[Cerowrt-devel] Cerowrt-devel Digest, Vol 37, Issue 24

[David P. Reed]

Neither 2.4 GHZ nor 5.8 GHz are absorbed more than other bands. That's an old wives tale. The reason for the bands' selection is that they were available at the time. The water absorption peak frequency is 10x higher.

Don't believe what people repeat without checking. The understanding of radio propagation by CS and EE folks is pitiful. Some even seem to think that RF energy travels less far the higher the frequency.

Please don't repeat nonsense.

On Dec 20, 2014, Mike O'Dell <mo at ccr.org> wrote:
>15.9bps/Hz is unlikely to be using simple phase encoding
>
>that sounds more like 64QAM with FEC.
>given the chips available these days for DTV, DBS,
>and even LTE, that kind of processing is available
>off-the-shelf (relatively speaking - compared to 
>writing your own DSP code).
>
>keep in mind that the reason the 2.4 and 5.8 ISM bands
>are where they are is specifically because of the ready
>absorption of RF at those frequencies. the propagation
>is *intended* to be problematic. that said, with 
>good-enough antennas mounted with sufficient stability
>and sufficient power on the TX end and a good enough
>noise floor on the RX end, one can push a bunch of bits
>pretty far.
>
>Bdale Garbee (of Debian fame) had a 10GHz bent-pipe repeater 
>up on the mountain above Colo Spgs for quite some time. X-band
>Gunnplexers were not hard to come by and retune for the
>10GHz ham band. i believe he just FM'ed the Gunnplexer
>with the output of a 10Mbps ethernet chip and ran
>essentially pure Aloha. X-band dishes are relatively 
>small and with just a few stations in the area he had fun.
>
>      -mo
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-- Sent from my Android device with K-@ Mail. Please excuse my brevity.
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