15-04-2024, 02:53 PM
(This post was last modified: 15-04-2024, 03:03 PM by Mike Watterson.)
Are you going by dish size? That might just relate to which satellite is being uplinked or TX (ODU) power, rather than Ka or Ku. It's safe to assume none are C band! :D
Any transatlantic links are probably by Earth station, thus an extra hop to get live TV here. I could get some USA feeds from mid Atlantic sats when I had a motorised dish.
More capacity on Ka band. The Geosynchronous Ka band sats use up to 70 spot beams, each a tiny fraction of the economic Ku size spot. So each frequency might be reused twenty times by one satellite. Also the higher frequency bands are bigger.
A dish might be Ka or Ku or C or all three. I've had a Ku ODU here for two-way, and eye balled Ka and Ku two way links. They look the same. There is even a special reflector that lets through Ka and reflects Ku (or is it vice versa?) so two LNBFs or ODUs can be mounted on one arm for Ka & Ku at the same satellite.
I've 4 x Quattro Ku LNBFs and one Ka (2 port as it's just H & V, not dual band) LNBF into a multiswitch. Though Wikipedia claims Ka is 26 GHz to 40 GHz, most Satellite Ka in last 15 years is about 19 GHz to 21 Ghz for downlink and maybe 28 to 31 GHz for uplink. The Ku is what Sky & Freesat use and is 10.7GHz to 12.1 GHz approximately. It's a 1.1 m or 1.2 m dish with a curved mount on the arm for LNBs from 9E to 28.2E. You need a bigger dish as off axis gain is poorer. So dish points at 16E to give best gain for 13E and 19E LNBFs either side of the arm.
On Sky 28.2E the Irish TV channels use Sky encryption, on Ku band. But on 9E, the Irish TV channels (except Virgin/UPC) are FTA, on Ka band because the frequency reuse and narrow spots make reception in most of GB impracticable or impossible.
₣rom 2010. Same colour spot is the same frequencies. There are several Ka birds for ConUS.
This is a Ka band ODU. The slim bit at top back is an LNB for receive. The heatsink bit underneath is a 5W Ka band transmitter.
Transmit and receive use different bands (Uplink / downlink) and polarisation.
Here is a diagram of how the frequency reuse causes zones where the spot can't be received no matter how big the dish is:
Ka-Sat that I'm receiving Irish TV & Radio on right now, proposed bands in 2010.
The ODUs and LNBFs look the same for Ku and Ka.
The spot beams are lower power than Sky/Freesat, so while 45cm dish works in London for 28.2E Ku (Sky/Freesat and it's 65 cm here as we are closer to the edge of the beam), 90cm is recommended here for 9E Ka, even though the gain vs frequency means for C band you need twice as big a dish and Ka band half as big a dish (diameter), but only if the signal was the same!
Hence a minimum C band dish is about 2m and since it's lower frequency larger holes than Sky dish will work. A 3m mesh dish is good.
A solid 90cm Ku band dish will work for Ka, but a Sky type dish, even if 90cm is too poor due to the perforations. It hardly affects wind load. Cheaper to press to shape and cheaper to ship, but more prone to rust. A 60cm Ku band dish will work fine on Ka band till it rains!
I had to give back the 2 way stuff in 2008.
I modified a Cassegrain enclosed sat dish for terrestrial microwave use and it was used for nearly 15 years for my internet to make a 9km max system work at 13 km.
When I worked at the BBC the OB had to have line of sight to a TV mast. Terrestrial microwave links used and the dish on top of the OB truck pointed at the TV mast.
Any transatlantic links are probably by Earth station, thus an extra hop to get live TV here. I could get some USA feeds from mid Atlantic sats when I had a motorised dish.
More capacity on Ka band. The Geosynchronous Ka band sats use up to 70 spot beams, each a tiny fraction of the economic Ku size spot. So each frequency might be reused twenty times by one satellite. Also the higher frequency bands are bigger.
A dish might be Ka or Ku or C or all three. I've had a Ku ODU here for two-way, and eye balled Ka and Ku two way links. They look the same. There is even a special reflector that lets through Ka and reflects Ku (or is it vice versa?) so two LNBFs or ODUs can be mounted on one arm for Ka & Ku at the same satellite.
I've 4 x Quattro Ku LNBFs and one Ka (2 port as it's just H & V, not dual band) LNBF into a multiswitch. Though Wikipedia claims Ka is 26 GHz to 40 GHz, most Satellite Ka in last 15 years is about 19 GHz to 21 Ghz for downlink and maybe 28 to 31 GHz for uplink. The Ku is what Sky & Freesat use and is 10.7GHz to 12.1 GHz approximately. It's a 1.1 m or 1.2 m dish with a curved mount on the arm for LNBs from 9E to 28.2E. You need a bigger dish as off axis gain is poorer. So dish points at 16E to give best gain for 13E and 19E LNBFs either side of the arm.
On Sky 28.2E the Irish TV channels use Sky encryption, on Ku band. But on 9E, the Irish TV channels (except Virgin/UPC) are FTA, on Ka band because the frequency reuse and narrow spots make reception in most of GB impracticable or impossible.
₣rom 2010. Same colour spot is the same frequencies. There are several Ka birds for ConUS.
This is a Ka band ODU. The slim bit at top back is an LNB for receive. The heatsink bit underneath is a 5W Ka band transmitter.
Transmit and receive use different bands (Uplink / downlink) and polarisation.
Here is a diagram of how the frequency reuse causes zones where the spot can't be received no matter how big the dish is:
Ka-Sat that I'm receiving Irish TV & Radio on right now, proposed bands in 2010.
The ODUs and LNBFs look the same for Ku and Ka.
The spot beams are lower power than Sky/Freesat, so while 45cm dish works in London for 28.2E Ku (Sky/Freesat and it's 65 cm here as we are closer to the edge of the beam), 90cm is recommended here for 9E Ka, even though the gain vs frequency means for C band you need twice as big a dish and Ka band half as big a dish (diameter), but only if the signal was the same!
Hence a minimum C band dish is about 2m and since it's lower frequency larger holes than Sky dish will work. A 3m mesh dish is good.
A solid 90cm Ku band dish will work for Ka, but a Sky type dish, even if 90cm is too poor due to the perforations. It hardly affects wind load. Cheaper to press to shape and cheaper to ship, but more prone to rust. A 60cm Ku band dish will work fine on Ka band till it rains!
I had to give back the 2 way stuff in 2008.
I modified a Cassegrain enclosed sat dish for terrestrial microwave use and it was used for nearly 15 years for my internet to make a 9km max system work at 13 km.
When I worked at the BBC the OB had to have line of sight to a TV mast. Terrestrial microwave links used and the dish on top of the OB truck pointed at the TV mast.
