The Portable Windom Vertical, VCH アンテナ

2009/08/06            日本語は下にあります


Subject:   “The portable windom vertical antenna”   VCH アンテナ」


This antenna was designed and developed by JP6VCH, S Matsuki, primarily for the portable outdoor use such as camping, hiking, fishing trips, and cycling etc.  It is popular among the Japanese hams.  I came across this antenna in internet but not known among the north American hams and nothing was described about this antenna in English.  So I am up-loading the information.


I have homebrewed one last winter for my winter project and the final tuning was made this month, August.  The antenna was designed primarily for 40m band but it can be a multi bander using a tuner and changing the coil inductance with taps provided.  I suggest click in “Google” and type in “VCH antenna” so that you will see more than a dozen of websites.  The problem is all in Japanese.  NO WORRY, there are lots of pictures shown, however.  Please watch carefully those pictures to see and understand the shape, material used, operation, tuning and adjustment etc.   It is all there for you to watch to get the general ideas.



My recommended way of homebrewing:

The key part is the coil to make.  I suggest get a B & W air inductor such as 2 1/2 in dia, 14AWG wire for 30 turns in a hamfest or in your shack somewhere.  The coil requires 32 micro henries to 34 micro henries.  Mine is 37 micro henries after homebrew, Hi.  The rest of parts are wires and connectors for your choice and ideas.  You use your own design to put together and make one.  I bought a golf ball retriever, 15 feet long, from the Walmart for 12 dollars Canadian to lift the antenna up.  I up-loaded a sketch of the antenna by JP6VCH and some pictures of my antenna on the album of this blog, Portable Windom Vertical, August 9, 2009, for you to see.



The measurement:   (by MFJ-259B antenna analyzer)

Freq (Mhz)    SWR   Impedance ohms     R      X

7.000          1.4     70                  72     8

7.050          1.5     75                  75     12

7.100          2.2     90                  78     49



The Coil making:

I homebrewed the coil required.  The coil form is an emptied 500ml water bottle, 2 1/2 in dia. and 7 in long from the shoulder to the bottom.  The wire I used is AWG #15.  No. of turns = 35 turns over 5 inches that is 7 turns per inch.  The coil is 37 micro henries achieved.

I used four pieces of wooden chop sticks and I marked 35 lines evenly then made slight grooves on the marked lines with a hand metal saw on all four chop sticks so that the wire will sit on the grooves to make a coil.  Then I glued the chop sticks with contact cement at 1/4 position on the circumference of the bottle.  See my pictures to get the idea.

The tap location :

Install about one foot long wire at the top of coil with an alligator clip.

7Mhz     Use all coil., no tap

10Mhz    a tap on 11 to 12 turns from the bottom

14Mhz    a tap on 5 to 6 turns from the bottom

21 to 28 Mhz   The wire with an alligator clip be connected to the bottom of the coil.

All you need is to have a coil of which inductance is about 34 micro henries or so.  You do not have to homebrew this coil if you get a B&W air inductor as I said earlier.



Assembly and dimensions:

                               My antenna                 JP6VCH

The upper element       1.1 meters long          1.4 meters long

The coil                 37 micro henries         34 micro henries

The lower main element  3.4 meters long          3.4 meters long

The ground element      5.2 meters long          5.2 meters long



The Tuning:

The designer, JP6VCH, recommends use a fiber glass fishing rod, about 5 meters long.  I do not have it and I used a golf ball retriever, 15 feet long, aluminum rod.  The rod is metal and not ideal material for this vertical antenna.  I used the rod for only lifting up for 15 feet up in the air.  The rod is set up with some angles so that the wire of the antenna will hang straight down, not along the metal rod. 

I used the MFJ-259B antenna analyzer.  The upper element was cut at about 1.7 meters long initially.  And I cut the upper element down to 1.1 meter long so that the antenna was achieved at the resonant frequency of 7.000 Mhz.   As you can see, this antenna will be used outdoor for one activity, then it will be disassembled.   Therefore the SWR will be slightly changed from one place to another depending on the set up situation.  The designer recommends use a tuner to overcome the problem and also the tuner allows you to go on multi-bands. 


Antenna configuration (Use a tuner as required)

FREQ.      upper element     coil         lower main element   ground element

7 mhz       no change      full inductance    no change          5.2 m

10 mhz      no change     10mhz inductance  no change          5.2 m

14 mhz      no change     14mhz inductance  no change         2.6m (1/2 x5.2 m)

21~28 mhz  no change   no coil, skipping coil   no change         2.6m (1/2 x5.2 m)



The ground element and the conductivity:

The ground element will be placed on the ground, namely a concrete surface, grass and soil and sand etc.  The conductivities of those differ because of the moisture level and the nature of the materials.  The resonant frequency and SWR will be changed due to those factors. 



Testing and Operation:

This antenna is recommended for use up to about 10 watts.  Above 10 watts it can be used but I have not tried.  Some hams in Japan claim up to 50 watts without any problem.  You can modify and up-grade so that it cab handle 100 watts with heavier materials.


On August 5, 2009, I went on air for test on 40m band and have made two QSOs.

N4 LQ,  Steve,  his 579 and me 239   He said QSB and a bit QRN, copy hard.

N9EP/2,  Ed,     his 359 and me 539   Ed was running QRP.

My rig: Yaesu FT-817  pwr 3 watts


JP6VCH claims that the pwr from the antenna will be radiated towards the extended direction of the ground element.  During my test QSOs, I did not notice any deference.  I am happy with the performance of this antenna and I look forward to using it for the rest of this summer.






In Japanese

VCH アンテナ」


インターネットでVCHアンテナのサイトがあり、必要なデータ-を集め、200812月から20094月にかけ、一つ自作しました。 日本ではCQ誌にも掲載され、皆さんは良く知っていると思いますので、詳細はそちらを見てください。


コイルの自作: 一番手がかかるのはコイルと思います。 出来上がってテストで使ってみると、いちばん簡単なこちら流のやり方は、B&W社の出来合いのコイルがあり、これを使うのが確実で、簡単と思いました。 後はワイヤーでつなげればよく、調整は私の場合は、MFJ-259Bを使って上部エレメントを短く切り、7Mhzに同調を取りました。


木の割り箸を利用し、約35巻きできるように、等間隔でしるしをつけ、カナノコの葉で軽く溝をつけ、巻いた時に銅線が溝に座り動かないようにしました。 割り箸をコンタクトセメント(セメダイン)で空き瓶にしっかり止め、最後に銅線を巻きコイルを作りました。



釣竿: 日本では手ごろな釣竿が売っているようですが、私の家は田舎にあり、手に入りませんので、町の店から、水の中に落ちたゴルフのボールをすくって、拾い上げる「リトリーバー」4.5m を1200円くらいで買ってきて、代用しました。 細いアルミのパイプが伸縮するようになっているので、アンテナのワイヤーをパイプに絡ませるわけにいきません。 傾斜をつけて立て、テュ-ナーとヤエスFT-817 パワー3ワットをつなぎ、テストを兼ね、オン エアーしました。


85日、N4LQN9EP/2 の2局と交信でき、239539をレポートとしていただき、テストを終わり、この夏あと1ヶ月か1ヵ月半は外で使えるので試してみる予定です。


私のこのブログのアルバム、200989日「Portable Windom Vertical」に写真を載せましたので見てください。 VCHアンテナではこちらでは意味がわかりませんから、 Portable Windom Vertical Antenna と呼ぶことにしました。 また、質問があればメールをください。



ひろ はやし VE3CGC


This entry was posted in ハム ラジオ、アマチュア無線、ham radio, amateur radio. Bookmark the permalink.

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