Radome to active element separation

[JulianF]

Could any point me towards some guidelines for separation between active elements of UHF antennas (helix, yagi etc) and their radome? I was assuming half wavelength but I could do with coming in closer. Thanks.

 

[MacGyverS2000]

This might prove useful...

http://www.rfbeam.ch/fileadmin/downloads/appnotes/AN-03-Radome.pdf

Dan - Owner

http://www.Hi-TecDesigns.com

 

[VEBill]

Yagi and Helix antennas, including UHF, are most often installed outside without any radome.

Of course, your application may be different than the usual.

 

[khiggler]

I did have a log periodic detune and change gain by 4 dB (around 500 Mhz) when I contacted it to foam. i.e HH to VV antenna chamber test calibration, VV changed alot when I stuck it into the foam which it was placed atop.
Hence if your radome is going to touch a resonant antenna (narrow band, or log periodic or Yagi), then it will shift it down in frequency, even if the radome is entirely foam, and hence you'll need to adjust your elements making them shorter to retune it.
If the radome does not touch the antenna, you can probably locate it maybe 1/2 inch away.