exactly Andreas, and that is why you normally optimize receive antennas for G/T or Gain over (system) noise temperature. Because this will end up in Signal-to-noise ratio.
Having a huge G with crappy T might be worse than decent G with low T. So depending on your setup, a slightly underilluminating feed will produce better results as it won't pick up as much noise from behind the main reflector (as for me, being close to the wall).
Alles schön und gut, erklärt aber immer noch nicht was an PE1CKK´s Tabelle falsch sein soll, die Andreas anzweifelt ?
Yep, that is exactly what I'm doing: some under illumination to prevent overspill to 'warm' areas because my setup is indoors.
Then concerning the 'gain' ( DL5CN doesn't believe this):
When you bundle an isotropic radiator into a 'beam' then you'll have 'gain', i.e. the energy will be radiated into a certain direction,
This of course is reciprocal, so your 'ears'/receiver will be more sensitive into that certain direction.
The dielectric lens does exactly this, it bundles the intrinsic radiation pattern from the open waveguide.
The measurements of several lenses (made by PE1CKK, NOT DF5VAE !) were performend with a HP435 Watt meter (see the tweet in on page 2 of this thread) and a 10368 MHz signal source several meters away. This signal was received and it's strength was measured with the (milli)Watt meter. The observed (-10 dB) opening angles and power (gain) is relative to the open waveguide <-- being 0 dB).
Ja, ich weiss - gibt es noch eine andere Lösung?
Sicher . . . : https://nl.aliexpress.com/item/32765040418.html <-- I use this LNB since March 2019 (I modified it to accept a 25 MHz reference)
