Building Wireless Community Networks
by Rob Flickenger


This errata page lists errors outstanding in the most recent printing.

If you have technical questions or error reports, you can send them to
booktech@oreilly.com.  Please specify the printing date of your copy.

This page was updated February 11, 2002.


Here's a key to the markup:
	[page-number]: serious technical mistake
	{page-number}: minor technical mistake
	<page-number>: important language/formatting problem
	(page-number): language change or minor formatting problem
	?page-number?: reader question or request for clarification



Confirmed errors:


{77}
  

In section 6.2.3 of Rob Flickinger's book, he calculates the total system gain as
below:

"Next, add up all of your gains (radios + antennas + amplifiers) and subtract your
losses (cable length, connectors, lightning arrestors, and miscellaneous other
losses). Let's assume you are using Orinoco Silver cards (15dBm), no amplifiers, with
a 12dBi sector on one side, and a 15dBi yagi on the other. We'll assume you're using
one meter of LMR-400 and a lightning arrestor on each side, allowing 0.25dB loss for
each connector, and 1dB for each pigtail. Since all of the units are in dB, we can
use simple addition and subtraction:

  radio - pigtail - arrestor - connector - cable - connector + antenna
  Site A: 15 - 1 - 1.25 - 0.25 - 0.22 - 0.25 + 12 = 24.03
  Site B: 15 - 1 - 1.25 - 0.25 - 0.22 - 0.25 + 15 = 27.03
  A + B = 51.06 total gain "
It is incorrect to add in the radio transmit power twice.  If you are 
calculating total path gain, then the power gain figure of the receiving 
radio is immaterial.

The correct calculation is below:

radio - pigtail - arrestor - connector - cable - connector + antenna
Site A: 15 - 1 - 1.25 - 0.25 - 0.22 - 0.25 + 12 = 24.03
- pigtail - arrestor - connector - cable - connector + antenna
Site B: - 1 - 1.25 - 0.25 - 0.22 - 0.25 + 15 = 12.03
A + B = 36.06 total gain