Tag Archives: 20m vertical beam

North American QSO Party – SSB

Saturday morning was a bit hectic for me this week as I had some errands to run early. I finished up by 17:30 UTC and started to setup for the North American QSO party. I decided to deploy the 2 element 20m vertical beam. I had taken it down due to inclement weather so this was a good test on how long it takes to setup in the field. All told it took about 30 minutes and that was doing things slowly. I have it pointed on a roughly North bearing.

I started operating the North American QSO party just after 1800 UTC and operated off and on through about 0000 UTC. I started on 20m and there was a lot of activity on this band. The 15m band was open but with much lower activity. 40m started coming alive at around 2200 UTC. Working search and pounce at a rate of about 25 Q’s per hour. All in all I ended up with 120 QSO’s to 106 unique call signs. I managed to work 40 US states, Barbados and several VE stations.Top state was California at 18.3% followed by 9.2% in Washington and 7.5% in Florida. Overall a decent effort with casual contesting.

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20m Vertical Beam Now Pointing to Japan

I moved the driven element of the 20m vertical beam to a bearing of about 330 degrees today. it took only about five minutes to drive in the pvc mounting pipe And rearrange the ground radials. The driven element is now further away from the A/C noise so that is now tolerable.

Early morning in Japan, signals started coming in and this time the difference between the vertical and the beam are significant. The S-meter indicated about a 2 unit difference. I did not close a QSO on phone but made a JT-65 to Japan.

Tomorrow I will collect some WSPR data and share a comparison method I am trying out.

 

My Never Ending Battle with Noise

I had to replace my central air conditioning about a month ago. It is a high efficiency type. The 20m vertical beam I have been experimenting with has the driven element about 25 feet from the outside compressor unit with the air handler about the same distance away just inside the house.

Whenever the fan is on (currently in heater mode) I get these noise spikes evenly spaced every 18khz across the 20m band that is being picked up by the beam. The vertical which is much further away does not pick this noise up on 20m but does see it on 18m. The Timewave does not cancel it out as the sense antenna does not hear the noise in its position inside the shack.

I’ll be moving the driven element of the beam to point towards Asia tomorrow which should improve things as it is further away from the A/C. Turns out that high efficiency A/C units these days tend to use PWM circuits for the fan control to optimize efficiency. This plays hob with RF above 20m.

Sigh…

More Tests of the 20m Vertical Beam Antenna

EZNEC modeling suggested a better response if I moved the elements of the 20m 2 element vertical beam closer together. The separation distance is now 11 feet versus the previous 18ft. Hard to tell if this worked on the basis of QSO’s completed. I will likely move the driven element so the array points to an azimuth of 330° as Japan seems to be opening up in the late afternoon.

Musings on Vertical Beam Antennas

I have been doing some EZNEC & Propagation studies on various vertical configurations. First off is the Ground Beam QEC antenna. The EZNEC model looks like this:

gbqec

The model indicates (and the performance seems to confirm) that this antenna is directive but the small number of ground radials causes gain to suffer. The main benefit of this antenna over a vertical is that it has some F/B reduction. Running some optimization on this models indicates some improvement by significantly lengthening the reflector. The gain increases slightly but the F/B ratio improves. Unfortunately, the reflector would have to be 7m long for a 20M antenna making deployment difficult using the telescopic fishing poles.

I was thinking about the homebrew Buddistick I built a while back and remembered it exhibited modest forward gain in the direction of the single elevated radial. Here is the model:

buddistick

This antenna is somewhat directional but also has considerable high angle radiation. It would still appear to be a better performer as a beam than either the 1/4 wave vertical or the ground beam QEC antenna. Drawbacks?…not as lightweight.

