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Here's the document, if it will go through.
73, Zack W9SZ
On Thu, Oct 7, 2021 at 8:05 AM Rus Healy, K2UA <Rus.healy@...
K9PW took data on this and found that the lens adds 13 dB to the horn.
He also plotted the gain versus spacing on the same range and found that the best spacing is 3.7 to 3.9 inches from the horn aperture to the lens frame. (It would be about 0.1 inch farther to the lens itself.) The spacing is relatively noncritical to the gain increase.
I have tested this setup, with a second unit, and can confirm that the signal increase is at least 10 dB with the lens in place.
On Thu, Oct 7, 2021 at 9:02 AM Steve Gemeny <steve@...
The combination of lens and horn is intriguing to me but comes with some questions:
- Have you any idea the gain of the two; I’m just guessing but maybe 3-6 dB over the horn alone, but a more informed estimate might be nice to know.
- It’d be nice to see a configuration sketch, and/or photo. The 150mm FL is easy enough to work from, but that’s from the phase center of the feed which is not usually known; Is the assumed ~30% into the horn good enough or is it just found by experimentation with the lens placement? A measured distance from feed face to lens on a well aligned system might be a better start.
This is an interesting configuration and one I am likely to tinker with so actual “user commentary” would be of great value to me (and maybe others).
Steve - AA3NM
3212 Patapsco Rd..
Finksburg, MD 21048
301-UN 4-4208 (If I’m home)
For one thing, a 12 inch dish at 122 GHz has a beamwidth of 0.56 degrees. A 24 inch dish has a beamwidth of 0.28 degrees. My skills at aiming a dish aren't that good. The teflon lens has a beamwidth of maybe 5 degrees. A lot easier to point. If you're going for really long distances (> 25 km) you would probably want the dish. If you want to work someone closer than that, the 20 dB horn or the horn with lens works well.
What is the benefit of using a lens at 122GHz over a dish?
It sounds like an intriguing option.
Warren - WF0T