View Single Post
  #30   Report Post  
Old October 14th 14, 07:09 PM posted to rec.radio.amateur.antenna
[email protected] jimp@specsol.spam.sux.com is offline
external usenet poster
 
First recorded activity by RadioBanter: Jun 2006
Posts: 1,898
Default Short antenna = reduced power

rickman wrote:
On 10/14/2014 12:58 PM, wrote:
rickman wrote:
On 10/14/2014 1:21 AM,
wrote:
rickman wrote:
On 10/13/2014 11:45 PM,
wrote:


snip

9.87 nothing; the expression is unitless, i.e. a pure number without
units.

In the expression you have a length divided by a length, which cancels
into a unitles number.

As my old physics professor used to say, always check the units of your
answer; the arithmatic may be correct but it is meaningless unless the
units are correct.

Sample problem:

You drove 100 miles and used 5 gallons of gas. What was your mileage?

5 gallons * 100 miles = 500 gallon-miles --- wrong units.

5 gallons / 100 miles = .05 gal/mile --- wrong units.

100 miles / 5 gallons = 20 miles/gal --- correct units and correct answer.

I have no idea what you are going on about. Ok, 9.87 is a unitless
number. So is 33.043. Now what?


Exactly.

Since it is a unitless number, it can not be power as claimed.

Nor can it be a rule of thumb for power versus antenna length as a full
wave antenna does not radiate 4 (39.48/9.87) more power than a 1/2
wave antenna.

It is just nonsense.


Did you read the OP? He says:

"Has in the equation for radiated power the term"

He is just giving us a portion of the equation to show the dependence on
wavelength vs antenna length. But without the full equation we can't
know if there are mitigating factors.


And it is utter nonsense.

There is NOTHING about a 1 wavelength antenna that is 4 times that of
a 1/2 wave antenna, or 16 times than of a 1/4 wave antenna, which is
what the expression evaluates to.

The part L/LAMBDA is the fractional size of the antenna, and the rest
just numbers and I assume you have a calculator of some kind.

It has already been shown by others that, neglecting loss, all power is
radiated by an antenna no matter what the size.


--
Jim Pennino