On Wed, 17 Oct 2001 Mel Martin <firstname.lastname@example.org> writes:
> >Higher is NOT always better....N4KG
> If you only have one antenna at a fixed height it is!
> Sure, there are circumstances where a lower antenna will outperform
> a higher antenna, but a higher antenna gives better access to the
> longer paths, where signals tend to be weaker. For DXing, higher is
> always better (within reasonable antenna heights) for one antenna
> installations (the vast majority).
> It's still a good *rule of thumb* for most of us Tom! Obviously,
> serious contest stations are a very special case... pretty rare...
> except on this reflector, of course ;-)
Mel (no call given):
IF you put up a high tower, then I see NO reason that
you can't also side mount a second antenna to fill in the
pattern NULLS of the high antenna. These nulls can be
quite deep (10 to 30 dB) over several degrees of vertical
waveangles. Even a simple trap dipole on a tower leg
will be better than the high beam if the arrival angle falls
in the null of the high beam.
My TH6 at 80 ft is almost NEVER better than lower antennas
on 10M such as my TH7 at 40 ft or 5L10 at 60 ft (a real KILLER).
On 15M, the 80 ft TH6 is sometimes a good band opener / closer
but my 4L15 at 55 ft is consistently better for the EU run once
the sun has been up an hour. At N4AR's super contest station,
we consistently found that a little CC 4L15 at 50 ft would trounce
a 6L15 at 90 ft during the day.
I have told my Africa story countless times and whenever I compare,
my 40 ft high TH7 is ALWAYS stronger than my 75 and 80 ft antennas.
During the day the TH7 is often the best 20M antenna, at least from
Alabama to EU / AF. Others in TN and ALA with high and low antennas
see the same result.
With a 40 to 50 ft tower, I would go with a single tribander or 5 bander.
With a 60 to 80 ft tower, I would go with two antennas,
one at 40 ft, the other on top. The bottom antenna could
be a simple trap dipole or 2L tribander with a bigger antenna
on top. The top antenna WILL have nulls in the ranges
supported by the ionosphere on 10 through 20M.
My friend NN4T has built an elegant cost effective
contest station with 5 Rohn 25 towers. Antennas include:
TH7 on 40 ft tower with rotor
PRO57 on 120 ft tower with rotor
2L40 at 90 ft fixed on EU on same tower
204BA's at 90 and 40 ft on 90 ft tower, bottom fixed on EU
plus 2L40 at 100 ft on long mast
155BA's at 35 and 70 ft on 70 ft tower, bottom fixed on EU
105BA's at 30 and 60 ft on 60 ft tower, bottom fixed on EU
80M 4 square using 42 ft verticals
160M vertical (90 ft R25 top loaded)
These heights play extremely well.
To achieve any significant improvement he would
need to go to 120 ft R45 or R55 towers with 3 or 4 high stacks
and even then, during the day, I would not be surprised if the
lower pair weren't better to EU than the full stack.
You can never have too many antennas :-)
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