RE: [amsat-bb] Primestar

[Mike Gilchrist <kf4fdj@xxxxxxxxx>]

Bob,
At 10:54 AM 12/13/99 -0500, Bob Bruninga wrote:

>Are there some part15 rules that allow license-free microwatt emissions or
>whatever on these frequency bands?  With the gain of these dishes, even a
>few microwatts could make a usable pt-to-pt link.  Also with the 1 degree
>beamwidth, the chance of interferring with anyone else is near zero...?
>
>Now, how to generate a stable few microwatts at 12 GHz!
>
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12 GHz transmissions are not allowed for the purpose you ask as near as I 
can determine.

However, the FCC has allocated unlicensed transmissions, for PTP microwave 
on certain bands.  Here are the references:

Section 15.321  Specific requirements for asynchronous devices operating in 
the 1910-1920MHz and 2390-2400 MHz bands.

Section 15.321  Specific requirements for asynchronous devices operating in the
                 1910-1920MHz and 2390-2400 MHz bands.

         (a)  Operation shall be contained within either or both the 
1910-1920 MHz and 2390-2400 MHz bands.  The emission bandwidth of any 
intentional radiator operating in these bands shall be no less than 500kHz.

         (b)  All systems of less than 2.5MHz emission bandwidth shall 
start searching for an available spectrum window within 3 MHz of the band 
edge at 1910, 1920, 2390, or 2400 MHz while systems of more than 2.5MHz 
emission bandwidth will first occupy the center half of the band.  Devices 
with an emission bandwidth of less than 1.0MHz may not occupy the center 
half of the sub-band if other spectrum is available.

         (c)  Asynchronous devices must incorporate a mechanism for 
monitoring the spectrum that its transmission is intended to occupy.  The 
following criteria must be met:

                 (1)  Immediately prior to initiating a transmission, 
devices must monitor the spectrum window they intend to use for at least 50 
microseconds.

                 (2)  The monitoring threshold must not be more than 32dB 
above the thermal noise power for a bandwidth equivalent to the emission 
bandwidth of the device.

                 (3)  If no signal above the threshold level is detected, a 
transmission burst may commence in the monitored spectrum window.  Once a 
transmission burst has started, an individual device or a group of 
cooperating devices is not required to monitor the spectrum window provided 
the intraburst gap timing requirement specified below is not exceeded.

                 (4)  After completion of a transmission, an individual 
device or cooperating group of devices must cease transmission and wait a 
deference time randomly chosen from a uniform random distribution ranging 
from 50 to 750 microseconds, after which time an attempt to access the band 
again may be initiated.  For each occasion that an access attempt fails 
after the initial inter-burst interval, the range of the deference time 
chosen shall double until an upper limit of 12 milliseconds is 
reached.  The deference time remains at the upper limit of 12 milliseconds 
until an access attempt is successful.  The deference time is 
re-initialized after each successful access attempt.

                 (5)  The monitoring system bandwidth must be equal to or 
greater than the emission bandwidth of the intended transmission and shall 
have a maximum reaction time less than 50xSQRT(1.25/emission bandwidth in 
MHz) microseconds for signals at the applicable threshold level but shall 
not be required to be less than 50microseconds.  If a signal is detected 
that is 6dB or more above the threshold level, the maximum reaction time 
shall be 35xSQRT(1.25/emission bandwidth in MHz) microseconds but shall not 
be required to be less than 35microseconds.

                 (6)  The monitoring system shall use the same antenna used 
for transmission, or an antenna that yields equivalent reception at that 
location.

                 (7)  Devices that have a power output lower than the 
maximum permitted under the rules may increase their detection threshold by 
onedecibel for each onedecibel that the transmitter power is below the 
maximum permitted.

         (d)  Emissions shall be attenuated below a reference power of 112 
milliwatts as follows: 30 dB between the subband edges and 1.25 MHz above 
or below the subband; 50dB between 1.25 and 2.5MHz above or below the 
subband; and 60 dB at 2.5 MHz or greater above or below the 
subband.  Compliance with the emissions limits is based on the use of 
measurement instrumentation employing a peak detector function with an 
instrument resolution bandwidth approximately equal to 1.0percent of the 
emission bandwidth of the device under measurement.

         (e)  The frequency stability of the carrier frequency of 
intentional radiators operating in this section shall be ±10ppm over 10 
milliseconds or the interval between channel access monitoring, whichever 
is shorter.  The frequency stability shall be maintained over a temperature 
variation of -20o to +50o Celsius at normal supply voltage, and over a 
variation in the primary supply voltage of 85 percent to 115 percent of the 
rated supply voltage at a temperature of 20 degrees Celsius.  For equipment 
that is capable of operating only from a battery, the frequency stability 
tests shall be performed using a new battery without any further 
requirement to vary supply voltage.

         (f)  An asynchronous transmission burst is a series of 
transmissions from one or more transmitters acting cooperatively.  The 
transmission burst duration from one device or group of devices acting 
cooperatively shall be no greater than 10milliseconds.  Any intraburst gap 
between cooperating devices shall not exceed 25microseconds.

         (g)  Operation of devices in the 2390-2400 MHz band from aircraft 
while airborne is prohibited, in order to protect space research operations 
at the National Astronomy and Ionospheric Center at Arecibo, Puerto Rico.






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