RadioBanter - View Single Post

Registered User · December 13th 10, 01:34 PM posted to rec.radio.amateur.antenna

On Mon, 13 Dec 2010 00:13:10 -0000, wrote:

Registered User wrote:
On Sun, 12 Dec 2010 17:32:53 -0000, wrote:

Registered User wrote:

Efficiency is a measure so it must have one or more dimensions

Efficiency is a ratio usually expressed as a percentage and has no dimensions.

The efficiency of an antenna is the radiated power divided by the input
power.

There are two dimensions in the calculation, radiated power and input
power. Although the units of measure associated with the dimensional
data may cancel the dimensional metadata doesn't.

x power/ y power = x/y

The units cancel to form a dimensionles, unitless, ratio.

This is grade school math.

unitless yes and in the example given no metadata is provided. The
result of the calculation is just a meaningless number.

What of the equation :
x units of radiated power / y units of input power
The units cancel but the metadata doesn't. The result is a number that
describes the ratio of radiated power to input power.

The phrase "dimensional metadata" is meaningless babble.

You can call it meaningless babble but in its simplest form
dimensional metadata provides meaning and additional information to
raw data. You have used dimensional metadata in this thread and
unknowningly use it every day. The phrase "80% antenna efficiency"
contains both a unitless number and dimensional metadata. In this case
the metadata describes the dimensional calculation used to produce the
result. Remove the dimensional metadata and the phrase becomes "80%".
The latter has no context and conveys no meaningful information
because it represents a ratio of two unknowns. It could be a ratio
representing antenna efficiency or the price of apples compared to the
price of oranges. Raw data without metadata is meaningless babble.