[Towertalk] Element Interactions

[n4kg@juno.com]

While designing a 2L reflector Yagi for 6M, I played with the reflector
dimensions, going from 0.2 WL to 5.0 WL at a spacing of 0.15 WL.

I made two very interesting discoveries:

1 - parasitic lengths LESS than 0.3 WL are nearly 'INVISIBLE'.

2 - parasitic lengths MORE than 0.5 WL produce decreasing
     gain and F/B but NEVER become 'invisible', truncating
     at 2 dB gain and F/B of 4 dB with 0.15 WL spacing.

     This corresponds to 10.5 ft spacing on 20M, 7 ft spacing 
     on 15M, and 5.25 ft spacing on 10M.  I expect the effect
     would drop off (SLOWLY) as spacing is increased.	

     This suggests that any LOWER Frequency antenna WILL
     interact with any higher frequency antenna if they are in
     fairly close proximity (<0.5WL).

     Tom  N4KG

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