BASIC SATELLITE AND OUT OF FOOTPRINT RECEPTION

 By TBOY

Auckland, New Zealand

A question asked of the satellite professional very frequently is how big an antenna is required to receive a particular satellite or satellite service. This question covers both primary coverage areas and locations that are normally thousands of Kilometers out side the footprint coverage areas specified by the Satellite designers or operators.

This application can apply to both C and Ku band reception. However it is important to understand a little about satellite footprints including fringe area reception. Today's generation of satellites fall into several categories. The first consists of Communication Satellites such as Intelsat, Intersputnik and Pan Am Sat operate. These satellites are designed with the capability to serve global, Regional and domestic telecommunications requirements. The second are regional satellite systems such as Palapa, Apstar, and Asia Sat whose systems are designed around serving a series of regional countries markets. The third is Domestic satellite systems such as Optus, Astra and others designed to service a domestic telecommunications market.

Depending on the downlink configuration of the individual satellite, the receive earth station is dependent on the amount of signal generated throughout the footprint. Along with new innovations such as digital compression came various new transponder bandwidth configurations designed to provide cost effective distribution solutions. These transponder bandwidth allocations also account for the amount of signal to be found through out a specific footprint. Satellite operators will offer various bandwidth allocations on their transponders to accommodate their customer's specific requirements.

Using the Intelsat 701 satellite located at 180 degrees east as an example. A standard global beam is capable of generating 29 Dbw beam center to 26Dbw at the beam edge for a 36MHz full transponder bandwidth. This transponder bandwidth can be reduced from 36MHz to 18MHz (Half Transponder) to as low as 9 MHz for digital broadcast video distribution purposes. Along with these bandwidth reductions comes a reduction in signal strength or Effective Isotropic Radiated Power (EIRP) This is the same whether the downlink footprint is in Global, Hemispheric, Zone or Spot beam configuration. Whilst a full 36 MHz global beam transponder generating 29 Beam center to 26 Dbw EIRP beam edge can be well received on a receive antenna of between 3.2m to 5m.This receive system will provide a (Cnr) carrier to noise ratio of 10 Db.

If the global beam transponder is halved into two equal 18 MHz half transponders then our EIRP at the beam center now reduces by approximately 4 to 5 Db.The beam center Eirp reduces to 25Dbw and the beam edge Eirp to 21Dbw requiring dish sizes of between 5m and 9m respectively. For a 9MHz (SCPC) Single channel per carrier such as TVNZ uses on its global beam transponders worldwide the effective Eirp is reduced to 21.5Dbw beam center to a low of 18.5Dbw at the beam edge. This means to maintain our Carrier to noise ratio we now require a 9m receive antenna at the beam center and at least a 12m at the beam edge. When using digital compression techniques and a suitable system configuration digital compression can be used very effectively in lowering the required carrier to noise ratio needed to provide an effective reception solution.

By using Fec rates below R 3 / 4 a broadcaster such as TVNZ using Power restricted low bandwidth Single Channel Per Carrier (SCPC) Global footprint transmissions the Reception threshold point reduces to approximately 6 Db meaning that to effect reliable reception in the beam center 21.5Dbw contour our reception dish size only has to be 6m and 8m at the beam edge giving a overall saving of 3m to 4m. By using digital transmission techniques over analog the real saving is two fold with reduced threshold levels and up to four simultaneous SCPC broadcast quality channels can be fitted into the same transponder bandwidth as previously occupied a single channel or at best two half transponder channels requiring a larger reception antennas to provide broadcast grade reception.

The Satellite sports service SPN used to broadcast to the Pacific from it's studio's in Nauru only used 9 MHz of Intelsat Global bandwidth to broadcast an 8.02 Mbts broadcast quality signal. However SPN's channel was severely power restricted due to the small amount of bandwidth used. This service only required a 5m to 6m reception antennas in the beam center (Pacific Islands) and marginally larger dish sizes the closer to the beam edge the reception was required. Until the advent of Digital Compression this type of Broadcast service was unavailable requiring at least a full transponder's power level to work with dish sizes lower than 7m.

