Sec.  74.794   Digital emissions.

   (a)(1) An applicant for a digital LPTV or TV translator station construction
   permit  shall  specify that the station will be constructed to confine
   out-of-channel emissions within one of the following emission masks: simple
   or stringent.

   (2) The power level of emissions on frequencies outside the authorized
   channel of operation must be attenuated no less than following amounts below
   the average transmitted power within the authorized 6 MHz channel. In the
   mask specifications listed in  Sec. 74.794(a)(2) and (a)(3), A is the attenuation
   in  dB  and Δf is the frequency difference in MHz from the edge of the
   channel.

   (i) Simple mask. At the channel edges, emissions must be attenuated no less
   than  46 dB. More than 6 MHz from the channel edges, emissions must be
   attenuated no less than 71 dB. At any frequency between 0 and 6 MHz from the
   channel  edges,  emissions  must  be attenuated no less than the value
   determined by the following formula:

   A (dB) = 46 + (Δf^2 /1.44)

   (ii) Stringent mask. In the first 500 kHz from the channel edges, emissions
   must be attenuated no less than 47 dB. More than 3 MHz from the channel
   edges, emissions must be attenuated no less than 76 dB. At any frequency
   between 0.5 and 3 MHz from the channel edges, emissions must be attenuated
   no less than the value determined by the following formula:

   A(dB) = 47 + 11.5 (Δf–0.5)

   (3) The attenuation values for the simple and stringent emission masks are
   based on a measurement bandwidth of 500 kHz. Other measurement bandwidths
   may be used and converted to the reference 500 kHz value by the following
   formula:

   A(dB) = A[alternate]+ 10 log (BW[alternate]/ 500)

   where  A(dB)  is  the measured or calculated attenuation value for the
   reference 500 kHz bandwidth, and A[alternate]is the measured or calculated
   attenuation for a bandwidth BW[alternate]. Emissions include sidebands,
   spurious emissions and radio harmonics. Attenuation is to be measured at the
   output terminals of the transmitter (including any filters that may be
   employed).  In  the  event  of  interference  caused to any service by
   out-of-channel emissions, greater attenuation may be required.

   (b) In addition to meeting the emission attenuation requirements of the
   simple  or  stringent  mask  (including attenuation of radio frequency
   harmonics), digital low power TV and TV translator stations authorized to
   operate  on  TV channels 22–24, (518–536 MHz), 32–36 (578–608 MHz), 38
   (614–620 MHz), and 65–69 (776–806 MHz) must provide specific “out of band”
   protection  to  Radio  Navigation  Satellite Services in the bands: L5
   (1164–1215 MHz); L2 (1215–1240 MHz) and L1 (1559–1610 MHz).

   (1) An FCC-certificated transmitter specifically certified for use on one or
   more of the above channels must include filtering with an attenuation of not
   less than 85 dB in the GPS bands, which will have the effect of reducing
   harmonics in the GPS bands from what is produced by the digital transmitter,
   and this attenuation must be demonstrated as part of the certification
   application to the Commission.

   (2)  For  an  installation on one of the above channels with a digital
   transmitter not specifically FCC-certificated for the channel, a low pass
   filter or equivalent device rated by its manufacturer to have an attenuation
   of at least 85 dB in the GPS bands, which will have the effect of reducing
   harmonics in the GPS bands from what is produced by the digital transmitter,
   and must be installed in a manner that will prevent the harmonic emission
   content from reaching the antenna. A description of the low pass filter or
   equivalent device with the manufacturer's rating or a report of measurements
   by a qualified individual shall be retained with the station license. Field
   measurements of the second or third harmonic output of a transmitter so
   equipped are not required.

   [ 69 FR 69336 , Nov. 29, 2004]