That's great for us Hams, eh Mike? That power limit is almost enough to
cook a chicken.
73 Jim KI7AY
Michael Miller wrote:
Hey I just had a vendor send me this e-mail (See text below). I was
asking about the FCC rules for both IT professionals vs Amateur Radio
operators. This is the clearest explanation I've seen as of today. I
don't know how old it is. I am willing to say it may be the latest
you can get. There is a note below for Amateur Radio operators to go
too the ARRL website. In case that section is invalid.
Usage and Maximum Power Limit Guidelines in the US under FCC regulations
Before we can go on, first we need to separate the two different
classes of users for Spread Spectrum devices that exist and set some
guidelines of some of the specs.
Consumers and IT Professionals Operating Spread Spectrum (DSSS) gear:
· Users operate under FCC Part 15 rules and regulations.
· Frequencies include 902-928 MHz, 2400-2483.5 and 5725-5850 MHz.
· Maximum Transmitter Power Output (TPO) is 1.0 watt or 30dBm.
· The formula for converting antennas from dBi to dBd is
dBi-2.2=dBd.
There are two different classifications for operation. You'll
commonly hear these modes referred to as Point to Point (PTP) and
Point to Multipoint (PTMP). PTP is when two sites talk only to
themselves. PTMP is when many sites talk to a single core site. Each
of these modes have different EIRP (Effective Isotropic Radiated
Power) limitations.
Point to MultiPoint:
· The maximum EIRP power allowed is 36dBm (4 watts).
· Maximum transmitter power versus largest antenna table for PTMP:
Transmitter RF power Antenna Gain EIRP in watts
30dBm 1W
6dBi 3.98
27dBm 500mW 9dBi 3.98
24dBm 250mW 12dBi 3.98
20dBm 100mW 15dBi 3.98
17dBm 50mW 18dBi 3.98
14dBm 25mW 21dBi 3.98
10dBm 10mW 24dBi 3.98
· Losses from the transmitter via cabling, lightning
suppression, filtration can be removed from the transmitted power dBm
figure. An example here would be say a 30dBm 1 watt amplifier with
100ft of LMR400 (at 6.7dB of loss) brings transmitter power down to
23.3dBm, allowing a 12dBi antenna.
Point to Point:
· Higher EIRP is allowed if the antennas are directional in nature.
· Systems operating in a point-to-point operation may employ
transmitting antennas with directional gain greater than 6 dBi
provided the maximum output power of the transmitter is reduced by 1
dB for every 3 dB that the directional gain of the antenna that
exceeds 6 dBi. Maximum transmitter power versus largest antenna
table for PTP:
Transmitter RF power Antenna Gain EIRP in watts
30dBm 1W
6dBi 3.98
29dBm 800mW 9dBi 6.35
28dBm 630mW 12dBi 10.14
27dBm 500mW 15dBi 15.81
26dBm 398mW 18dBi 25.23
25dBm 316mW 21dBi 40.28
24dBm 250mW 24dBi 62.79
23dBm 200mW 27dBi 100.2
This information is provided as a guideline. If you are not a
professional installer we highly recommend that you read the FCC Part
15 rules and understand them before attempting installations.
Amateur Radio Operators operating under licensed spectrum:
· Users operate under FCC Part 97 rules and regulations.
· Frequencies usable from over-the-counter consumer gear
include the 33cm 902-928 MHz band, the 13cm 2390-2450 MHz band and
the 5cm 5650-5925Mhz band.
· In the 13cm band, 802.11b/g channels 1 thru 6 are the only
channels in the 2390-2450 MHz bandplan.
· Maximum Transmitter Power Output (TPO) is 100 watt or 50dBm.
· You must enable broadcasting of your SSID, which has to
include your callsign.
· Encryption is not currently permitted.
· Only authorized licensed operators should be able to access
Part 97 installed hardware, so care should be taken to prevent
unauthorized users from utilizing said hardware.
It's highly suggested for Amateurs visit the ARRL website and
participate in the HSMM (high speed multimedia) working group. The
HSMM group only deals with working on high speed data via Amateur
radio. This group is producing proposed rule making changes to be
submitted to the FCC that would make operating simpler and allow more
reasonable usage of for example encryption. The author of this
document, Dave Anderson is a licensed amateur radio operator (KG4YZY)
and is on the ARRL HSMM Working group and a founding member of ARBA,
the Amateur Radio Broadband Aliance.
Michael T Miller
WL7CSL
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