 

Example of Global Beam Coverage from 50 Degree and 142.5 degree Gorizont Satellites

 

Similarly Optus and Pan Am Sat can split Their 54 MHz Full transponders into two 27 MHz half transponders. Sky Television NZ has elected to split their 54 MHZ full transponders into two equal 27 MHz Half transponders this increases the amount of channels they can carry but reduces the available Eirp from 55Dbw beam center to 51 Dbw for a 27 MHz half transponder. This reduction in signal also increases the original receive dish size from an estimated 27cm at the beam center for full transponder operation to 45cm using half transponder operation in order to maintain the same carrier to noise ratio. Of course different locations require larger antennas than illustrated above. Auckland for example falls into the 4 9 Dbw contour which requires approximately a 55 cm to 60 cm size antenna to maintain stable reception for 99.9% signal availability.

 

 

Footprints courtesy Optus

So if certain satellites transponders appear to be weaker than others the chances are that the operator is not using the total power of the transponder and depending on the bandwidth allocated to a specific service the reception dish sizes could vary dramatically.

Most C band regional high power Zonal type beams such as Apstar, Asia Sat, Pas 2 / 8 and Thaicom produce beam center downlink EIRP's in excess of 37 Dbw when using a full transponder at full power. These signals are able to be well-received using 1.5 to 1.8m reception systems. Even at signal strengths of 30 Dbw broadcasters using a Fec rate of 3 / 4 producing an IRD threshold of 6Db, signals should be able to be resolved on systems under 2m The current transmissions from J C Sat 4 highlight this fact being able to be received on systems though out its primary coverage area on systems under 2.5m

Global beams used by Intelsat and Gorizont satellites have beam center EIRP's lower than 30 Dbw dropping to 25 / 26 Dbw beam edge. The dish sizes for broadcasts using Fec rate 3 /4 would be 3.5 to 4m in diameter.

Single Carrier per Channel broadcasts using a fraction of the total global beam (9MHz) bandwidth would require larger dish systems as the overall Eirp to the receiving dish will be very low resulting in the need for a much larger receiving system in the region of 5m to 7m in diameter.

High power Direct Broadcast Ku satellites carry only a few channels and are capable of providing EIRP's in the 55 to 60 Dbw regions; these can be resolved on dishes or flat plate antennas as small as 15 to 34 cm.

Pan Am Sats Pas 2 satellite's Australia / New Zealand beam using the full transponder bandwidth of 54 MHz is capable of producing 46 / 45 Dbw Eirp beam center in Australia and 45 / 44 beam center in New Zealand. Surprisingly enough a full saturated 54MHz transponder using Fec rate 3 / 4 can support at last 15 to 20 channels depending on the allocated bit rates and can be received on 60 cm to 76 cm .The footprint coverage area is so expanse it could be possible to receive overspill signals as far as Singapore and some of the Pacific Islands.

 

 

 

However by reducing the transponder bandwidth to a half transponder of 27 MHz we lose up to 4Db of signal making New Zealand's beam center EIRP now 41/40 Dbw. This requires at least a 1.5m dish to provide 10 Db carrier to noise ratio which would support a R 3 /4 digital carrier with an IRD threshold point of approximately 6 Db with a 3.5 Db rain fade margin for ITU region K as predicted for (New Zealand).

Depending on the Forward error correction values selected by the broadcasters the IRD threshold values can vary from just over 5 Db for R 1 / 2 to 6 Db for R 3 / 4 to 8 Db for R7/ 8 As a bench mark 6 to 8Db is approximately the minimum threshold point for analog FM satellite CNR’s. (The Fm Threshold point is where sparklies disappear and the picture becomes stable).

Footprint Pas 8 Australian Beam courtesy Pan Am Sat

Fringe area reception

There is no simple answer to this question as fringe area satellite reception can vary from location to location even from transponder to transponder. Normally the question is answered by some one conducting a detailed search at a specific location in the hope of obtaining a picture that is watchable. However there are certain operational criteria that are fundamental to all satellite transmissions. It is normal for the satellite designers to design the coverage area of footprint with a specific coverage area in mind.

The antenna on board the spacecraft's primary function is to provide a suitable signal to that specific service area. Before any antenna is integrated to the satellites bus its accuracy and performance is checked and measured on a test range and later tested again in orbit and measurements such as the (E IRP) Effective Isotropic Radiated Power at specific points within the coverage footprint.

