Unfortunately, there’s one potential hiccup in this cenario, assuming you want to do it right: the need to demonstrate compliance with Federal Communications Commission (FCC) emission
rules. As a hobbyist, FCC rules aren’t something you’re
likely to worry much about since you’re allowed to build
up to five devices of a single design for personal use with
no testing whatsoever.
Once you go over five units, however, things change.
At this level, the FCC requires verification of any electronic
device operating above 9 kHz since it could possibly
produce unwanted interference to other local devices.
Devices that do not use radio transmitters are referred to
as “unintentional radiators,” and the testing bar is lower
for them than it is for “intentional radiators” — devices that
include radios like Wi-Fi modules or Bluetooth.
There are a few exceptions for some specialized
applications, and you may be able to avoid FCC
requirements by declaring that your product is a
subassembly or a kit of some sort. In almost all other
cases, hobbyists who want to bring electronics products to
market in some form or another are subject to the rules
set forth in Part 15 of Title 47 CFR.
It’s tempting to just skip FCC testing and hope no one
complains, but it’s a risk that can come with major
consequences. If you ship a product without an FCC
number from an approved FCC lab, you can be fined up
to $10,000 per day per device, plus a year in jail if the
FCC decides you did it intentionally.
Unfortunately, the cost of demonstrating compliance
can be steep as well. Devices that require verification or a
“Declaration of Conformity” — that is unintentional
radiators — can be tested for a few thousand dollars. For
$10,000 to as much as $30,000. Costs can escalate
quickly if your product fails, and FCC compliance test
reports usually offer little to no insight into the causes of a
Get Ahead of the Curve
The best bet for avoiding these unpleasant scenarios is
to perform FCC pre-compliance testing on your soon-to-be
product before sending it off to the test house. The advent
of low cost USB based real time spectrum analyzers from
top-tier manufacturers means that pre-compliance testing
is now within reach for even the most budget-strapped
hobbyist or entrepreneur.
Pre-compliance testing gives you the opportunity to
catch compliance problems early, and greatly improves
the probability of a successful first pass of full EMC
compliance testing without re-design. It also lets you
identify problem areas early on, and then evaluate the
effect of modifications as your design evolves from
prototype and moves into production.
Since pre-compliance testing is not required by the
FCC, the equipment used can be noncompliant and have
lower accuracy and dynamic range than the compliant
receivers used by approved labs if sufficient margin is
applied to the test results. Pre-compliance testing requires
the following test equipment:
• Spectrum analyzer with peak detector (quasi-peak
• Preamplifier (optional)
conducted emissions testing