Article Three – Tuning This the last article in my three part series of building a Home Brew, 160-meter, 3/8 wave inverted ‘L’ antenna and it will focus on the tuning of that antenna.
I left the reader last at
TXing and
RXing on 160-meters using my Yaesu 817nd at 5 watts. I eventually got out of the Faraday Cage my Kenwood TS-590S and put the antenna to the test. Although I received a bit better report on my signal than before, now using 100 watts, the reports were still no where near what I wanted this antenna to do. My goals could only be accomplished through the tuning of the antenna.
The VE of the New York club I belong too lives about a pistol shot away so I asked him if I could borrow his MFJ 259b antenna analyzer which he gleefully loaned to me. Once I picked up the analyzer I made my initial reading’s at the end of the coax in the shack NOT at the feed point of the antenna.
On Figure 1.1 we see the reading’s from inside the shack at the end of the coax. Figure 1.2 shows the reading’s taken at the balun feed point at the antenna. Please note that it was 8 degrees outside and my pen kept freezing so I only focused on 160 and 75/80-meters when I gathered the readings in Figure 1.2.
Date Dec, 27, 2017 Date Dec, 28, 2017
Freq R X SWR Freq R X SWR
1.900 2 6 17.2 1.900 35 210 17.8
3.800 70 57 2.5 3.800 65 60 2.6
7.250 10 21 5 7.250 0 0 0
14.275 14 22 3.7 14.275 0 0 0
18.170 53 26 1.5 18.170 0 0 0
21.300 59 64 2.5 21.300 0 0 0
24.990 33 29 2 24.990 0 0 0
29.000 18 14 2.4 29.000 0 0 0
1.1 Read in the shack at end of coax 1.2 Read at the Balun feed point
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I was able to use my Kenwood’s internal tuner to tune on all frequency's except for 160-meters. I made several contacts on 75/80, 40, 20, and 18-meters. However, 160-meters, my main focus for this antenna—The best I could attain was just be able to hover at above the noise level.
Scratching my head at this point I decided to solicited some help using eham.org
i. As always happens when you do this you open yourself to comments and advise that range across the spectrum of possibilities. After reading the cornucopia of advise several things came to light.
1) I needed more ground radials. One ham recommended 32, 50’ lengths of additional ground radials.
2) I needed to ditch the 4:1 balun and replace it with a manual tuner located at the feed point of the antenna.
3) Reduce the length of the antenna from 3/8 of a 160 wave (200’) to 1/3 of a 160 wave (175’) and another to 1/4 of a 160-
meter wave (133’).
4) Adding a capacitor to the feed point of the antenna.
In short, I decided to first add more radials. Second, order a manual tuner. While the tuner
ii was on its way, I added 8, 50’ radials for a total of eleven radials now on the ground.
Before the tuner arrived and after the addition of the radials I took some reading’s which I will share here.
Date Dec, 31, 2017
Freq R X SWR
1.900 24 203 >25
3.800 38 60 3.5
7.250 67 132 6.9
14.275 33 68 4.5
18.170 86 20 2
21.300 22 20 2.2
24.990 17 13 2.7
29.000 23 20 2.2
2.2 Read at the Balun feed point
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When compared to the reading’s I got as seen in 1.1 the addition of the radials improved R and X however SWR worsened. So the theory that was offered of adding more radials had merit.
With that written It was becoming more and more apparent that my goal to have an antenna that was used for more frequency’s than 160meters was quickly waning. The big test was going to come once the manual tuner arrived which finally did on January 2, 2018.
While waiting for the delivery of the tuner I took a piece of 1/16 x 3 x 5” piece of plexiglass and cut a hole in it to receive a SO 239, 4 hole chassis mount in anticipation of using a jumper cable from the connector to the tuner after attaching the antenna and ground wire to the connector. Here are some pictures of the end result.
2.3 and 2.4 SO-239 4 Hole Chassis
Once that was accomplished I needed something to put the manual tuner into that would protect it from the elements. I had a spare plastic 5.56 Nato ammo can that was just collecting dust and screaming to me, “use me...use me” which I did.
Drilled two holes in the can—One sized for the jumper coax cable and one was sized for the RG-213/u coax cable.
Well a day or two after the manual tuner arrived it was time to hook everything up and see what the readings were once the antenna was optimally tuned to the antenna.
2.5 Finished Product
The final optimal reading’s at 1.900 Mhz was: R = 27, X = 0 , SWR = 1.7. Okay, not perfect however much better than what I was dealing with before disconnecting the balun and adding the tuner.
In the shack I took additional reading’s at the end of the 100 feet of RG-213/u coax cable and the reading’s were: R = 87, X = 17, SWR 1.9. Well within the ability to tune using my Kenwood’s internal tuner.
That night I made six contacts on 160-meters. All contacts gave me 5/9’s and raved about my signal. Since then when propagation allowed, I have made contacts from as far NNE as Nova Scotia WNE to Wisconsin, SSE to Louisiana, and SEE over to northern Florida and all in-between.
As a side note, I love 160-meters! There seems to be less noise than I was expecting and much less than some other frequencies. The disappointment is that I can not presently use this antenna for some other frequency’s.
Once the snows melt and it becomes a bit more habitable outside, I will do the following:
1) Add additional radials as was suggested by one ham from eham.org.
2) Hookup wire jumpers from before the SO-239 Chassis to the balun and then a jumper from the balun to a manual switch then
the coax so I could bypass the tuner and go from the balun direct into the shack and work the other frequency's with the
tuner out of line.
3) I have the ability to raise the antenna another 30 feet which will put it at about 130 feet high or 1/4 wave length above terra
firma. It will involved the removal of some branches in trees that lay in the antenna’s path.
4) Last, I would like to learn how to use the 4nec2 antenna modeling software to see what I am putting out on all of my
antennas.
With the 160-meter antenna project done until the weather clears. Now it is time for me to start on my NVIS antenna project. If there is an interest I will post my trials and tribulations on that project too.
73
Footnotes: i—
e.ham.org thread ii—
MFJ Tuner
