[TowerTalk] 75ohm cable

[Roger (K8RI)]

On 7/20/2010 1:39 AM, Jim Brown wrote:
>> True, but the additional loss in the coax depends on the matched loss
>> and the additional loss (in the line) due to SWR.  With a low loss line,
>> it's miniscule, but if using RG8 on 440 it could be substantial.
>>      
> WRONG!  The additional loss due to mismatch does NOT depend on the
> matched loss. It depends ONLY on the mismatch at the load.
Then why do we refer to a set of tables to get the additional loss based 
on SWR AND the loss in the coax.
Coax with a higher loss will show higher additional loss with increased SWR.

73

Roger (K8RI)
> In fact, the
> higher the MATCHED loss, the less that mis-match matters. One of the
> things that the Smith Chart teaches us is that loss causes the SWR to
> converge toward 1:1 (and the impedance at the TX to be equal to Zo. The
> more matched loss, the faster it converges.
>
> 73, Jim K9YC
>
>
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