My final candidate is a 2 element vertical beam. Making a few compromises in mounting I can use the fishing poles to make a full size 1/4 wave vertical on 20m using a single elevated radial. The feed point is only 3 feet off the ground. Here is the model:

2el vert

This can be built in a manner very similar to the ground beam QEC. I just need to figure out how to mount the ends a bit higher. Horizontal space needed is about 16 feet greater than the ground beam QEC. here are the radiation patterns from the model:

pattern

To summarize this chart, the GB-QEC is almost equal to the 1/4 wave vertical in forward direction but with some rear rejection. The 20m Buddistick has greater forward gain, some rear rejection but considerable high angle radiation. This antenna makes a great Field day antenna at my QTH as it can point north and cover most of the USA and Canada. Finally the two element vertical beam provides 3db greater gain then the 1/4 wave vertical with 8db F/B ratio and good low angle radiation.

This info leads me to want to try the 2 element beam next. These parasitic beams are of course fixed in direction. The phased 2 element vertical array has the advantage it will provide some steering.

More Experiments with the 2 Element Vertical Beam Antenna

I previously reported on m y attempt top build a 2 element vertical parasitic beam antenna based on a design by JP1QEC. My first attempt had mixed results and I beileve the lengths I used were incorrect and tuning was negatively influenced by proximity to a metal hurricane fence.

I contacted Mot-San, JP1QEC and he provided my with additional information including a recent article that was published in QRP Quarterly. Here is the configuration based on Mot-San’s design:

20171127_172846054_iOS

I followed this design and supported the vertical elements with the fiberglass fishing poles. It is pointed to radiate at a bearing of 45° (NE) from my QTH. First tests showed the minimum SWR was around 13.2 Mhz. I shortened the counterpoise wires by about 4 feet and that brought the min SWR to the middle of the band:

20M BEAM Custom

So the first question is whether it is directional. It is. Here is a plot of FT-8 spots after a few minutes of calling CQ:

2017-11-27_8-36-27

Hard to tell if I have reasonable forward gain improvement. So far very little activity to Europe has resulted. Best conditions to the EU would be at 7am local time so I’ll try tomorrow. Meanwhile, I have received excellent reports on SSB domestically. A quick A vs B with the 1/4 wave vertical showed about 1S unit improvement with a conact I made in Colorado. This would imply some gain.

So far so good. I’ll play with this some more over the next few days. This does look like a potentially good antenna to use on Field day as it provides good reports and is easy to setup in the field.

More on the 20m Vertical Beam

The vertical beam is definitely directional. Unfortunately, I have no way to measure the gain. What I have noticed is that when I run this antenna on JT-65 I see much stronger reports from the direction the beam is pointed to versus the backside. Same goes with WSPR results. The antenna is also receiving well based on yesterdays WSPR challenge results as well.

I did some A/B switching between the beam and the 20m vertical while running JT-65. The beam sees signals coming in from Europe (very weak just above the noise floor). These disappear entirely when switching in the vertical. This could make a very nice antenna for next field day as it is easy to setup and from my QTH would cover much of the US my pointing due north.

Here is a picture of the antenna deployed in my backyard:

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These pictures show how everything is connected:

20170925_211621870_iOS20170925_211613096_iOS

At the feedpoint I have the homebrew 1:1 current balun. Each vertical element has two 18 foot radials laying on the ground. The two radial sets are connected by an 18.7″ ft wire. Pretty simple really.

A 20m Vertical Beam

JP1QEC developed a portable 20m vertical beam he calls the “Garden Beam Antenna“. I built one this afternoon and have it pointed towards Europe. Construction is stratightfoward. I used a fishing pole to first make a 20m 1/4 wave vertical. It has two ground radials that are about 18 feet long. A third radial extends 18.7 feet from the driven element in the direction opposite where you want the main energy to go. This is connected to two more 18 ft radials and the vertical reflector element also mounted on a fishing pole. I ended up with a very flat SWR of 1.6 across the entire 20m band. I suspect that there needs to be some tweaking to optimize the pattern but I am seeing some directionality based on signal reports from making some JT-65 contacts. The beam is pointed on a bearing of about 40°. I get strong reports from stations in the northeast while stations on the west coast are copying my signals considerably weaker. I made several SSB contacts with most reporting 59+. I’ll be testing the configuration in some more depth over the next few days and comparing with EZNEC results.