October 8, 2017
Posted by on
Rudy Severns, N6LF, published a paper entitled “Measurement of Soil Electrical Parameters at HF” where he shows several methods of measuring the electrical properties of soil. I built an OWL probe using his directions made from two parallel 1/2″ aluminum rods spaced 4″ apart and 11″ long.
Once assembled I measured the capacitance of the probe with the L/C capacitance meter which measured it to be 6.16 pF. I inserted the probe in the ground around my vertical antenna then connected the RigExpert AA-230 Zoom and measured impedance at several frequency points in the HF bands. The Resistance and Reactance are used to calculate the soil conductivity and Er values. Here is a graph of the results:
The data collected at this one point confirms that the soil in South Texas is quite good in terms of conductivity and Er. I will use these values when modeling antennas with EZNEC. This was the initial test and I will likely try some other areas of the backyard and see how much it varies and whether the data is consistent
June 13, 2017
Posted by on
I was going to try and adjust the loading coils on the homebrew Buddipole but after reviewing the SWR plots in more detail I have decided against this. The resonance point is on the high end of the band but I’ll be operating mainly voice. The SWR is below 1.6 across the band and the reactance is within ±3 Ohms of the resonance point. Better to leave it alone at this point.
I did add a couple of cable ties to the arm to allow me to better control the antenna swinging in the wind. I am working to build another 1:1 current balun which I will replace the BNC to binding post adapter I am runing now. It will be interesting to see if adding this balun will change the SWR curve. Here are the current curves:
Hopefully I can retest the deployment of this antenna this weekend perhaps at 20 ft and with luck maybe at 30 feet on the military mast.
May 27, 2017
Posted by on
Sometime ago I built a homebrew version of a Buddipole horizontal dipole antenna. I only deployed it once to test and have not really used it much since. I am considering using this antenna for Field Day this year on the 20m band and wanted to test it out. Happy I did for several reasons. Here is the antenna deployed at 16ft with a painters pole:
The antenna is guyed at two levels. The painters pole is inserted into a speaker stand tripod. Here is the SWR plot:
Most of SWR is below 2 however the resonance point is outside the band on the high side. So I have to lengthen the antenna slightly. The whips are already at their max so I will have to adjust the loading coils. One more turn on each should give me room to adjust with the whip lengths if necessary.
Something else that needs to be addressed is that the antenna swings around in the wind. I need to add an attachment point for a separate line to secure it from swinging. The old “Armstrong” method of swinging the antenna around. Finally, I need to put a true 1:1 current balun at the feed-point. I have the kit to build one and will do so this week.
The antenna has performed well. I called CQ this afternoon and made 5 contacts from South Dakota to Florida and North Carolina. Band Conditions have been fairly bad with considerable QSB. Europe will open up in a couple of hours and will try it again then.
April 28, 2017
Posted by on
My posts on the Mini60 antenna analyzer remain the most popular views on this blog. I have not been using it much since I acquired a RigExpert AA-230 zoom. The RigExpert is so easy to use and provides a wealth of information when tuning antennas. That being said, I have not given up on the Mini60 as I intend to use it on Field Day.
I am going to be retro-fitting a bluetooth module to the Mini60 over the next few days. I need a USB to TTL adapter to program the bluetooth before installation and then wire it into the PCB. Worst case I end up trashing the mini60…best case I’ll have a wireless Android interface for this over bluetooth. Stay tuned as I’ll post some detail on how this proceeds.
December 28, 2016
Posted by on
One page that folks following my blog seem to gravitate to is my review of the Mini60 antenna analyzer.It is the Sark 100 copy sold on Ebay and produced in China. I personally have found this analyzer to work quite well and I have used it exclusively to test out my antennas. Your mileage may vary.
Now that I am doing some additional antenna work I have purchased a RigExpert AA-230 Zoom. This unit is a bit pricey compared to MFJ units and certainly to the Mini60 but from what I have done with it thus far it is well worth it. I’ll publish a comprehensive review later but for now I am sold on it. It is light, provides accurate and quick scans, has an impressive array of features including cable TDR testing and a great USB interface. The software works great with a PC and can save files in a format that Zplots can read.I used it for the first time in the field on the 40m loop and it made short work of tuning it. The interface takes a little getting used to but overall is very smooth to handle.
I will not be getting rid of the Mini60 as for quick and dirty measurements it still can’t be beat for the money. The RigExpert will be for more advanced testing and data collection and will of course help me with 2m antenna work.