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[Ham-80211] NLOS on 33 cm

Steve kb9mwr at yahoo.com
Fri Apr 9 20:06:38 UTC 2010


Most hams are probably not well experienced at operation at 900 MHz and above.  Microwave propagation is a different animal for these folks.  

Reading and understanding it and the expected path loss is one thing, and then real world experience is a whole another thing.  You can then compound your confusion on expected performance by realizing that wide band spreading modes are yet another layer to the mix.

I built a simple analog 900 MHz repeater so that I could get a better idea of how signal propagation on the band.  I was rather impressed.  On the same token I was also impressed using the slower Aerocomm FHSS units on 900 MHz.  But trying to draw comparisons between narrow to wide is a bad plan.

The XR-9 is a logical step for the average ham, with a modest tower.  The versatility in data rates and ability to change the channel width from the default of 20 MHz spreading to a half-rate of 10 MHz and even a quarter rate of 5 MHz is ideal.

Overall in all the experimentation of wide band spread spectrum at 900 MHz and 2.4 GHz, from the Proxim Symphony, origional 900 MHz WaveLan, Ubiquiti Bullet to the XR-9, I feel the average ham will be mildly disappointed.

All this stuff works great if you can get a central node/AP up high on a commercial tower.

I have experienced the difference between 1 watt and adding a 10 watt BDS on both bands.  For the average ham, living in the city with a modest tower, this does improve things significantly, and provides something usable.

In light of the recent spread spectrum rule change, I would highly appreciate if TAPR would consider getting behind a BDA project.

I would appreciate if the ARRL would clarify how spread spectrum fits into the existing band plans on 902 and above.

Steve, KB9MWR


      



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