A video introduction to the dish antenna, something that will become a major part of this series going forward. Links: My website and other social media - sgcderek.githu... PhyDemo ray optics sim - phydemo.app/ra...
Back in the early 70's my neighbor and I built a ground station for the SMS-1 weather geostationary satellite operating on 1691 MHz. We used a surplus 10 ft. parabolic dish from a LOS microwave link, we used a gridwald 1691 MHz down converter to down convert the signal from 1691 MHz to 137.5 MHz and our feed horn was a 2 lb coffee can open on one end with a 1/4 wave copper stub (the antenna) protruding through the side of the can 1/4 wave from the back of the can. The signal from the down converter was fed to the antenna input of an FM receiver on 137.5 MHz with the RF filters removed. The audio from the FM receiver was feed into a wet paper fax machine .The system worked outstanding and we got loads of images from it.
Another point that should be brought up in your expiation of how the feed can be moved across the surface of the dish as long as it stays at the focal point of the reflector, is this. If you could measure the combined distance from the opening of the feed horn to any point the surface of the reflector to the satellite in space the distances would all be the same within the surface tolerances of the reflector to keep all of the received energy in phase. Another good point to remember is that a reflector with an offset feed is just a portion of a prime focus reflector that has the highest gain for the diameter. You can see this if you shine a flashlight onto the surface of a prime focus reflector at an angle and only illuminate part of the reflector you will see that the flashlight produces an elliptical pattern on the surface of the reflector that looks just like that of an offset reflector.
I wonder why ku band tends to use offset dishes, could it be that the small size dish means a larger proportion of its area would be occupied by the feed. So using offset makes more sense.
That is definitely a part of it. It is also much simpler (and mainly cheaper) to manufacture the single arm design of an offset dish, which wouldn't be very practical with prime focus antennas.
![[LIVE] MCHOICE & MINT AWARDS 2024 at TRUE ICON HALL, ICONSIAM](http://i.ytimg.com/vi/wMewUeT5nbY/mqdefault.jpg)
Not boring at all. Very informative. Thanks!
The flashlight demonstration was fantastic. Thank you!
Cool introduction to dishes! Also not boring at all,
I'm not bored at all, and look forward to more, I also have an old sat tv dish and can't wait to see what I might be able to do with it.
Back in the early 70's my neighbor and I built a ground station for the SMS-1 weather geostationary satellite operating on 1691 MHz. We used a surplus 10 ft. parabolic dish from a LOS microwave link, we used a gridwald 1691 MHz down converter to down convert the signal from 1691 MHz to 137.5 MHz and our feed horn was a 2 lb coffee can open on one end with a 1/4 wave copper stub (the antenna) protruding through the side of the can 1/4 wave from the back of the can. The signal from the down converter was fed to the antenna input of an FM receiver on 137.5 MHz with the RF filters removed. The audio from the FM receiver was feed into a wet paper fax machine .The system worked outstanding and we got loads of images from it.
That sounds really cool, do you happen to still have some of the images?
@@dereksgc No I don't that was around 48 years ago all I have the great memories.
Thanks. I was looking for a video about dish antennas.
Video is to the point and very informative
Very Informative. Thanks!
thank you for this video! great info!
Another point that should be brought up in your expiation of how the feed can be moved across the surface of the dish as long as it stays at the focal point of the reflector, is this. If you could measure the combined distance from the opening of the feed horn to any point the surface of the reflector to the satellite in space the distances would all be the same within the surface tolerances of the reflector to keep all of the received energy in phase.
Another good point to remember is that a reflector with an offset feed is just a portion of a prime focus reflector that has the highest gain for the diameter. You can see this if you shine a flashlight onto the surface of a prime focus reflector at an angle and only illuminate part of the reflector you will see that the flashlight produces an elliptical pattern on the surface of the reflector that looks just like that of an offset reflector.
TY .. very informative
Cool Channel, love it.....
Hello I think in the sketches you confused the amplitude with the wavelength (you show the wavelenght as an amplitude)
Same thoughts
Question - Where on the feed antenna should the focal point of the dish hit? (I assume it is different for horn vs helical)
I wonder why ku band tends to use offset dishes, could it be that the small size dish means a larger proportion of its area would be occupied by the feed. So using offset makes more sense.
That is definitely a part of it. It is also much simpler (and mainly cheaper) to manufacture the single arm design of an offset dish, which wouldn't be very practical with prime focus antennas.
Thank you
on last slide satellite became death star 🤣
boring? i dont think anyone thinks that