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clanon

Bifilar helix (backfire)

Starting point this site by Graham Sharples 

13 cm bifilar helix

I'd never found a good feed for DEEP DISHES ( i have a 1,26 m , 0.31 m deep dish F/d 0.25  )

bifilar helix_01.gif

Edited by clanon

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What's most important to me are the 180 degrees of illumination at about -6 db of gain...

helix length – 13cm, 1.5mm wire ,5 doble turns instead of 4 on original site

 -6dB beamwidth of around 180 deg (good for f/D ratios 0.25 (focal plane dishes) to 0.3)

-6dB in beamwidth corresponds  to a -10dB edge illumination (max gain) since there is an additional -4dB spreading loss to the edge at these low f/D ratios.

s11.JPG

vswr.JPG

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2.JPG

Adjusted at 2.437ghz center CH 6

can't run the parabolic dish, too big...i dunno how the dish would change this results...(yet)

Edited by clanon

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,,,why do not you try metal disk loaded helical antenna...???

307.jpg

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