TLD software appears to satisfy that test. What's interesting under your
test set of parameters is that power delivered to the load peaks when the
complex Z at the load is opposite in reactance at the Tx end, but the
resulting Z values are equal. For example, if you use a load of 150 +j130,
the resulting complex Z seen at the Tx is 150-j130, resulting in 99.7% of
power reaching the load. The two resulting impedances are exactly equal
being just under 200 ohms. I am using 10 ft. of RG-213 (vf = 0.66) for the
simulation.
By contrast, under a matched condition, where the termination is 50+j0,
power delivered to the load is only 99.17%. Small differences for sure, but
the result is very interesting and counterintuitive. According to TLD, the
higher power delivered to the load under the mismatch condition is the
result of loss attributed solely by SWR actually going negative in value
(-0.024 dB).
Paul, W9AC
----- Original Message -----
From: "Steve Hunt" <steve@karinya.net>
To: <towertalk@contesting.com>
Sent: Tuesday, November 30, 2010 7:29 AM
Subject: Re: [TowerTalk] tuners and power rating
> The most comprehensive calculator I know is Owen's at:
> http://vk1od.net/calc/tl/tllc.php
>
> A good test for a calculator is to look at the loss it predicts for 10ft
> of 50 Ohm coax at 3.5MHz with a 150+j0 load (VSWR=3:1); the loss should
> be about **half** the matched loss.
>
> Charts which imply - without any caveats - that a particular value of
> VSWR always adds a fixed "excess loss", are misleading and show a lack
> of understanding of the loss mechanisms.
>
> 73,
> Steve G3TXQ
>
> On 30/11/2010 00:04, Rik van Riel wrote:
>>
>> After some searching around the web, I found an online
>> transmission line calculator that does take these things
>> into account:
>>
>> http://www.stroobandt.com/antennas/tl-calculator.html
>>
>> It does indeed give interesting and different answers
>> than the coax calculator I used before...
>>
> _______________________________________________
>
>
>
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