It depends on a number of factors. Here in the Colonies, our beloved
version of OFCOM has defined three types of unlicensed radiators:
Incidental, Unintentional, and Intentional. Incidental are those that
make RF as part of their operation but don't need to and it serves no
purpose in their operation. Basically noisemakers like PWM motor
controls or arcing HV lines. Unintentional are those that create RF as
part of their operation but do not intend or need to radiate it.
Computers are probably the best example, a one-tube regenerative RX is
another. Intentional are those that make and radiate RF as an integral
part of their operation. Remote sensing thermometers and weather
stations are a good example ... so is Wayne's 1 mw TX. They are all
regulated by Part 15 of the FCC's regulations. 2.4 and 5.6 GHz Wi-Fi and
Bluetooth devices are all covered by Part 15. There are also duty cycle
limits in some regions of the spectrum.
A big factor is the antenna, and one requirement of Part 15 is that the
user be unable to modify it. That's why I used the term "Part 15
Engineering," one will have to test and certify that the device meets
the Part 15 requirements including the field strength. 150 mW on 6 MHz
with a 0 dBi antenna will produce a field strength of about 0.07 V/m at
30 m which is way over the limit. 1 mW will be about 0.006 V/m or so.
A very limited antenna with something like -15 to -20 dBi "gain" would
probably bring the field strength down sufficiently, provided the user
can't get to it to modify it.
I'd consider randomizing the TX frequencies within a very small [~5-10
kHz?] "band" [like padding the xtals] and making the RX tuneable over
that band so a group could have individual "conversations" such as at a
Scout meeting or in a classroom.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
On 10/19/2019 12:29 AM, CUTTER DAVID wrote:
Wayne was looking for 1mW output. How does that equate in regard to the regs?
David G3UNA
On 18 October 2019 at 22:58 Fred Jensen <k6...@foothill.net> wrote:
If they're unlicensed, they will be intentional radiators subject to
47CFR15 Subpart C [15.201 et seq] which imposes field strength limits
that vary with frequency. 15.201(b) may also require certification.
Depending on choice of frequency, 150 mW may be way too high since in
the 1.7 - 30 MHz range, the limit is 30 uV/m at 30 m. I think Wayne has
hit on a great idea, it's just going to take some Part 15 engineering.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
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