Re: Idea: Sidestepping low-power broadcast regulations with infrared

[Steve Schear]

Another possibility occurred to me.  It might be possible to use the 
802.11-like devices for this purpose.  The problem for this application 
with Wi-Fi is its focus on high data rate and therefore low process 
gain.  But there is no inherent reason why almost the same circuits 
(perhaps even the off-the-shelf PC cards themselves) couldn't be 
re-purposed for used at lower effective data rates and higher process gain 
for much greater range and interference immunity while still operating 
within the FCC Part 15 guidelines.

As I recall most of the notebook cards have a max output of about 80 
mW.  Each of the 5 channels in the 2.4 GHz band can support up to 11 
mbps.  If you assume that you will use this for stereo broadcasting then 
only 128 kbps offers a pretty good quality .mp3  This is a data rate ratio 
of 85 :1 or about 18 dB.  For every 6 dB of link margin improvement a 
signal's range is doubled.  18 dB should, all other things being 
equivalent, extend the device range by 8 times.  (If data rates were 
lowered to those now common for PCS and used for that sort of purpose, link 
margins would expand by another 9-12 dB.)

steve