RadioBanter - View Single Post

September 30th 03, 05:28 PM

On 30 Sep 2003 00:35:11 -0700, (Mark Keith) wrote:

The page of data called FCC figure 8 reveals that at 10Miles (actually
9.43 Miles) that the eh, tower, and top-hat are -4.24dB from the
reference and -15dB from FCC standard curve. The chart marked Exhibit
#1B (page 8) shows that further out at 20 Miles that the eh, tower,
and top-hat are -26.6dB from the FCC standard curve.

No bueno.

Perhaps I read the data out of order, or the charts upside down.

Yea, that PDF file kind of gave me a headache also...

Hi All,

On further review of the data offered, their tabular offering, the FCC
Ground Survey Map (M3_map.zip available at the FCC homepage), it is
evident I overstated the loss of the eh/tower/top-loaded antenna.

As noted above, this combination shows 4dB loss over their reference
comparison standing nearby their test (except in the direction of that
convenient passive radiator of course or with the concurrent
re-radiative properties of the nearby power lines the engineer notes
may affect readings). Employing the jpg file named 35e within the zip
file from the FCC, it is evident that the ground conductivity is NOT
2mS as computed, but 4mS as reported by the FCC. The location of
Eatonton is in the dead center of that quality of ground (not great,
but not as poor as 2mS).

I shrugged at what appeared to be perhaps an insubstantial difference
and reached for the calculator to see what the correlations would
bring if this data were applied to the FCC data of 4mS ground instead.
The loss is still apparent at -2.7dB. This agrees with the tabular
data instead of the misapplication of 2mS to the charting of it.

Off hand, it would seem safe to say that the eh/tower/top-load is an
average of mid 30's percent efficient.

Now, lets see, would a commercial station choose to replace a guyed
tower, with a top loaded short guyed tower, plus cost of do-dad to
enjoy the benefit of 1/3rd coverage? Let me be generous and return to
the -2.7dB valuation instead, but to observe that we are facing a
square law issue with population served. Those folks in the outlying
regions cover vastly more square miles than those in the near region,
so we will consider a population halfway between and note that
squaring that radius reveals half the listenership suffers degraded
service through this antenna substitution.

Economics 101: "How to kill a business without really trying."

Hi Stefano,

the simple english version
of the text above:
eh antenna is not efficient -
you seem to read
the press release english
easier than data numbers.

73's
Richard Clark, KB7QHC