[TenTec] Wet ladderline

[Steve Hunt]

On an unmatched line, losses vary with length because there are current 
peaks and troughs along the line. And because at HF losses are almost 
entirely copper losses, where the current peaks the losses will be high 
and where it dips the losses will be low.

Here's an example:

* Terminate 35ft of Wireman 551 in a 50 Ohm load. The total loss at 
3.8MHz will be 0.5dB
* Now double the line length to 70ft; the loss will be 0.58dB, not the 
1.0dB you might expect.

The reason is that the initial 35ft contains a current maximum (at the 
load) and consequently has relatively high losses, whereas the next 35ft 
contains a current minimum with relatively low losses. In fact that 
second 35ft of line with its 8:1 SWR contributes less loss than if the 
line was perfectly matched!

73,
Steve G3TXQ




On 09/08/2013 22:26, Stuart Rohre wrote:
> The comment someone posted about the losses varying depending on SWR 
> might be why results are not linear with length.
>
> Stuart
> K5KVH
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