Tag Archives: 20m vertical beam

Update on the 2el Vertical Beam

I guyed the antenna elements after finding it survived the night. here is a view of the antenna:

IMG_1505

I know it’s hard to view but the elements are there. 😉

This antenna is working very well and has scored the past couple of days into the top 25 in the 20m WSPR challenge.

 

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Field Day and the 2el Vertical Beam

I came across an interesting read from Jim, N2GXJ entitled “Thinking about Field day Antennas“. This talks about Field Day scoring and how to improve your score. He points out that the key to Field Day comes down to the sheer number of QSO’s you make irregardless of where they are from. Jim starts by looking at poulation density from the US Census as an indicator of where ops will be located:

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This map tends to confirm my previous experience that the bulk of contacts are made up and down the east coast and in California. Last year I ended up running at 45W due to poor propagation and did notice many stations coming in from California. I made the mistake of not working more of them.

So from my QTH in South Texas I need to target the East and West coasts with daytime activity on 20m and 15m. The 2el vertical beam for 20m will definitely be a good choice for pointing to the east coast and should let me go back to QRP levels. I’ll try and test this out this coming Saturday if the weather holds (good to test the battery system while I am at it).

The 2el Vertical Beam Lives!

Made a run to Home Depot this morning and bought the PVC bits I needed to build the 2el vertical Beam I described in a previous post. The PVC is for the antenna mount to raise the feed point up to about 8 feet. I had some issues laying the elements out in the backyard as a tree was in the way. The two elements are 16 ft apart which is a bit further than the 13 feet modeling showed was optimum. I started by setting up the driven element. this went together very similar to the homebrew Buddistick with the exception that the fishing pole allows me to go full length. It tuned under 2:1 SWR across the whole 20m band. The reflector was even easier as it does not need to be tuned. I used one continuous piece of wire for the element and radial and keep the distance to the radial end at 14 feet. The beam is pointed in roughly a 45° bearing towards the northeast USA and Europe.

I should mentioned I did all this in a dead calm and in very muggy conditions outside today. I did not like the was the PVC was bending but rather than properly guy them I opted to try the antenna out a bit first…what could go wrong? I ran WSPR for about 2 hours with the following result:

2018-04-07

Note the high density of spots to the NE and the two spots to Europe. Pretty good for this time of day. Some SSB work towards the Mississippi QSO party yielded several “strong signal” QSO’s. I also made a QSO to Spain. After I closed that QSO, I switched to the S9V31 and noted a drop on the S meter from S4 to S1 when he was transmitting. Not sure what to make of that as 3 S units represents an 18dB change in signal strength. Perhaps the difference in pattern?

Did I mention what could go wrong? Let me first mention that PVC is like a wet noodle. The reflector was supported somewhat by some nearby tree branches but the driven element was not cooperating. I leaned a step ladder against it to provide a bit of support. Now remeber I did not guy it down as I was anxious to test it out. The weather shifted while I was gathering data. A cold front blew in and it started to rain lightly and the wind started gusting. The antenna has not failed but I don’t expect it to stay up through the night. The driven element is leaning over quite a bit in the breeze and I expect it to flop over at some point. The good news is this is hard to damage.

I’ll guy it up tomorrow for more extensive use. I think this is finally a winner in the gain department. Setup is fairly easy with the only thing I need to improe being how to get the feed point to 8 feet and still keep it portable.

Next Vertical Beam Experiments

My next experiment with a vertical beam antenna for 20m is coming up this weekend. My plan is to start with essentially a full length “Buddistick” on 20m using a fishing pole. I am going to plant 2 feet of a 5 foot 3/4″ PVC pipe as an initial support. On top of this will be another 5 foot 3/4″ PVC pipe joined with a pipe coupler. On top of this is a 3/4″ pipe coupler plus a 3/4″ to 1/2″ pipe adapter. A 12 inch length of 1/2″ PVC pipe will go on top of that and the telescopic fishing poles will slip on to this. Both the reflector and driven element will be mounted in this way. I may have to guy the mounts but short guys should work.

The driven element will have it’s feed point at 8 feet. The vertical element will be 16.5 feet long. The radial will be 17 feet long and slope down to an electric fence post at 4″ high. The reflector will be 13 feet away and be identical to the driven element except the vertical wire is 17 feet long followed by a 17 ft radial also mounted 4 feet high. Here is some EZNEC plots of this configuration:

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I am expecting that this configuration will be below 2:1 across the whole band, provide good low angle radiation, 3-4 dBi of forward gain and 10dB of Front to back. This should be easy to build and deploy

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.

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:

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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:

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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.