Topband: OWL loss. (was Re: K2AV 160m Folded Counterpoise Antenna - New Details Posted)

[Richard (Rick) Karlquist]

On 12/9/2011 8:05 AM, ZR wrote:

>
> Using a 120VAC 60Hz source and a 10A load the loss in 850' of #4 copper is
> 5.1V or 4.2%
>
> With aluminum it is 7.3V and 6.1%.
>
> It only gets worse at RF and once you reach about 3dB loss the input VSWR
> flattens out until it appears to equal the line impedance. Ground losses in
> a vertical have the same effect.
>
> Adding a pad between the signal source and DUT in the lab is the standard
> procedure to eliminate a matching problem.
>
> Carl
> KM1H

In the example above, the load impedance is only 12 ohms.  For my OWL,
the load impedance is 450 ohms.  The line is not connected directly to 
the vertical, which has more than 12 ohms of impedance anyway.
Terman's handbook (and some ARRL handbooks) show OWL loss and predict a 
few tenths of a dB, like I am measuring.  Add 28% increase in loss for 
aluminum vs copper.  (This is the square root of the ratio for DC; the 
difference is that the skin depth of aluminum is greater than copper, 
and reduces the loss adder for aluminum vs copper).

Rick N6RK