Tag Archives: 1/4 wave vertical

2018 ARRL DX SSB Contest

Worked the ARRL DX SSB contest this weekend and managed to get 100 contacts over the course of the past 48 hours. I did not operate to aggressively but did operate with spotting assistance. I worked 46 countries on 40m, 20m, 15m and 10m. 34% were in North America, 30% in South America, 16% in Europe, 7.5% in Asia and 10.8% in Oceania. No contacts in Africa this year. None of the worked countries were counted as new ones. All in all not bad and a lot of fun considering the band conditions were pretty bad (SSN=0 SFI=67). North America was dominated by 20m, South America with 15m, Europe on 40m, Asia split evenly on 40m and 20m and Oceania also split between 20 & 15m. All in all 20m was the more difficult band to work with many really weak signals heard here at the QTH. 40m comes alive in the early evening into Europe and Japan in the early morning. 15m had less overall activity but had many strong signals from central and South America. My score works out to 22,572 with 100 QSO’s. The DX stations responded with power of 1000W about 90% of the time with the lowest power as 100W. Good test of the vertical 1/4 wave antennas!

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40m 1/4 Wave Re-build

I took down and rebuilt the 40m 1/4 wave vertical this past Saturday. I am using the same mast and vertical radiator as before but I have added the radial plate with 20 ground radials. I replaced the coax pigtail with the small vertical junction box I had been using previously. Overall, glad I made these changes as the connections were getting rusty and there was clearly some water getting into the feedline. I will start working to pin the radials down so I don;t have to pick them up when m,owing the lawn. I also plan to put up the 20m vertical element as before so I can have a resonant antenna on 40m, 20m and 15m (3rd harmonic of the 40m). Once the 20m vertical is up I can use it for A vs. B comparisons with the 20m half square. Also looking at a shortened 80m vertical to add to this set of “fanned” verticals.

A Quick Radial Experiment

I added about 12 feet to two of the 40m quarter wave radials, trimmed the ends so there is bare copper and dropped then into the resaca in the backyard. For those not familiar with the word “resaca”, it is a type of oxbow lake which in my case was a channel of the Rio Grande River that was cut off from the river and forms no inlet or outlet. The water is fresh but somewhat brackish.

The result appears to be minor. SWR dropped to 1:1 but not sure if it is because of the longer wires or the contact with water.

40m FT-8 to Asia Working Again

I have been having good luck working DX into Asia on 40m FT-8 the past few mornings. The opening have lasted here well after sunrise until about 8:30am local time. I have made numerous contacts the past few mornings into Japan, Indonesia & the Philippines. The band had seemed to be shifting but it was likely just poor propagation conditions. Glad to be working these contacts again.

Inadvertently Stress Testing a Homebrew Buddistick

I took out my homebrew Buddistick over the weekend to test its performance versus the full size verticals I have been playing with. I haven’t really deployed this in some time so I was able to make some comparisons to some of the antennas I have been working with lately, namely the 1/4 wave ground mounted verticals. Setup up was about as easy as I remembered it but certainly more complicated than the ground mounted vertical. It is also heavier than I remembered it to be. I had it setup with three guy lines and a single elevated radial and it tuned to 1.46 SWR on the 20m band. On 20m it is not a full size radiator and relies on a small coil to bring it to resonance.

Performance was actually quite good on 20m WSPR. Two days in a row I made the WSPR challenge board. It still remains about 20 spots below the nearby station of N5CEY. The number of spots on 1/2W transmit was about equal to the number of receive spots which I am finding to be a good indicator of antenna efficiency. Thais tells me what I already knew, that is, it is a good QRP field antenna.

The antenna went up Saturday afternoon and stayed up through Monday afternoon. Monday it got breezy here at the QTH. Wind speeds picked up to around 20mph with gusts to 35mph. At some point, the camera tripod failed at the point where the PVC pipe meets the tripod. The whole mess came down hard. Fortunately, the whip was spared any damage and the tripod can be repaired.

IMG_1444

For my next trick I am going to try and replace the whip with a fishing pole and wire with an elevated radial. Should be much lighter. It has also proven to be much more resistant to the “valley Wind Machine” that builds up around here this time of year.

ARRL DXCC

I have spent the last few months painfully creeping towards 100 LoTW confirmed DX contacts in order to earn the DX Century Club Award. The 1/4 wave vertical antennas and digital contacts using JT-65 and now mainly FT-8 have gone a long way to get my entity count up. I managed the DX100 on QRZ.com last year but gaining the DXCC with only LoTW QSL’s has been much slower. Sometimes I get a new one but they don’t confirm on LoTW. Over the last month I had been holding at 99 entities. Yesterday I got a flood of confirmations from a Dxpedition to Galapagos Island that put me over the top! Looking forward to proudly displaying the DXCC award soon!

