On Sat, 28 Apr 2018 13:46:47 -0400, Paul wrote:

====snip====

For a desktop, you can get a plugin USB nano adapter to add BT (I have a
couple, with only 6 foot reach - these are the kind of electronics
devices I refer to as "rubbish").

https://en.wikipedia.org/wiki/Bluetooth

Ranges of Bluetooth Devices by Class

Class 1 100mW 20dBm ~100 meters
Class 2 2.5mW 4dBm ~10 meters
Class 3 1mW 0dBm ~1 meters


Assuming an omni-directional antenna (therefore all of the same gain),
that power level versus range table is total and utter ********.

Assuming the power levels for each class are correct, the range figures
should increase from the 1mW 0dBm end of the table at 1 metre range via
1.5 metres (2.5mW +4dBm) to 10 metres at 100mW +20dBm.

To achieve ranges of 1, 10 and 100 metres from class 3 to class 1,
starting at a power level of 1mW 0dBm for class 3, class 2 would have to
be 100mW +20dBm and class 3 would need to use a power of 10W +40dBm!

Clearly, this last requirement suggests something is very wrong with the
initial power level requirement for the 1 metre range since a 100mW
requirement looks a more plausible figure for a 100 metre range although
an even more plausible figure is likely to be 300mW for a 100 metres,
therefore a 30 metre range at 100mW seems a more likely specification for
an extended range BT device.

If we assume a 30m range using 100mW (+20dBm), then 10mW (+10dBm)
corresponds to a 10m range and 1mW (0dBm) to a 3 metre range, which looks
to be a much better range spread for the different classes of BT devices
with each magnitude increase of Tx power corresponding to real world half
magnitude increases of range going from 3 metres out to a 30 metre limit.

--
Johnny B Good