Many radio amateurs do not have the space to implement full-size antennas. Compromises are necessary in a smaller space. It is offered the possibility to implement a rotary direction on 10/15m, but since the bands are mostly closed and the allocated frequency segments did not appeal to me, I was looking for an antenna primarily for the lower bands.
Jirka OK5IM ponúka mulitband KV vertikál with a radiator height of 13m. The problem with vertical antennas is the radial system. I didn't want to dig up the garden, and the raised radios would have to be very close to the telephone wires and they wouldn't fit in the garden at all. Nevertheless, this antenna can be very interesting, see. http://ok5im.com
Setting up shortened antennas requires experience, time and measuring technique. Measuring the distance between the skylight and the tree showed only a distance of 21 m. What to this space? A single-band inverted L antenna was offered, but it would require burying several radials. Out of "laziness" I started looking for a horizontal antenna on the Internet. Surprisingly, there are not many constructions. During one such search I found an antenna Diamond W-8010, ktorú predáva na Slovensku firma AWAS, viď. http://www.awas.sk . And it was decided.
Anténa je určená pre päť pásiem: 10m, 15m, 20m, 40m a 80m. Využíva dva žiariče s trapmi so spoločným napájaním cez balun. Its length is approx. 19 m, weight 2.5 kg. The load capacity is 1.2 kW. Potrebné je mať dva body v požadovanej výške vzdialené od seba minimálne 20m a ďalšie dva body nižšie na zošikmený žiarič.
The top radiator is for the 80m, 40m, and 15m bands, the bottom, slanted for the 20m and 10m bands. Tuning is done at working height from the shortest band to the longest by shortening wire elements at traps. The advantage is that tuning each band in this way does not affect others.
The antenna is supplied in a thick double-helit package that contains everything needed. You may need more nylon rope (for hanging the antenna) and a few additional tie-down straps. The problem was the manual, which was only in Japanese. Fortunately, an English version of the manual is available online.
After pulling the antenna to working height, tuning is necessary. In the manual, you will find how much frequency change shortening an element by 1cm will cause on a given band. Because after antenna installation, all elements have full length, the antenna will resonate below the bands. In my case, the resonant frequency on 10m was 27.45 MHz, and the other bands were also very low.
Bandwidth for PSV do 1,5 je: na 10m 500kHz, na 15m 400kHz, na 20m 100kHz, na 40m 60kHz a na 80m 24kHz (podľa manuálu). Zrejme vplyvom strát koaxiálnom kábli je šírka pásma na 80m až 45kHz (podľa PSV metra MFJ aj TCVR-a). Je však možné, že na šírku pásma má aj vplyv prostredie v ktorom je anténa inštalovaná.
Tuning requires patience and a thoughtful way of raising and lowering the antenna. I had to hang a pulley on a tree (birch) as a climber because climbing a birch without branches is not something for radio amateurs, HI. Tuning took about three hours of actual time because after shortening the radiator, it was necessary to pull the antenna back, go to the station, measure PSV, and launch the antenna again. Since I tuned the antenna to SSB segments, on 80m, just shortening the element was not enough; it was necessary to move the end insulator by 15cm to make the antenna shorter.
Of course, the most important thing is whether the antenna is working or not. And this is the area where the Diamond W-8010 shines. Napriek tomu, že som mal obavy predovšetkým o pásmo 80m, anténa chodí na blízke aj DX vzdialenosti výborne. Presadila sa v OM Activity conteste, Plzeňskom poháe a zopár EU DX na 80m. Žiaľ, napriek tomu, že som počul niekoľko JA staníc, nemal som možnosť ich zavolať. Na vyšších pásmach počúva dobre, segmenty triedy N sú však prázdne, takže otestovať na DX sa mi ju zatiaľ zodpovedne nepodarilo. Potešujúce je, že som nezaregistroval TVI ani u mňa, ani u susedov (výkon 100W). Anténa je pre okoloidúcich takmer neviditeľná.
The negative aspect of the antenna is that it is sensitive to rain and snow, which cause a shift in the resonant frequency (approximately 1 - 1.5% downwards).
The Diamond W-8010 pleasantly surprised, the antenna works very well and helped to solve the complex issue of fitting the antenna into a small space.