> Thinking about a rotatable dipole for 75/80 meters.I could put it up at
> 85-90 feet.Worth the trouble at that height?I have Rohn 45 tower with
about
> 12 square feet of antenna load on it now (4 times 432-13wla).So I can't
get
> too crazy.Force 12,M2 what is the ideas out there.Will use it mostly to
> chase dx,as much as only 85 feet will do. Gregg K9KL
The answer depends on what you're using now and what your other
possibilities are. For some interesting reading on low-band antennas see:
www.w8ji.com/receiving.htm
www.w8ji.com/receiving_basics.htm
www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/RDFMetric.ht
m
As you'll note in the above material, receiving S/N ratio is more important
than gain and F/B ratios for receiving. And if you can't hear them, you
can't work them. Just for fun I compared a short rotatable dipole to an
inverted V with the apex at 85'. The rotatable dipole (RDF=3.8 at 20 degree
take-off angle) might see an improved S/N ratio on receive of 1 to 1.5 dB
over the inverted V (RDF=2.5 at 20 degrees), depending on the noise sources
in your area. Both antennas will have a maximum radiation angle or 45-55
degrees. Depending on your soil and available space (for radials), you
"might" get better performance from a vertical.
Clay W7CE
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