[Towertalk] 75 ohm hardline cable again

[n4kg@juno.com]

Graphs of cable loss vs frequency for MANY types of
cable, including RG58, RG59, RG8, RG213, CATV
hardline and 50 ohm hardline can be found in the
Transmission Line Chapter of any ARRL Antenna Book
(and probably in the ARRL Handbook as well).

0.750 inch diameter CATV Hardline 
has ~0.3+ dB loss at 30 MHz per 100 ft.

0.500 inch diameter CATV Hardline 
has ~0.5   dB loss at 30 MHz per 100 ft.

The line for 50 ohm hardline appears to be about 10%
to 20% lower than the line for same size 75 ohm hardline.
This contradicts the theory that for identical construction,
75 ohm line should have the lowest loss so apparently
there are some other differences in the construction or
some other reason for this discrepancy.

Loss drops by the square root of frequency, i.e., multiply the loss 
by 0.7 at 1/2 the frequency or multiply by 1/2 at 1/4 the frequency
(loss at 40M is 1/2 the loss at 10M).  This is generally true for
most cables.

Tom  N4KG

On Mon, 19 Aug 2002 00:14:08 +0000 epetek1@att.net writes:
> Following up on earlier thread- does anyone know what 
> the losses are in .750 TV hardline cable? How does it 
> compare to 50 ohn 1/2" hardline. Lookin' fer ur 
> responses - Pete W2YG
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