Tag Archives: 1/4 wave vertical

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.

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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.

WSPR Data collected from the 20m Hamstick Vertical Dipole

Here is 24 hours of WSPR data collected from the 20m Vertical Dipole:

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There were 114 unique receive spots and 90 unique heard from spots with 1W transmit. This seems low compared to N5Cey’s 20m 1/4 wave vertical which typically receives 180 to 200 unique spots from his QTH near Los Fresnos.

I did some A vs. B tests on SSB yesterday switching between the 1/4 wave vertical and the vertical dipole. This time I used a remote receiver using Websdr.org. I connected to a station in the San Fransisco area and monitored my voice transmissions. In this case the vertical dipole came in about 1 S units stronger. I then switched to a station in New Jersey and the opposite was true!

I am going to do some additional testing on various 20m vertical configurations using WSPR over the next couple of days.

My Ugly Balun

I built an ugly balun today to try and address the SWR swings I was getting on 20m. It actually went together in about 10 minutes. To build it I used a 4″ PVC pipe coupler as a form. I drilled two small holes to run a tie wrap through to hold the end of the coax in place. I had a 25 foot piece of RG-8X laying around with PL-259 connectors on each end. I wrapped 15 turns around the coupler and then tied it off the same was as the other end. Some long tie wraps then are used to hold the winding securely on the form. I replaced the 1:1 current balun I had been using with this. To match up the coax connectors I used two bulkhead connectors and wrapped with electrical tape (for now). Here’s what the finished balun looks like:

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And here it is installed at the vertical antenna feedpoint:

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The balun seems to help with the SWR issues on 20m but I see some shifts in the overall SWR response. I’ll likely have to tweak that over the next few days.I have some ferrite toroids on the way as well and will try and build a choke with those as well. Signal reports on both 40m and 20m SSB were real good tonight!

 

What’s Better than One 1/4 Wave Vertical? —How About Two?…

Next experiment in vertical HF antennas is trying a 1/4 wave vertical “fan dipole”. The 7.2m fishing rods are a perfect support for up to a 20m wire radiator. I set a length of 3/4″ PVC pipe about a foot away from the existing 40m 1/4 antenna. I also removed the last two section of fishing pole as they are too flimsy and are not needed length to support a 20m wire. I connected this wire to the point where the 40m wire connects and after a bit of tuning had three dips in the SWR. 7 MHz is the main tuned frequency, 14 MHz is the new radiator and 21 MHz is the third harmonic of the main radiator. Here is the SWR plot:

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Here is what is looks like:

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So far this works well as before on 40m and 15m. The performance on 20m looks a little shaky still as I am seeing my SWR swing around a bit when transmitting. This indicates to me that my feed line is picking up RF at that frequency. I’ll be building an Ugly Balun soon to try and clean that up. The antenna hears very well on 20m with very little noise so I f I can solve the SWR issue I should be in good shape.

 

Working 40m and 17m this Weekend

I reconfigured what has become my main antenna, the 40m 1/4 wave vertical. This is still a temporary installation but I am growing increasingly happy with the results I am getting. I frankly can’t remember the last time I used the horizontal end fed. I have had to roll up the radials on occasion to mow the yard and have not yet deployed my permanent radials. Currently I am using the 30 foot travel mast from SOTAbeams to support the vertical wire and have four 27 foot radials deployed. I am using my homebrew 1:1 current balun at the feedpoint and running to the shack with 50 ft of RG-8X.

If I get the chance I’ll start operating around 6:30 am local time on 40m JT-65. I can usually snag several contacts in Japan with the occasional contact into Australia, Indonesia or the Philippines. The action is over by about 7:30am local time as the band closes quickly after sunrise.

Saturday afternoon, I was checking the bands and came across a strong VK station on 17m SSB. We exchanged signals reports in the 54 to 55 range. I moved over to JT-65 and found that there was DX activity including another VK contact. Today Sunday I am finding about the same conditions, great 40m propagation to the far east in the early morning and some light DX into Europe & South America on 17m in the late afternoon.

 

Vertical Weathers a Thunderstorm

We had some much needed rain at the QTH last night. I had taken down to work on the Homebrew Buddipole early last evening but left the 40m vertical in place. The storm blew through at about 4am and dropped over an inch and a half of rain with gusty winds up to 25 Mph. My wife went outside early this morning and came in to tell me we had debris in the back yard and oh by the way your antenna is bent. Doh!

Went outside expecting the worst. I have heard stories of fiberglass tubes breaking off in high winds. I was relieved to find that the antenna was indeed bent near the top, but only because the vertical wire had blow into and tangled into a tree branch holding it over. I shook it loose and it popped back vertical instantly. Three sections had telescoped back in near the base so after pulling them back out I am back in business. This SOTABeams travel mast has taken some real abuse!

40m QSO’s with 1/4 Wave Vertical

Most of this week was sent collecting WSPR data on the 40m 1/4 wave vertical. The vertical is holding up better to the breezy days after placing some duct tape on the joints of the travel mast. The vertical radiator is a 32 foot length of insulated #14 speaker wire. There are only four 27 foot ground radials deployed at this time. There is a 1:1 current balun at the feed point and about 50 feet of coax to the shack after that. Here is the SWR plot:

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SWR is under 1.5:1 across the whole band with a resonant point 7.125 MHz. This antenna has been a solid performer on 40m without a tuner. I am noticing that the band starts opening up to DX about an hour before dusk. Last night I made several SSB contacts with Europe after 10pm local time.

Switching to 40m JT-65 at that time was very interesting as well  as the propagation conditions can be somewhat visualized with pskreporter. I really tested the JTDX software last night and have gotten the hang of the user interface which is subtly different from WSJT-X.  I set the IC-7100 with AGC-off and the bandwidth filter set to 3.6 kHz. Rather than search and pounce, I would look for a quiet spot at the extremes of the band and call CQ DX. This strategy worked well with many European stations answering. Over time, I can see my signals fading on the pskreporter map as eastern Europe’s morning progresses. As dawn approaches in Western Europe, stations start coming online and start to see my signal. At the same time, the opposite terminator starts approaching New Zealand and Australia and my signals starts picking up there as well. I knocked off at about midnight local time and picked up at about 7am and repeated. This time JA stations were answering my CQ and I was running a JT-65 “pile-up” with several JA stations calling at the end of a QSO.

Very pleased with the antenna performance on this band. 20m is acceptable through a tuner but the WSPR data indicates some degradation in performance over a resonant vertical or even the end fed antenna.