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## Re: [TowerTalk] tuners and power rating

 To: Re: [TowerTalk] tuners and power rating "Paul Christensen" Tue, 30 Nov 2010 13:43:16 -0500 mailto:towertalk@contesting.com>
 ```Thanks Steve. That makes perfect sense. What's a mystery is why the loss attributed to SWR under that condition shows as a negative value in TLD, albeit a small amount. The inverse of loss is...well, gain! Paul, W9AC ----- Original Message ----- From: "Steve Hunt" To: Sent: Tuesday, November 30, 2010 1:24 PM Subject: Re: [TowerTalk] tuners and power rating > Paul, > > It's not really counter-intuitive when you remember that at HF the vast > majority of feedline losses are I*I*R losses and therefore driven by the > current that is being carried. If we have a 150 Ohm Resistive component > to the load - no matter what its Reactance - the current into the load > must be 57.7% that of the matched case when dissipating the same power. > That means that *right adjacent to the load* the feedline power loss per > unit length will be 1/3 that of the matched case. It's only further back > along the line, where the current standing wave begins to "develop" > higher currents, that the losses increase and eventually overtake the > matched-line losses. > > ARRL's TLW software gets it right. Now, if they would just correct their > hopelessly optimistic loss figures for ladderline, it would be a useful > programme ;) > > 73, > Steve G3TXQ > > > > On 30/11/2010 14:09, Paul Christensen wrote: >> 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" >> To: >> 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... >>>> >>> _______________________________________________ >>> >>> >>> >>> _______________________________________________ >>> TowerTalk mailing list >>> TowerTalk@contesting.com >>> http://lists.contesting.com/mailman/listinfo/towertalk >> _______________________________________________ >> >> >> >> _______________________________________________ >> TowerTalk mailing list >> TowerTalk@contesting.com >> http://lists.contesting.com/mailman/listinfo/towertalk >> >> > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] tuners and power rating, (continued) Re: [TowerTalk] tuners and power rating, jimlux Re: [TowerTalk] tuners and power rating, Rik van Riel Re: [TowerTalk] tuners and power rating, jimlux Re: [TowerTalk] tuners and power rating, Rik van Riel Re: [TowerTalk] tuners and power rating, jimlux Re: [TowerTalk] tuners and power rating, Rik van Riel Re: [TowerTalk] tuners and power rating, Rik van Riel Re: [TowerTalk] tuners and power rating, Steve Hunt Re: [TowerTalk] tuners and power rating, Paul Christensen Re: [TowerTalk] tuners and power rating, Steve Hunt Re: [TowerTalk] tuners and power rating, Paul Christensen <= Re: [TowerTalk] tuners and power rating, Steve Hunt Re: [TowerTalk] tuners and power rating, jimlux Re: [TowerTalk] tuners and power rating, Paul Christensen Re: [TowerTalk] tuners and power rating, jimlux Re: [TowerTalk] tuners and power rating, Steve Hunt