All antennas produce Side lobes; these are smaller amounts of gain found either side of the main radiation lobe. It is very difficult to manufacture a perfect antenna so the theoretical design constraints of the transmit / receive antenna can provide a clue to where the position of its side lobes and nulls are on the earths surface. In real life side lobes and null positions are less predictable and the discovery of usable belts of signal depends on the physical location and size of the reception system.

Most fringe area satellite reception relies on a series of calculated guesstimates. In the case of Pas 8's Australian Ku beam the bore site Eirp is 52 Dbw. Normal beam bore siting accuracy is calculated to be in the region of plus or minus 0.2 degrees.

Our typical Transmit antenna consists of the main lobe with nulls either side followed by the first side lobe which peaks at about 14 to 22 DB lower than the main beam this could theoretically occur 5 or so degrees out from the bore site and could produce EIRP’s in the region of 34 + Dbw. This is followed by the second null where the signal levels drop to very small levels. The second side lobe is likely to occur 8 to 10 degrees from the bore site and could be several Db's lower again but could provide signal strengths in region of 24 to 28 Dbw, which could produce watch able signals on 5m to 7m antennas. Beyond the second side lobe the chances of receiving a resolvable signal are very slim.

  

Typical Satellite transmit Beam pattern

 

Satellite Dxing

Most of us living in Pacific Basin have read the American programming magazines and envied the sheer amount of channels available to dish owners living in the United States, hundreds of channels and down here in Australia, New Zealand and the Pacific we are thankful for the handful of channels provided free to air by Pas and Intelsat.

So is it feasible to receive signals from the American Domsats that squirt relatively high power C band signals the wrong way for dish owners in the South Pacific, the nearest we will get to American overspill signals is overspill from the Hawaiian spot beams.

And yes against all odds they have been received at least in New Zealand. It is fortunate that we do have line of site to most of the American domestic satellites. We used a 7m Orbitron Horizon to Horizon tracking antenna which was fitted with a 20 degree Lnb.giving us a G/T of about 27 DBK so it was nearly 6Db hotter than a common 3m domestic home system.

Please remember that these were all ANALOG C Band signals!

Satcom C1 @137 West. Produced 3 to 4 Db Cnr signals on most of the Clear transponders Vertical or horizontal were much the same in received signal.

Transponder 8 3860 V NBC Televisions Eastern feed to Affiliate Stations was perhaps the strongest signal followed by several FOX network Sports channels on transponders 9, 18 and 22. There were a few Video cipher feeds logged. 24 .3 degrees Elevation

Satcom C5 @135 West Transponder 5 3800 V Deutsche Welle was the strongest signal and was noted to be about 5Db Carrier to noise at least 3Db under threshold. Transponder 9 3880 v QVC the shopping channel was about the same signal strength, as was Transponder 11 3920 V Speed vision and transponder 19 4080v C Span. The horizontal transponders were weaker and were logged at 3Db Carrier to noise ratio.

Transponders 8 3860 H Preview Guide, 10 H 3900 HSC Home Shopping Club, Transponder 14 3980 H Cable Health Club were all logged at 3Db Carrier to noise ratio some 5 to 6 Db under threshold. 22.8 degrees Elevation

Galaxy 1R @133 West Produced several interesting Channels including several Religious channels and the Home and Garden Network on Transponder 20 4100 V and Value Vision Shopping network on transponder 12 V 3940 and the Nostalgia Channel on transponder 22 V 4140. Transponder 5 H 3800 produced the Arts classic Showcase but this was very poor and would have been under 3DB signal to noise 21 .2 degrees Elevation.

