[TowerTalk] phasing antennas

[K4SB]

Jim Lux wrote:
> If one has a good antenna analyzer that reads both R and X, and you collect
> enough frequency points, you can calculate what a TDR would have given you.
> The Fourier transform is used to convert back and forth between time domain
> and frequency domain.
> 
> Looking  for dips in frequency domain is essentially a special case of this
> duality.  You're looking for places where the time delay for an impulse to
> propagate from one end to the other happens to be an exact multiple of one
> RF period.
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Good advice. Just a little addition. If you use an analyzer, use as
high a multiple of the frequency you want as possible. For example,
the MFJ is good to 170 mHz. For 50.1 or so, you'll get a much sharper
dip around 150 +.

And for heavens sake, always use a length of coax which is long enough
for both phasing lines. Velocity Factors vary widely, but rarely are
not the same in any one run of coax.

73
Ed