After a week of being temporarily tied to trees and bushes, I finally got around to anchoring the antenna a little more securely using some eye screws. In the process I was able to raise the center of the antenna up another couple of meters which might help things.
One arm of the antenna is weighted down with a 2lb weight and floats up and down so that it can move with the trees. The center and other leg are tied down with enough slack to handle windy days. I may change them so that they’re just weighted down as well rather than tied off.
The coax got routed through the crawl space so I won’t have to worry about running over it with the lawn mower. It runs up the side of the house through another eye screw to the antenna feed line. When the radios get moved into their permanent location in the office/shack, I’ll look at some floor or wall connections for the coax.
I thought I’d see what I got out of EZNEC for modeling the three antennas on the wifi router. I treated each of them as single wires at 2.452 GHz about 1m off the ground (not the floor). Each wire was 8 cm long (0.654 lambda) spaced 8 cm apart. Radiation pattern is directed perpendicularly to the plane containing the antennas, so I have two of them pointed down (the wifi router is mounted to the side of the desk) and one pointed off to the side (there’s a power strip that gets in the way of it pointing down like the others).
After reading through some of the original documentation for NEC learning about the somewhat arcane input format (like MCNP, it can be pretty confusing at first), I’m liking how EZNEC simplifies and hides some of the complexity, but is still accessible if needed. When I start getting into building antennas, I might have to get a copy of it.
I was able to find some EZNEC model files for a G5RV antenna including the feed line and tried to modify it to match my current antenna setup. 40m and 80m are pretty much the same, but the radiation patterns for 20m and 10m become a little more complex compared to my initial model.
Using a tape measure and some very rough estimating, I came up with this plot of how the antenna is set up, without the ladder line in the middle (haven’t figured out how to add the feed line yet).
The far field plots EZNEC gives me look like this
The antenna model is pretty simple and nowhere near perfect. I’m probably missing a lot by not having the feed line included. Based on these rough simulations though, it looks like I’m warming a lot of clouds (ham speak for when your antenna is sending radiation mostly straight up).
Thanks to help from Dave/KF4FFO and Tom/AJ4UQ, the antenna is now hoisted up into the trees and plugged into the radio. I didn’t get a chance to grab my camera, but Tom had his to take pictures with.
My Hyperdog ball launcher and 4 fishing weights with some lightweight line that Dave brought proved to be a very effective combination for getting rope and antenna up into the tree.
The arms of the antenna are arranged in kind of a tilted/rotated inverted L, with one side angled down and secured to shrubs at one corner of the house, and the other side nearly horizontal. Perhaps not an ideal configuration for this. Right now everything is secured with temporary knots. I’ll spend some more time making some adjustments to the antenna before securing everything down properly.
SWR tested with Dave’s Youkits analyzer showed pretty decent SWR and impedance at 20m and 40m (~1.7 or so), so-so at 80m, maybe usable at 15m and 30m with some tweaking and not so good at 10m. Since the antenna should be able to do 10m, there’s probably some adjustment that needs to be done with how things are arranged. I think I’m going to have to get myself one of those Youkits analyzers. They’re pretty slick.
Radio receives pretty well on 20m and 40m so far. I can hear the WWV time signal at 5 MHz and 10 MHz pretty clearly. Heard lots of CW and digital signals on 20m after connecting up the antenna. Need to test how well I can get out next.
Right now the coax feed line just runs along the ground, but I think I’ll look into routing it through the crawl space so that it’s not lying out in the elements and won’t get run over by the lawn mower.
Now an interesting exercise will be to figure out how to use something like EZNEC and try to model what the antenna is doing.