[TowerTalk] Price of a decibel

Wed, 26 Apr 2000 16:14:16 +0300

Quite many of the comments on this reflector consider if a given antenna
setup is worth the trouble and the money or not. In order to analyze this
rigorously we need some numbers. 

Let me begin by defining a few standard setups that show a remarkable
difference in performance, say at the average around 10 dB each step in
practical DX type of operating. Right, I'm not saying that the gains of the
antennas differ much, they are really on the order of only a few dB between
each setup step. The differences come mainly from the antenna heights and
the related takeoff angle improvements. Remember, we are talking about DX
only. You may argue that the differences as seen in practical DX operating
are something else than 10 dB for each step (I have some doubts about the
biggest setup, never tried one.) Ok, let's then just see how you see the
differences and change the formulas accordingly. This is only the starting
point for the analysis.

And the standard setups are:

A - small system - a 40 feet tower and an ordinary trap tribander (e.g.
TH3).

B - medium system - a 85 feet tower and two bigger trap yagis including the
WARC bands

C - big system - a 120 feet tower with 6 el monoband yagis for the high
bands (including the WARCs) and a 3 el monoband yagi for 40. Phased wire
vertical arrays for 80 and 160.

D - a very big system - minimum 3 towers of at least 1 being minimum 140
feet high. Stacked monoband yagis for all bands 40 - 10 m. Ability to send
to at least two directions simultaneously on 10/15/20/40. Phased vertical
arrays for 80 and 160.

Then the prices. Suppose that the property to put up the systems is already
there and is not taken into account in the calculations. Let us only
consider the towers, basements, guy wires, rotators, cables, antennas, and
building permissions (if required). Let us also allowe one to buy something
new and somethind second hand. The price variations are of course quite
remarkable, but let's anyway try to get some kind of a budgetary price. 

I'd say that if you budget the following amounts in Finland you will quite
probably get the system mentioned: A = $1000, B = $4000, C = $8000, D = ?no
idea. Your QTH could have much different prices.

And now to the first conclusion. Take the A setup as the baseline. The first
10 dB enhancement in practical average DX operating costs $4000-$1000 =
$3000, which is $300 per 1 dB. The price of the next dB is then $400. As the
average one would conclude that the price of 1 dB is $350 when considering
antenna systems between setups A to C. 

Opinions, more accurate calculations? 

-Jari, OH3BU

--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm