Dual Band Feed

  • If anyone is interested, I have been adapting the antenna in two ways, firstly to add a "pie tin" choke ring as suggested by Willi HB9PZK to improve the radiation pattern and secondly a 2.2/8.4 GHz version that might be useful for detecting deep space satellites. This is a rather specialist application, trying to see if you can detect a satellite 100s of millions of km away. Easy with a 35m or 70m dish, not so easy from your back garden.

    The choke ring mainly makes a difference to the 2.4 GHz sidelobes. This is not significant enough benefit for QO100. It won't make the signals into the transponder much stronger; it would reduce interference to adjacent satellites, but there are none; it will improve the performance on 2.4 GHz receive, but QO100 systems do not receive on 2.4 GHz. Conversely, the 2.2/8.4GHz feed is only for receive so it's worth adding this.

    The Twitter thread is here https://twitter.com/TheRealMike/status/1177286413685014528

  • You say the "pie tin" reduces side lobes at 2.4GHz would this mean reduced transmit outside the dish area, I am sandwiched on 3 sides by other houses rather close by, so the less 2.4GHz I throw towards the other houses the better. I am thinking forward to when I try DATV at higher power. I know I am just being cautious. What height is the ring and does it go on the outside of 105mm ie can it be fitted to an already made POTY.

  • OK Mike I will leave as it is. I am not wanting to mess with a good antenna and I reckon I am doing well with 0.75 Watts to a 1 metre dish on NB. So it will be a case of do not touch.

    I am sure mk2, mk3 etc feeds will follow eventually, if so I will make one at the time, all that information not a lot to me i will have to understand smith charts first.:)