Jim, Rudy Severns, N6LF, is developing a new 24" soil probe. In the process he discovered that common-mode current on the long cable he runs to his desktop computer from his older VNA can seriously
I've been told I should post a link to this writeup I did several years ago: http://ham-radio.com/k6sti/pileup.htm As noted in the analysis limitations section, I'm not sure how much it really adds.
Here's how TA handled stacking: -- STACKED ANTENNAS -- TA can plot the pattern for a pair of antennas with vertical and/or horizontal offset. First snapshot the pattern with the antenna at one stacki
This writeup uses a trapped triband Yagi to show how to create wideband models for antennas with coils: http://ham-radio.com/k6sti/wbc.htm The method uses an updated version of my coil inductance and
K9YC: "The likely unknown here is the soil characteristic plugged into the model, as compared to what we have. :)" I'll use this as an excuse to plug my ground probe calculator. Build your own ground
Rob, K5UJ: "For US hams wanting to get a rough idea of where they land in the ground conductivity lottery, you can look at the high def. FCC map and either cheer or weep. But, keep in mind, the bound
Paul, W9AC: "Isn't the measured probe result only useful for near-field system efficiency analysis? By near-field I mean to obtain system efficiency within a wavelength or so of a vertical radiator.
The example shows how to automatically optimize an antenna with traps: http://ham-radio.com/k6sti/wbc.htm The trap resonance result deserves further study. Optimizing a 10/15m trapped dipole gave the
I tried optimizing a loaded dipole for 3.525 and 7.025 MHz. I used an RLC load to properly represent a self-resonant coil. After optimization, the load wound up out 40.5' on a 53.9' wire (one side of
I probably should have included this image of a full-length, resonant, 3/2-wavlength dipole: https://i.postimg.cc/2Sq0dJTd/full.gif Brian _______________________________________________ _____________
Since we're on the subject of loading coils, I wanted to pass along an interesting practical study of coil loss due to corrosion: https://www.w0qe.com/Technical_Topics/inductor_Q_tests.html I mention
A ground probe lets you measure your local ground permittivity and conductivity for antenna analysis. Accurate models of verticals and low horizontal wires need realistic values. The probe uses two m
Helpful article on the properties of various 3D-printing plastics: https://www.3dnatives.com/en/plastics-used-3d-printing110420174/ Check the dielectric constant and dissipation factor of the plastic
Can you cite some examples of plastics that have high loss at HF and low loss at UHF or vice versa? I've never encountered that phenomenon. Rick, see CUSTOMIZE.TXT in gnd.zip (download from the COIL
"My final choice was slotted acrylic bars for strength, water and UV resistance, and ease of solvent gluing the wires in place." Grant, after seeing several neat coil form designs in the style of Air
I've applied the Getsinger corrections for transmission line end effects to leads in my coil calculator (http://ham-radio.com/k6sti/coil.htm) and rods in my ground probe calculator (http://ham-radio.
Accurately calculating rod length and antenna reactance for a hairpin match turned out to be more complicated than I expected. I realized pretty quickly that my boom model was dubious. I abandoned it
"NEC does use a simplified model for the "wire" - it takes into account dielectrics and skin effect (I'm in the middle of figuring out what ZINT does, which is the core of the "resistance and inducta
Rudy Severns, N6LF, has updated his writeup on ground parameter measurement with several new probe designs. A ground probe and NanoVNA let you measure the permittivity and conductivity of your local
Rick, see Rudy's original writeup where he goes into this in great detail. His recent update is just an update on that earlier work. He doesn't repeat the basics. It only gives a spot measurement of