don't know how the pricing
would compare (the in-house facility becomes cheaper for the company,
the more it is used).
3) The equipment manufacturer is ultimately responsible. If
the equipment is stopped at the border, it affects the equipment
manufacturer. And it can cause a delay in *all* product crossing
the border, so it's not something you can afford to screw up.
When that was discussed, our local guys looked genuinely horrified.
If you were the person that caused all company product to be blocked
from the States, even temporarily, I'm sure you'd be fired on the spot.

There are probably horror stories out there about scams or cheating,
but I haven't heard them.

For a small company, that only made one product, and the company name
changed yearly, there could be much richer opportunities.

If it's an established company, there is no percentage in being dishonest.
And suing a contractor, isn't going to make you feel better, when your
company can't ship product. You couldn't possibly get enough compensation
from the contractor, to pay for the damage.

Where the tricks come in, and interpretation is necessary, is in the
equipment configuration. How many cables need to be connected to the
product, to represent a realistic configuration ? Every cable that
you're forced to plug into the equipment, only makes things worse.

*******

For comparison, here is a tale from the motherboard industry

http://www.dailytech.com/Wake+Up+America+Whos+Watching+out+for+EMI/article9052.htm

Paul