[EE] RF bench equipment for pre-cert testing

[Bob Blick]

I'm looking for equipment recommendations for a test bench that will be
useful in getting a portable(battery operated) product ready for FCC
certification. I know a spectrum analyzer and an antenna are number one,
but what else?

This is for a product that has a transmitter in it, but I'm also
interested in testing non-intentional radiators as well.

Budget is around $10000 or $15000 top. Do I have to buy used stuff? I
hate used test equipment.

Thanks for any input!

Cheerful regards,

Bob

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[M. Adam Davis]

A spectrum analyzer and antenna are pretty much all that's needed for
FCC pre testing. You'll want to set up the device to be as noisy as
it could possibly be given then design so you can find out the maximum
RF output, and not jsut the 'idle' rf output. the real FCC test will
also require you to do this.

We would start with a simple small wideband rf probe and the analyzer,
and move it all around the device to find the peak frequencies and
note approximate output power.

We then had a field out back with a large ground plane (4 or 6" wire
mesh, grounded to all test equipment (disconnected when not in use!).
Use the calibrated antenna (IIRC) 6 meters from the device with the
spectrum analyzer and get snapshots of it in the ranges of interest.
Change the position of the device, and do it again until you get at
least 6 orientations (cube) but prefereably more.

Show that in all the areas of interest the device is lower than the FCC maximum.

We never bothered with a mechanized product rotator, but I know some
companies that use them, and a few that even do all 3 axis with
hundreds of readings.

The devices we were making had such a low RF signature that this was
all that was needed to make sure we weren't accidently creating
antennas and frequencies on the board that went out of range.

Most of these were unintentional radiators. We did start producing
zigbee/wifi/bluetooth designs before I left, and we'd actually follow
this process, then send them to a lab if we found anything peaking for
analysis rather than buy the equipement required for troubleshooting
(they were starting to be a big company, and I suppose their
accountants decided it's better to spend thousands on consultants for
each project than spend 10x as much once and be done with it... Guns
and butter, guns and butter...).

-Adam

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