# Presentation: 668013

## CBA 2004

- CBA 2004

- _[KEITH.LARSON@fcc.gov](mailto:KEITH.LARSON@fcc.gov)__  FCC Media Bureau           (202) 418-2607_

**Notes:**
Hello Broadcasters
Hello Community Broadcasters
Pleasure to be here – thanks
Will all broadcasters stand and be recognized
Exciting time – much to talk about

##           GOOD  MORNING ! 

## Today’s Topic: Technical Aspects of Digital LPTV Report and Order

- Protected Contours & Power Limits
- Interference Protection
- Out-of-Channel Emissions
- Transmitter Certification
- Modification of Equipment

## Digital Protected Signal Contours and Current ERP Limits

| Channels | Protected Contour | Effective Radiated Power |
| --- | --- | --- |
| 2-6 | 43 dBu | 300 watts |
| 7-13 | 48 dBu | 300 watts |
| 14-69 | 51 dBu | 15,000 watts |

## Signal Coverage

- UHF station:  300 feet above average terrain;  15,000 watts

- X

- 26 mi

- 51 dBu

- F(50,90) =

## Interference Protection

- Permits other means of interference avoidance to maximize channel availability

- Best prediction modeling for ensuring protection

- Fully account for terrain features and the RF environment

## Digital Station Interference Prediction Analysis

## D/U Signal Strength Ratios

-    For no predicted interference:
-    D  -  U  >= Interference Threshold

- Desired Signal Strength (D)

- Undesired Signal Strength (U)

- D and U are expressed in field strength units of dBu (decibels above 1 microvolt per meter)

- D – U expressed in decibels

## Adopted D/U Interference Thresholds

- D/U values for different channel relationships between protected and potentially interfering stations
- Except for adjacent channel interference from digital stations, apply § 73.623(c) of DTV rules
- Examples for co-channel protection
- Digital protecting digital:      + 15  dB
- Digital protecting analog:      + 34  dB

## D/U Ratios for Interference From First Adjacent Channel Stations

| Emission Mask | DTV-into-Analog | DTV-into-DTV |
| --- | --- | --- |
| Simple |           10 dB |          - 7 dB |
| Stringent |             0 dB |          -12 dB |

## Contour Protection Methodology

**D - U >= Threshold value****?  Where U is the predicted strength of the proposed station.**

## Adopted Use of the DTV Prediction Methodology for Digital LPTV, TV Translator and Class A Stations

- OET Bulletin 69
- Longely-Rice Propagation

## Establish grid over protected contour

- FCC(50,90) = 51 dBu  (UHF digital LPTV)

- DTV Interference Prediction Method                 (Simplified illustration)

**Notes:**
For every radial get lat and long and look for bounding values.  Draw box and divide into 2 km cells.
If grid is 80 x 100 miles (129 x 161 km), then create 65 x 80cell grid with 5200cells.   

## Identify “Good” Cells:   Longley-Rice Field Strength of Desired Signal Exceeds Noise-limited Value (e.g., 41 dBu for UHF)

- +

- P

- L-R (50,90)P

- > 41 dBu

- =

## Check “Good” Cells for Interference (Longley-Rice)   

- *

- +

- +

- Signal Strength of Protected Station at Pth Cell ( D )

- Signal Strength of Potentially Interfering Station (U)

- P

- (D - U) > Threshold ?

## D/U Adjusted for Affects of Receiving Antenna Suppression 

- D/U = D/Uuncorrected  +  antenna suppression >= Threshold?

**Notes:**
Antenna receiver gain pattern shaped like bowling pin or old glass milk bottle.
Receiving antenna assumed pointed at DTV station.

## Determine Cell Populations             From Census Data

- Obtain service population by adding populations of “good” cells (i.e., signal above noise-limited value and no predicted interference)

## OET Bulletin 69 DTV Methodology Predicts Service Population

- Service Area (Population)

- X

- Proposed Station

- Bad Cells - “masking” interference from another station

- Bad Cells – signal is terrain-blocked

## Permitted Service Population Reductions

| Protected Station | Population Reduction Allowance |
| --- | --- |
| Full-service DTV | 0.5 % |
| Full-service TV | 0.5 % |
| Analog or digital Class A | 0.5 % |
| Analog or digital LPTV or TV translator | 2.0 % |

## Need to Tailor Assumed Vertical Antenna Pattern in Table 8. of OET 69 Model for Typical Antennas Used by LPTV Stations

-         Assumed vertical relative field =  0.110 for Φ >= 6  degrees

- ERPMAX = 10 kW

- ERP (6o =  121 watts)

- 6 o

- 1000 feet

- 10 miles

- Φ

- =

## Assumed Vertical Antenna Pattern

- As temporary measure, will double values in Table 8 of OET Bulletin 69 up to a value of 1.00
- FCC open to a revised procedure if more realistic assumed vertical field strength values are proposed

## Applicants for analog LPTV, TV translator or Class A stations may use either the contour overlap or OET Bulletin 69 DTV approach without need for a rule waiver  

