Hi Dick, An EZNEC and SimSmith model of the on ground 1/4 wave vertical: https://www.kn5l.net/images/SS-KA5KKT-vertical.png
SimSmith R1 represents ground loss, the value set to establish a 50 ohm load at the transmitter, G in SimSmith. According to the models, the 7 to 7.3 MHz SWR is a little below 1.3. A flat measurement using the K3 SWR meter seams reasonable. My suggestion is to use a VNA to measure the antenna and system. John KN5L On 12/2/18 12:16 AM, Dick Dickinson wrote: > Thanks for the explanation, John. > > I’m not an electronically educated fellow, merely just seeking the > practical. > > A resolution to my post was provided in the suggestion that the apparent > 1.1:1 SWR might be the result of common mode current. Sure enough when I > installed a 1:1 current balun at the feed point of the antennas (2 > perpendicular Inverted Vees with a switchable common feed point), the value > went from 1.1:1 to 1.0:1 and the bottom of the SWR curves which also > broadened out. > > Still that doesn’t explain why the K3 was showing 1.1:1 while passing 1.0:1 > information to K3EZ, or so it seems. I don’t think that the K3EZ is > ‘measuring SWR’ rather merely posting information it is getting from the > K3…no different measuring device or location. Perhaps it is a sort of > ‘rounding error.’ By the way, for those who haven’t come across it, K3EZ > has the great feature of being able to step the K3 across a frequency range, > momentarily key it, step again, etc. and plot in text an SWR chart…a handy > feature for working with an antenna installation. > > Following is a situation that perhaps you have the theoretical background to > explain… > > I have a full-size monoband vertical for 40 meters. Simple architectural > aluminum tapering from 1 ¼” (?) in 6’ telescoping sections. The radial > field is designed to provide a 50 ohm match at the feed point…12 – 13’+ > radials. It is fed directly…no matching device with RG-213 from the remote > antenna switch about 50’ away at my tower. The coax from the rig to the > remote antenna switch is estimated to be ~ 50’ in length. A lot of the time > running K3EZ to sweep the band (typically 20 watts), it will indicate a > 1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps. Occasional deviation > from one K3EZ run to another might be due to variations in moisture content > of the ground or less than perfect connection to the vertical…an uncommon > situation. The K3 shows the same readings. > > Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable? > > Dick – KA5KKT ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
