Testing a Variety of Antenna Stuff

Great antenna weather here in South Texas. Clear skies and 74° F. A bit breezy which is always a bit of problem but provides some good portable antenna stress tests. I wanted to test the new modular mast supports so I decides to try an EFHW 20m half square supported by the two fishing poles. The poles are a bit short to support a 1/4 wave on 20m so I added a 2 foot PVC pipe extension to the mast support.

I was able to pound in the bases easily with a small sledge hammer. This was followed by a 2 foot 1-1/4″ pipe and a second 2 foot 3/4″ pipe with a 1/2″ pipe adapter on the end. I slipped the fishing poles over an end of 1/2″ pipe but their is enough play to switch the poles over in the breeze. I replaced the pipe with the fishing pole adapters I had made previously for  the beam project. This helped considerably. here are some views:

I made a couple of domestic SSB contacts and then switched to WSPR as NO5V/1. Will need to rethink a few things on the mounts but that was what the testing is for.

WSPR without an Antenna

I took down the 20m inverted-V late yesterday afternoon as we had high winds forecast overnight. I left the rig reading WSPR spots while I lowered the antenna and collected the feedline.

I had been collecting spots for about 15 minutes after disconnecting the feed-line and was surprised to see multiple spots were still being reported!

Modular Mounts for Telescoping Poles

I am working on building a set of modular mounts for a variety of telescoping poles for field use. I am using PVC pipe and fittings as well as some 3D printed parts. I have need to have a set of mounts that I can use in the field for the SOTABeams travel mast, Spiderpole and various 5-7m fishing poles. Here is what I have so far:

Ground “Stake”

Stake to PVC

Assembled to 1-1/4″ Coupler

3/8″ Threaded rod and nuts

The image on the lower left shows the mount configured to hold a fishing pole 2 feet off the ground. The image on the upper right is the configuration to allow ground mounting of the SOTAbeams travel mast. In both cases the mast slips around the mount. The threaded rod is 18″ long and is 3/8″ diameter. I have a version for the fishing pole that will raise it up about 8 feet using three additional 2ft sections of 3/4″ pipe. There is a guy ring for this version and should be of great use in the single radial vertical for 20m. Two of these will allow the 20m vertical beam.

I am ready to test this soon but we have been a bit to windy. I have two concerns with this design. The first is whether it can successfully support the larger Spiderpole. The second concern is pulling the mount out of the ground when done. I have some ideas for mitigating both that I will evaluate.

Having a pair of these handy will be great for testing a variety of configurations in the field.

Some Thoughts on the WSPR Challenge

The WSPR Challenge database is updated every day at about 3:30 UTC. This is 9 pm local time and well after the 20m band is closed at my QTH. An interesting effect of this is that the unique count that is recorded for my QTH over 24 hours tends to be a bit lower than the actual peak if I measure from say 23:00 UTC. The difference is not usually more than about 10 spots.

I also ran a probability plot of the top 100 unique spots for 20m over a three day period. On a normal probability plot a straight line would indicate a normal probability distribution of received spots. Here are the plots:

C1 & C2 were both the EFHW in vertical configuration. C3 represents the data from the last 20m inverted-V WSPR challenge. The mean is 145.8 vs. my score of 160 unique spots. There is daily ebb and flow in the Mean as I suspect the number of stations and propagation conditions all come into play.

There is a consistency here in that there are three distinct distributions visible. The lower, nearly vertical section represents the lower portion of the WSPR Challenge unique spots where the majority of spots reside. The portion angled at nearly 45° is the region where fairly good performing  antennas will be found. The highest scores are largely outliers to the rest of the  distribution.

These plots show an amazing consistency.

I have slowly worked my way up this curve on 20m. Early on I could make the WSPR challenge list but would be consistently on the lower distribution. Things improved considerably when I added a 1:1 choke. Noise floor dropped and I started receiving more spots. Are there other factors? Yes, there likely are and what drives the top is really interesting to find out.

One other WSPR performance factor is the ratio of hearing to heard spots when transmitting 1W. Anything above 85% indicates good performance. The Inverted-V showed almost 96% yesterday.

One other

RF chokes and WSPR

I setup the 20m inverted-V antenna with feedpoint at about 1/2 wavelength high. I made a few contacts then put it on WSPR as I wanted to compare to the vertical EFHW. This was all done in the early afternoon so the band was wide open. After several WSPR cycles I noticed I was averaging only about 5 or 6 spots on each cycle. This seemed odd as the EFHW was averaging 10 to 12 spots per cycle. I added a 1:1 choke at the end of the feed line running from the feed point to the ground. A second length of feedline runs from there to the shack. This choke was made with #14 house wire and has a bit of an impedance mismatch so the antenna tuner is needed.

The result? There was a marked improvement in the number of spots received and a noticeable lowering of the noise floor.

I would rather have tried the choke at the feed point but the weight on the mast would be a problem. Still, the improvement in receive performance by eliminating common mode current is significant. After 24 hours I am reading 169 receive spots vs 175 heard spots on 1W. Excellent antenna performance.

UPDATE 2/24/2020: WSPR  Challenge score came in at #29 with 160 unique spots and at #68 on the km Sum board. Very good performance overall.

20m EFHW Vertical Beam Results

After a full 24 hrs, WSPR results were somewhat mixed. The antenna performed very well per WSPR challenge results with 137 unique spots. This was good enough to score in the top third on the board. There was no clear indication that the antenna was more directional. The spot maps were almost identical to those done before.

Overall the antenna performs well. I’ll need to do some additional testing on the beam performance but this may have to wait as weather is changing. The South Texas wind machine is cranking up.

20m EFHW Vertical Beam Lives!

Great antenna weather today.  75°F and calm winds ar the QTH today. I moved the 20m EFHW and lashed it against a fence post. The SWR was adjusted so that it was at a minimum at mid-band. Lowest SWR was 1.08:1.

I cut a 33.9 foot director wire and mounted it on a second Spiderpole about 12 feet away from the driven element. The end of the wire of both elements was secured to the very top of the poles. The director is simply as wire hung along the pole.

As expected, the SWR increased somewhat across the band once the director was raised. This is a solid indicator that it is having an effect on the driven element. It is pointed roughly at a 45° bearing:

Made a few CQ calls with good result. I am seeing quite a few more signals on the waterfall. Now running 1W WSPR. I will update once I have some additional data.

Update: #53 on today’s WSPR challenge and with only 6 hours on the air! No spots to Asia. So I’ll get a full 24 hrs of data and then switch the two elements. I should see more spots in Oceania and Asia.