Stacks and SWR

Jay Terleski
Wed, 12 Feb 1997 09:14:04 -0600

L. B. Cebik wrote:
> Some beam stackers have experienced a rise in SWR if the beams are pointed in
> opposite directions.  Others have not.  The degree of SWR rise was not
> specified.
> To shed some light on this question, I ran a pair of identical beams through
> NEC-4.  The individual beams, cut to be resonant at 14.175 MHz had the
> following free space properties:
> TO angle      Gain (dBi)     F-B ratio (dB)     Beamwidth      Feed Z
>  (degrees)                                       (degrees)      (R+/jX)
>   ---           8.1           26.6                62            25.5 - 0.1

Good stuff, it seems to verify what I see with my three high stack of
4/4/4 on 10-20m  and my 2/2 on 40m.

BUT....Where in heavens name do y0ou get a 20m beam with 26.6 dbi gain
and 62 db F/B?  Not very real world.  I think you probably shrunk a UHF
antenna.  At best a long beam like that would have worse case mutual
coupling vs our small .5 to .75 WaveLength booms.  HI.  So its still a
valid run.  

Maybe I'm interpreting your data wrong?

Thanks for sharing this.  My NEC 2 stuff also verifies these trends of
numbers on the smaller beams I use. 

Jay, WX0B

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