Junction Box for Vertical Antenna

Here is a simple junction box I built to simplify setting up a vertical antenna. The hardware is all stainless steel. There is a 1Meg resistor across the feed-point to bleed off any static. This box will replace a coax pigtail. Ground radials connect to one lug and the vertical element to the other. The coax from the ugly balun connects directly to the UHF connector.

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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.

ARRl Sweepstakes 2017 – Roundup

The 2017 ARRL Sweepstakes was this weekend. I had some personal issues to deal with on Saturday and did not actually start working the contest until Saturday evening, 5 hours after the start of the contest. At this time of day 20m and up were closed down at the QTH. I started by working on 40m and spent most of my time there. The 40m 1/4 wave vertical worked great.I made contacts easily and the exchange was copied 100% about 95% of the time. I tried 80m on both the vertical and the DXtreme end fed and while both tuned up initially, there were problems when it came time to actually make contacts. The auto-tuner would start trying to re-tune every time I went to transmit. I only made one contact on 80m to North Texas. I worked Saturday until about 11:30 pm.

I ran a few more contacts on 40m early on Sunday morning before I left for church service. I picked up again in the early afternoon and started working on 20m and 15m. 20m was very busy and there was considerable QRM. 15m was open but there were significantly fewer stations. I struggled to make contacts initially but after about an hours they started to come in easily. I suspect that this was due to propagation changes. I quit around 5:30pm after making a few final contacts on 40m.

All in all, I worked the contest for only 6 hours and 33 minutes, made 124 QSO’s across 63 of the 83 available sections. I worked enough “rare” states that I completed my ARRL WAS for the phone endorsement using only LoTW confirmations.

What worked:

  1. Very pleased with the 1/4 wave vertical, with the IC-7300 and received several complements on my audio quality.
  2.  The Timewave ANC-4 has become easier and easier to setup and use. It is very valuable when noise conditions changes during the day. I am finding it to be effective at reducing shack noise.
  3. N1MM logger+ is very very handy for contest especially with the spectrum display on the PC with the IC-7300

What I need to improve:

  1. I don’t have a capability to work 80m and below effectively. This is a problem that I need to address as there were rich contact opportunities on 80m during the evening hours. I thought I could use the DXtreme for this purpose as I did in 2015 but I suspect there is something with that antenna that has changed. It may be time to bring it down.
  2. My foot gets tired using the foot switch. I switched back to the hand switch occasionally but I need a better switch for this purpose.
  3. Need to work on adjusting the receiver when there are many stations close in causing QRM.

I don’t really compete in contests for the prizes or fame. I work contests to test my setup over various bands and look for areas that I can improve. I think I was successful in that this year. That being said I was only 20 sections from a clean sweep mug so who knows? maybe next year?

 

 

 

A 20m 2 element Vertical Array

I previously reported on my tests of the Garden-beam antenna. While I haven’t given up on this design I did come across some “gotchas” in my implementation. Working on this antenna lead me to think about my soil conditions which I have now measured and confirmed to be quite good due to our proximity to the Gulf coast. I also starting thinking about implementing a 2 element vertical array. So here are a few options that I am looking at trying. The first step is of course to build two 20m 1/4 verticals and match them as closely as possible. I’ll get into the spacing between the elements shortly.

After considerable research I came across the first design that looked interesting in “Practical Antenna Handbook” by Joseph Carr. The idea is to space the two elements at 1/2 wavelength and use a phase transform to switch between o° and 180° phase. The phase transformer is made using a 1:1 balun kit wired as follows:

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The switch changes the phase 180°. The arrangement give the following two patterns:

20171115_161737000_iOS 1A20171115_161737000_iOS

The only “gotcha” here is the 1/2 wave spacing is about 33 feet. My backyard may not be able to accommodate this due to a slope down to the resaca as well as some patio areas having pavers. A 1/4 would work much nicer but gives the following patterns:

quarter onequarter two

Not as cool but still workable.

The last option is two use 1/4 wavelength spacing and Christman Phasing. This technique uses lengths of feedline to provide the appropriate delays into each leg to provide for 0° and 90° phasing. The feed arrangement is as follows:

twin_vertical_relay_layout_spst_

For a 20m array using RG-8X cable having a velocity factor of 0.82 and at 14.20 Mhz, the 84° line should be 13.253 ft long and the 71° line should be 11.202 ft long. When both feed-lines are equal there will be a 0° case  and the pattern will be as follows:

quarter one

The 71° feed-line can be added to either leg and creates the following pattern (direction dependent on which leg it is added to):

90 degree

So these are my options, I’ll be measuring out the backyard and see what I can accommodate. Based on my QTH, I’d like to arrange the array to point to 45° with the directions as follows:

world

I’d like to start with the first arrangement but need to confirm I have the space.