## Other Available Means for Channel Finding

- Co-located adjacent channel operation

- Interference Agreements

## Transmission Issues

- Require FCC Certification of New Digital LPTV and TV Transmitters

## Key Transmitter Performance Criteria for Certification

- Produces output signal that can be satisfactorily viewed on receivers designed for FCC DTV transmission standard
- Does not exceed the maximum rated “digital average” power output under any condition
- Out-of-channel emissions at output terminals (including all output filtering) meet the attenuation requirements of the “simple” mask
- Local oscillator frequency of RF upconverter must be maintained within 10 kHz

## Emission Masks

- Total Average Channel Power

- 0.5 MHz

- -0.5 MHz

- 6 MHz

- - 6 MHz

- 6 MHz Channel

- 3

- 3

- 47 dB down

- 76 dB

- 76 dB

- 71 dB

- 71 dB

## Emission Resolution Bandwidth

- Standard bandwidth of 500 kHz
- Results from any alternate bandwidth should be converted to equivalent results from 500 kHz bandwidth:
-   A (dB) = Aalternative + 10 log (BWalternative /500)

## GPS Protection From 2nd and 3rd Harmonic Emissions

- RNSS frequency bands:  1164-1215 MHz, 1215-1240 MHz and 1559-1610 MHz
- Affects only TV channels 22-24, 32-36, 38, and 65-69
- For FCC certification, transmitter must employ filtering that attenuates harmonic emissions in the RNSS bands by at least 85 dB

## GPS Protection From 2nd and 3rd Harmonic Emissions

- External filter with at least 85 dB attenuation in the RNSS bands may be field-installed on an existing transmitter
- Field measurements of the second or third harmonic output of transmitters so equipped are not required

## Modification of Transmission Systems

- Permit modification of existing analog equipment for digital transmissions (*e.g.*, final RF amplifiers)
- FCC certificated manufacturer field modification kits
- Custom modifications

## Modification of Transmission Systems

- For custom modifications, transmitter must be performance-tested and station licensee must certify compliance with transmitter certification requirements

## To obtain FCC documents go to www.fcc.gov 
For digital translator/LPTV Notice of Proposed Rule Making (NPRM)
On the FCC home page click <Bureaus and Offices> and then <Media>
Scroll to headlines for 10/03/03 and click on link for the NPRM

- For digital translator/LPTV Notice of Proposed Rule Making (NPRM)
- On the FCC home page click <Bureaus and Offices> and then <Media>
- Scroll to headlines for 10/03/03 and click on link for the NPRM

## Thanks!                             Questions?

- Thanks!                             Questions?

## CBA 2004

- CBA 2004

- _[KEITH.LARSON@fcc.gov](mailto:KEITH.LARSON@fcc.gov)__  FCC Media Bureau           (202) 418-2607_

**Notes:**
Hello Broadcasters
Hello Community Broadcasters
Pleasure to be here – thanks
Will all broadcasters stand and be recognized
Exciting time – much to talk about

## Use of Carrier Frequency Offset by Analog Stations 

- fv

## Frequency Offset Operation

- Co-channel D/U ratio of 45 dB where analog stations operate without 10 kHz offsets or on same offset
- Ratio of 28 dB between stations operating on different offsets (a huge difference)

## Effect of Offset Relationship 

- 10 kW/500 ft co-channel stations

- Protected Signal Contour

- 102 mi

- Interfering Signal Contour without offset

- x

- With offset

## New Offset Policy – Consider the Following Situation

-    A proposed analog station fails to protect an existing co-channel LPTV or translator stations operating without a frequency offset
-    If the proposed station could protect the existing station if both operated with different offsets, then:
-    FCC would direct the existing station, at its expense, to operate with a frequency offset

## Check Each Good Cell for “raw” Interference

- *

- +

- +

- Desired Station DTV ( D )

- Interfering Station (U)

- P

- U:   L-R (50,10)

- D:  L-R (50, 90)

- (D - U)raw > Threshold Standard?

**Notes:**
Cull NTSC stations for analog into digital study.  For example, all co-channel NTSC stations within 300 km studied. 

## Cell Interference Accounting for Receiving Antenna Suppression 

- Interfering Station (U)

- g antenna = cos (

- F/B  = lesser of                     - 20 log (g)   or 14 dB

- D/U = D/Uraw +  F/B

**Notes:**
Antenna receiver gain pattern shaped like bowling pin or old glass milk bottle.
Receiving antenna assumed pointed at DTV station.

## OET Bulletin 69 DTV Prediction Methodology Protects Service Population

- Service Area (Population)

- X

- Proposed Station

- Protected Station

- Bad Cells- Interference from another source

- Bad Cells – No service, signal is terrain-blocked

- Proposed Station Cannot Reduce Service Population by more than 0.5%

## DTV Service Area

- shadowed

- NTSC IX

- DTV IX

- NTSC + DTV IX

- DTV Service

## Modification of Transmission Systems

- Digital output power may not exceed 25% of previous peak sync NTSC output power
- For custom modifications, transmitter must be performance-tested and station licensee must certify compliance with transmitter certification requirements

## Digital Low Power TV and TV Translator Rules and Policies

- IEEE Broadcast Symposium  September 13, 2004

##           Digital LPTV and TV Translator Rules   

- Keith Larson         Media Bureau, FCC            (202) 418-2607     Keith.Larson @fcc.gov