[Elecraft] Looking for volunteer to design a tiny CW transceiver for socially isolated kids/teens

[Fred Jensen]

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 <k6dgw at 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
>>
>>