Satcom C3 @ 131West also produced some interesting channels the strongest was Court TV Transponder 6 H 3820, QVC 2 transponder 8 H 3860 and HSC2 transponder 10 H 3900, E Entertainment on Transponder 23 V 4160 was also noted but the verticals showed lesser signal strength. 19 .7 degrees Elevation

Galaxy 5 @ 125West again the horizontal transponders were stronger And several Religious channels were evident however the strongest transponder was 21H 4120 Knowledge TV with lesser quality on Transponder 20 V 4100 BET TV Black Entertainment TV. 15 degrees Elevation

Galaxy 9 @ 123 West Produced Such delights as ESPN News, Computer TV network, Showtime, and NHK. 13. 5 degrees Elevation

We could not look any lower as buildings were obscuring our line of sight. However we revisited all these satellites about 3 years ago with a Benjamin low Threshold extension Receiver that could be programmed to operate at levels approaching 3Db, the difference in Picture quality was amazing. Whilst the reception was nowhere near quality suitable for distribution it was quite acceptable for domestic use.

Other testing produced signals in the 3 to 4 Db carrier to noise ratio from most of the Asian satellites with elevations down to 2 degrees. The most impressive analog pictures coming from Chinasat 5 located at 115.5 degrees east producing 8 Pal channels. The strongest pictures came from Palapa B4 at 118and 108 degrees East Producing several Thai channels. However the most interesting finds were from the 103 degrees Gorizont producing near threshold pictures of APNA TV, Orbita 1 and the southern beam from Asia Sat 1 at 105 Degrees east which produced several Star TV channels including Prime Sports, Star TV, Channel V, EL TV, Pakistan TV, and Star TV Movies. Apstar at 138 degrees east produced several B- Mac channels as well as a near threshold feed of CNN. Much later a detailed look at Palapa C2 at 113 produced many of the hard to receive channels including ATV I, which also produced near threshold pictures with a minor bandwidth adjustment. Most of the channels viewed produced picture with CNR's in the 4Db region equating to EIRP’s of 12 to 15 Dbw. However a 10 to 12m-reception systems would be able to provide above threshold reception from these satellites, most which were designed, with footprints with zonal coverage of southern Asia.

Today things have changed and digital compression has made finding these exotic signals a lot harder due to the IRD having to reach its threshold point before producing a signal. However one thing must be remembered the IRD threshold point (IE) where the receiver produces a signal is governed by the Forward Error Correction rate and the transponder bandwidth. It so happens that American broadcasters seem to favor Fec rates of 3 / 4 providing us with an IRD threshold level of approximately 6db Carrier to noise. This is some 2 Db lower than required to produce Analog signals.

 

GALAXY 4 R @ 99 DEGREES WEST

Footprint Galaxy 4 R Conus / Hawaiian spot Beam courtesy Pan Am Sat

As can be seen by the above footprint courtesy of Pan Am Sat that the coverage to Hawaii from Galaxy 4R is via a dedicated Ku band spot beam. Located at 99 degrees east Galaxy 4 R provides more than encouraging hopes for reception in some of the pacific Islands. The Hawaiian spot beam center is 46 Dbw dropping to 42Dbw at the third contour.

By carefully calculating the reduction in EIRP as the footprint moves westward across the Pacific the beam center Eirp of 46 Dbw now reduces rapidly The first Major Island it hits is the Marshall group where it has lost some 18 Db of signal leaving the Marshall's with 28 Dbw of signal along with Kiribati, Tokelau and parts of French Polynesia. Still moving westward the Cook Islands, Western and American Samoa all fall within the region of 28 / 26 Dbw. Still moving westward Nauru, Tuvalu Niue, Tonga and Fiji share signals in the 22 to 24 Dbw regions while Guam and the Solomon's share 20 Dbw. Whilst this cannot be confirmed until somebody actually tries to obtain reception from Galaxy the above signal strengths would not be hard to find using the appropriate equipment See Eirp Vs Dish size table Below.

EIRP (Dbw)

C/N RATIO (Db) For Ku Systems

6

8

10

12

14

ANTENNA DIAMETERS (cm)

