If you look at the technical data for a Belden solid dielectric RG58
(say 8259) and compare it with a foam dielectric RG58 (say 7807) you'll
see that the centre conductors are significantly different diameter:
0.035" vs 0.044" - they have to be to achieve the same 50 Ohm
characteristic impedance with different dielectric materials.
The difference in loss is almost totally down to the smaller conductor
diameter, not to differences in dielectric loss.
73,
Steve G3TXQ
On 26/01/2012 13:43, Carl Moreschi wrote:
> Here is some data taken from the ARRL handbook on losses for various
> transmission lines at 14 mhz per 100 feet.
>
>
> RG-58 hard dielectric 1.8 DB
> RG-58 foam dielectric 1.5 DB These two have the same I squared R loss
>
> RG-8 hard dielectric 0.85 DB
> RG-8 foam dielectric 0.6 DB These two have the same I squared R loss
>
> Open wire line air dielectic TV type less then 0.1 DB
>
> As you can see from above, the dielectric has significant meaning to the
> loss.
>
> Carl Moreschi N4PY
> 121 Little Bell Dr.
> Hays, NC 28635
> www.n4py.com
>
>
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