THE HAPPY SATELLITE NERD EPISODE 94
Is the Sky Falling for C Band, again? There is solutions to 5G interference and we discuss that!
#stop5g #5G #5GKILLS
“Our sponsor Tek2000.com has asked me to post this because people on other forums without an understanding of basic physics and antenna theory are posting nonsense about the end of C-band satellite due to 5G.
Satellite AMC-11 at 131°W is being retired and American program suppliers are moving their content to 101°W. Satellite 135°W was retired last year and it appears 133°W, 127°W and possibly 125°W will be retired in the years ahead when they run out of fuel. I doubt they will be replaced.
In case you haven’t noticed, the American program suppliers are migrating everything to orbital slots between 91°W – 107.3°W, with SES-1, SES-3 and SES-11 being filled to capacity. :thumbsup They are doing this presumably to mitigate any interference issues that may arise from the launch of 5G wireless in 2020 and beyond. The theory behind this move is that the larger the look angle of the ground antenna, the lower the potential for terrestrial interference. This is because in addition to a primary lobe that is aimed at the satellite signal, antennas also have side lobes that pickup off-boresight terrestrial noise. Fortunately, these side lobes have gains that are -10dB, -20dB, -30db and -40dB down from the main lobe (every -3dB means half the gain). It also means that the higher in the sky the antenna is pointed, the less likely it is for terrestrial interference to enter the 2nd, or 3rd lobes and might only enter the 4th, 5th and other lobes which have extremely small gains and won’t interfere with the satellite signals. If the ground antenna has a small look angle, it is possible for terrestrial interference to enter the 2nd or 3rd lobes and give it sufficient gain to lower the SNR of the satellite signal and cause problems. In this case, some sort of filter or TI shielding will be required.
For those of you who have a ku LNB on a large dish (e.g. 12ft), you have probably already encountered the 2nd lobe when you hit a ku satellite and can just barely lock it. After you drive your dish just a bit east/west, the ku signal gain jumps dramatically as you hit the main lobe. This also occurs with C-band, but you need a much larger dish to observer it (e.g. 16ft or greater). If you have ever experienced this, then you will understand how terrestrial interference enters your dish.
So now that we understand the physics of side lobes and the potential for interference, let’s investigate antenna look angles.
1. In general, the closer your are to the equator, the larger your look angle. :thumbsup
Look Angle = 90° – Latitude
2. The closer you are to longitude 101°W, the larger look angle you will have when tracking 91°W – 107.3°W. :thumbsup
3. The further north or further east/west of longitude 101°W you are, the smaller the look angle. :thumbsdown
One more thing we need to emphasize. Larger antennas have smaller side lobes relative to the main lobe. Therefore, the potential for any kind of interference is reduced when a larger antenna is used, all other things being the same.
The map below shows all this pictorially and recommends the C-band antenna size you should select if you are just getting started in this hobby. It is worth noting, that after these satellite changes (i.e. moving most programming to around 101°W), ground noise interference (same theory applies) will also be reduced for most ground stations, which means, in theory, C-band satellite TV reception for most will be BETTER when 5G becomes common place. And faster channel changes and less wear-and-tear for your actuators too!”
SIT BACK AND BINGE ON A PLAYLIST OF VIDEOS