Here is an experiment to show what I mean. Take a transmitter and connect it to a 50 ohm dummy load through an antenna tuner. Put a wattmeter between the transmitter and the tuner. Now adjust the transmitter for 100 watts output and the tuner for 1:1 SWR. The meter reads 100W forward and zero reflected power. Now adjust the tuner for an SWR of about 2.5:1. The wattmeter will show forward power of about 120 watts and reflected power of about 20 watts. Did I increase the real power output of my transmitter? Did I make my signal stronger? No. I want a wattmeter that has an option to indicate 100 watts in this situation.
Vic K2VCO /4X6GP > On Jan 13, 2015, at 6:56 AM, Walter Underwood <[email protected]> wrote: > > No. That is wrong. Forward and reflected are aspects of the standing wave, > not power delivered. —wunder, K6WRU > >> On Jan 12, 2015, at 8:53 PM, Vic Rosenthal <[email protected]> wrote: >> >> What I want is just forward - reflected. Neglecting losses, this is what the >> tx is 'delivering'. In real life somewhat less gets to the antenna. >> >> Vic K2VCO /4X6GP >> >>> On Jan 13, 2015, at 3:19 AM, Fred Jensen <[email protected]> wrote: >>> >>> Well ... sort of. Some of the reflected power heats up the ATU and/or PA >>> depending on the match it sees [actually, some of the forward power does >>> too, tuners have forward losses]. "Delivered Power" is somewhat difficult >>> to calculate. Working into a matched, non-reactive load [common for AM >>> broadcast, at least a number of years ago], it's "I squared R" where R is >>> the radiation resistance of the antenna ... and some minor conductor losses >>> in the antenna. Things get pretty sticky if it's not a matched load. >>> >>> 73, >>> >>> Fred K6DGW >>> - Northern California Contest Club >>> - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015 >>> - www.cqp.org >>> >>>> On 1/12/2015 4:46 PM, Phil & Debbie Salas wrote: >>>> >>>> Actually, "delivered power" is pretty much what you are measuring. >>>> Remember that reflected power is re-reflected by the source and adds >>>> back into the forward power. So in your example, you are transmitting >>>> 1200 watts, having 200 watts reflected, then the 200 watts is >>>> re-reflected by the source giving you the 1200 watts. Of course, there >>>> will be transmission line SWR-related losses. >>> >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[email protected] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to [email protected] >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