46

48

60

76

95

1.07

43

67

85

1.07

1.34

1.69

42

76

95

1.2

1.51

1.90

40

95

1.2

1.5

1.90

2.39

38

1.20

1.51

1.90

2.39

3.01

36

1.51

1.90

2.39

3.01

3.37

32

2.39

3.01

3.78

4.76

6.00

30

3.01

3.78

4.76

6.00

7.55

28

3.78

4.76

6.00

7.55

9.51

27

4.25

5.35

6.73

8.47

10.67

26

4.76

6.00

7.55

9.51

11.97

24

6.00

7.55

9.5

11.97

15.07

23

6.37

8.47

10.67

13.42

16.90

22

7.55

9.51

11.97

15.07

18.97

21

8.47

10.67

13.42

16.90

21.28

20

9.51

11.97

15.07

18.97

23.88

EIRP V DISH SIZE

GALAXY 4R

Firstly what is on Galaxy 4R that would be of interest to us? It's very simple on board Galaxy 4R @99 degrees west occupying twelve full transponders starting at:

Transponder 4 11780 V, 5 11800 H, 6 11820V, 7 11840 H, 9 11880 H, 10 11900 V, 11 11920 H, 12 11960 H, 17 12040 H, 18 1206 V, 22 12140 V, 23 12160 H.

These Twelve transponders carry the Cable programming channel selection for (HITS) which stands for HEAD END IN THE SKY.

Transponder 4 @ 11780 V Carries: The biography Channel, Trio, A+E History, Much Music, Toon Disney, MTV2, Nick Gas, Style, Lifetime Movie Channel.

Transponder 5 @ 11800 H Carries: America's Voice, ESPN PPV 1, 2, 3,4,5,6 ESPN NOW, ESPN EXTRA PPV.

Transponder 6 @ 11820 V Carries: ESPN 2, Discovery Home and Leisure, Speed Channel, Discovery Civilization, ESPN Alternate, and VH 1 Country, VH2 Classic, Discovery Wings. And Twenty one Radio stations.

Transponder 7 @ 11840 H Carries: HBO 2 West, HBO Signature West, Showtime 2 West, The Movie Channel, Starz! Theater West, Love Stories West, Mystery West, The History Channel, Bravo US, HGTV US, ESPN Classic.

Transponder 9 @ 11880 H Carries: HBO 2 East, HBO Signature East, Showtime 2 East,

The Movie Channel East, Starz! Theater East, Westerns East, Love Story's East, Mystery East, The History Channel East, Bravo US, HGTV US, ESPN Classic, 5 Radio Channels.

Transponder 10 @ 11900V Carries: IN Demand 1, IN Demand 2, IN Demand 3, IN Demand 4, IN Demand 5, IN Demand 6, Hot Network, TV Land, Sci Fi Channel, Out Door Life, Woman's Entertainment, and 5 Radio Channels.

Transponder 11 @11920 H Carries: Discovery Kids, The Science Channel, The Golf Channel, Discovery Health, ESP news, IFC US, The Game Show Network, Playboy TV, BBC America East, TCM, Noggin.

Transponder 12 @ 11960 H Carries: News World International, Black Starz East, Ovation The Arts Network, BET Action PPV, Spice 2, VH 1 Soul, The Box Edge, The International Channel, BET on Jazz, Sundance Channel West, 8 Radio channels.

Transponder 17 @ 12040 H Carries: True Stories East, Action East, Showtime East, Cinemax East, Movie Max East, HBO Family East, Encore East, Starz! East, Showtime Extreme East, The Movie Channel Extra East,

Transponder 18 @1206 V Carries: Action West, HBO West, Showtime West, Cinemax West, More Max West, HBO Family Network, Showtime Showcase West, Encore West, Starz! West, Showtime Extreme West, The Movie Channel Xtra West.

Transponder 22 @ 12140 V Carries: The Good life TV Network, Tech TV, Bloomberg TV US, Fox Movie Channel, Weather Scan, TBN Trinity Broadcasting, Outdoor Channel, Spice.

Transponder 23 @ 12160 H Carries: Great American Country, DIY Do It Yourself Network, The Comedy Network, Nue TV, MTV Spanish, MBC Network, The Word Network.

Galaxy 4R is the major satellite distribution platform for the US cable networks and as can be seen every type of channel is represented in East and West time zones. For Viewers outside Galaxy 4 R's coverage Area of the continental US and Hawaii if reception can be resolved it puts every channel on one platform, Whether the General instrument Digicypher 2 decoders or Authorization is available for reception of these channels is allowed is not the objective here. The prime objective was to prove or disprove the reception of Satellite Signals thousands of Kilometers out side of their designed coverage Area.