You are reading the rules correctly. While you can increase power with a wider
channel, you also lose power on the receive side when the channel gets wider.
Going from a 5 MHz wide channel to a 10 MHz wide channel you lose 3 dB in
receive. So in that case the power increase is a wash due to the decrease in
receiver signal. This is a power density thing. You will also limit your
ability to move around if you have any interference as well when you have wider
channels. 3 dB gain doubles your power and 3 dB loss cuts your receive signal
level in half.
Thank You,
Brian Webster
www.wirelessmapping.com
www.Broadband-Mapping.com
From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On Behalf
Of Eduardo
Sent: Monday, June 26, 2017 4:00 PM
To: WISPA General List
Subject: [WISPA] EIRP quick question
Hi guys,
We’re reviewing one of our links that is using RocketM365 radio and a RD-3G-26
in each end. The link is using 5MHz channel width.
Here is the question:
Checking the FCC regulation part 90.1321 I found that the limitation of the
EIRP is defined as follow:
§ 90.1321 Power and antenna limits. (a) Base and fixed stations are limited to
25 watts/25 MHz equivalent isotropically radiated power (EIRP). In any event,
the peak EIRP power density shall not exceed 1 Watt in any one-megahertz slice
of spectrum.
What I understand from this text is that for instance, if the link is using a
25 MHz channel then the maximum EIRP is 25 W, and if the link was 10 MHz
channel width then the maximum EIRP is 10 W.
If I’m getting it right, our link can still increase the bandwidth changing the
channel width to 10 or 25 MHz and still comply with the maximum EIRP establish
by the regulation.
I’m interpreting the limitation correctly?
Thanks,
Eduardo Mejia
Webjogger Internet Services
www.webjogger.net
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