Tag Archives: 1/4 wave vertical

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:

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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.

 

Working Asia on 40m FT-8 & JT-65

Band conditions on 40m to Asia have been quite good the past few days. Generally good conditions in Japan especially after 7:00 am until about 8:30 am local time. Here is my PSKreporter spots page after a few minutes of sending CQ DX this morning:

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Nice ring of stations hearing my FT-8 signals starting in Hawaii then on to Figi, New Caledonia, Australia, Indonesia, South Korea and Japan. Also notice the density of signals on the waterfall. So many stations working FT-8 that there are increasingly few open areas to park in.

In contrast JT-65 is increasingly quiet. This is actually an advantage in tha the stations that are there can pick up my signal easily with little effect from nearby strong stations. here is my JT-65 map:

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I am starting to get used to the pacer of FT-8 and today found the longer time on JT-65 a bit tedious. I guess it is hard to change gears and accommodate a different rhythm of QSO’s.JT-65 is definitely more relaxed now that there are fewer competing signals.

I continue to be very pleased with the performance of the 40m 1/4 wave vertical.

Working the CQ WW SSB Contest on the ICOM 7300

I was on a short business trip to China last week and arrived back home late Friday night after the CQ WW SSB contest had already begun. I started working the contest after lunch on Saturday using the Icom 7300 on 100W and with the N1MM logging program. I took a little time before starting to enable the spectrum display feature on the logging software as well as the spotting capability. This was fairly straightforward and only required that I change the baud rate on the rig. How did this all work? Well all I can say is I wished I had this in earlier contests! Here is a view of my contest screen:

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Spots match up with the spectrum display and a simple click on the signal of interest adjusts the rig. There are screens that display the spots that will maximize my score which is really handy. I operated search and pounce on 10m, 15m, 20m and 40m bands. Here is a summary of my score:

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Action on the daytime bands was centered on 15m. There was some intermittent activity on 10m during daytime hours. 20m was very active but also seemed difficult for me to make contacts. Not sure if this was related to the antenna or propagation conditions. 40m at night was also quite active with very decent DX. Overall a good cross section of DX with 63 DX entities contacted over 35 CQ zones.

Lots of fun with this and a good test of the vertical antenna system.

 

Practical Application of Soil Measurement Data

Anyone interested in ground radials, ground mounted verticals and even elevated radial verticals should visit Larry Severns, N6LF, website. he has done extenstive research om the subject and has published his results in QST and QEX with many of these articles available on the website. His article ” Experimental Determination of Ground System Performance for HF Verticals Part 4 How Many Radials Does My Vertical Really Need?” was originally published in QEX May/June 2009 edition. The following graph was taked from this paper:

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This graph shows the change of signal improvement on a 1/4 wave vertical with 1/4 wave ground radials under different ground conditions. The impact of this graph is that when the ground is “good”, adding more radials results in small signal improvement vs when using a “poor” ground. I can expect a .2dB improvement if I double my radials from 8 to 16. If I double again to 32 radials my signal improvement would be only around .5dB.

There is a real economic benefit to having good soil as in general fewer radials are needed because the ground losses are less than when over poor soil.

More on Soil Meaurements

It is extremely easy to take soil electrical data using the RigExpert by running a frequency sweep. This sweep is saved on the meter and then transferred to the PC and exported as an CSV file. This file contains impedance measurements across the sweep range. Add the formula to convert to conductivity and Er and you get the following graph:

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This data was calculated with a Co = 8 pF adjusted after making a few more measurements. The average values per band are as follows:

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The values above can be compared to those given as standard values in EZNEC. I further compared the gain results when using a 40m 1/4 Wave vertical with four ground mounted radials as follows:

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In this case, the model has a 2.27dB difference in measured gain between the average soil case and the measured reading. In practice, using the “Very Good” values will likely be close enough for modeling work here at the QTH.

 

Measuring Ground Properties at the QTH

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.

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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:

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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

ICOM 7300 – First Impressions

I spent some time playing with the new IC-7300 transceiver this weekend on various modes. My first comment is that having used an IC-7100 for some time I was instantly familiar with about 90% of the IC-7300 controls. Most of the buttons are labeled the same and many of the setting menus are also the same. First thing I installed was a headset adapter so I can use the Koss SB-45 headset. I needed a plug adapter (which I luckily had on hand) to plug in my Vibroplex paddles. Rig control via Ham Radio Deluxe was fairly straightforward as the USB drivers are the same as the IC-7100.  I started operating on 20m during the North America QSO party on Saturday with the 1/4 wave verticals.

My first impressions are that the rig works well (and possibly better) than the IC-7100 on SSB. My signal reports were solid 59’s and occasionally 59+ all across the USA. Also made some DX with favorable reports.  Receive options make it easy to adjust RF gain controls and filters to help clean up the signals. I like the overload indicator which tells me to back off on the preamp or RF gain or both. The main learning curve for me thus far is in using the scope screen. Once you play with this awhile you get used to operating more visually. You can see whats going on across the whole band and find signals to tune into or find dead spots where the frequency is open. It is also easy to switch in the audio monitor to hear what you are transmitting.

Also tested digital modes JT-65, FT-8 and PSK31 after configuring the software for the rig. The audio scope helps look at the signal quality on digital modes. I did not find any notable differences in using the 7300 vs the 7100 on digital.

So overall I am impressed by the new rig especially on SSB Phone. I’ll likely expand on this review as I get some more time on the rig but I am happy with what I have seen thus far.

The IC-7100 is now setup as my base VHF/UHF rig and I hope to play with DSTAR on it for the first time sooner rather than later. I will continue to have it connected to my PC for rig control and can switch in HF when needed.