You have something terribly wrong. Two feet of coax at 7 MHz is negligible (~8 electrical degrees for solid dielectrics), even if its impedance is wildly different from 50 ohm.
Furthermore, any loss in the cable should reduce the SWR, not increase it. --- On Wed, 11/4/09, Don Wilhelm <[email protected]> wrote: From: Don Wilhelm <[email protected]> Subject: Re: [Elecraft] K3 SWR Accuracy - reprise To: [email protected] Cc: "Phil & Debbie Salas" <[email protected]> Date: Wednesday, November 4, 2009, 4:33 PM I can vouch for Eric's statement. I routinely calibrate KPA100 wattmeters for SWR using a precision 100 ohm dummy load (which should produce a 2.0 SWR). At 40 meters, I get 2.0 if I use a direct connection with a male to male adapter, with a 1 foot coax, it shows SWR=2.1 and with a 2 foot coax, it indicates SWR=2.2. The coax length is NOT negligible. BTW - my MFJ-259B shows the same thing with those same cable lengths. The Smith Chart constant SWR circle is for ideal (theoretical) conditions, and the real world conditions of cable loss and RF in places the Smith Chart does not consider must be factored in to explain phenomenon like this. Since most instrumentation is balanced/calibrated for 50 ohms, things agree when the impedance is 50 ohms resistive, but away from that point, other factors come into play. 73, Don W3FPR ______________________________________________________________ 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
