[NLRS] Yagi Spacing Q..

[jcplatt1 at mmm.com]

Hi Scott.  I'll take a stab at this.

What you are talking about is "stacking" yagi's for different frequencies
on one mast, not stacking similar yagi's for one band on one mast for
additional gain.    Many of us do this simply because we have one tower and
one mast.

There is a good application note on this subject on the Directive Systems
web site.   Go to http://www.directivesystems.com/ and click on "APP Notes"
on the left side, then in the list of application notes that appears find
the one titled "HOW TO PLAN THE INSTALLATION OF MULTIPLE VHF ANTENNAS ON
ONE MAST".    This says it all.

For short boom yagis like you have, you can get them fairly close .... but
there is no magic number.  Typically the lower band antenna (2m) doesn't
even "see" the higher band (440) antenna, its the higher band antenna that
suffers gain and pattern degradation from being too close.  In other words,
your 2m antenna will be just fine, but the 440 antenna should be spaced
some distance away.  With these small boom lengths, I would speculate that
you could go as close at 24", but that 36" is better.  I will stick my neck
out a bit further and say that you will not notice any improvements with
spacing greater than 36", although it will not hurt.    If you are using
longer boom yagis more spacing would be needed (see the reference app
note).

73, Jon
W0ZQ