Antennendraht

  • I agree with Rick. Frizel 1:6 Balun is a bad choice. I use like Rick recommended 1:4 and a Current-Balun. Wire is from DX-Wire FS2. The antenna is about 12m high and works fine.

  • Hi again Rick and Roger


    Thanks for coming back to my post and also for the directions/tips. By the way, I already joined the OCFD gtoup.

    OK on the bad performance of the Fritzel Balun, in fact I think it is just a transformer (S70 series). I want to build a 4: 1 current balun and for the wire I will give a try to the following options.

    DX-wire FS2

    Sotabeam's HD wire

    Aluminium fence wire with 1,8mm diameter (tensile strength of 75 Kg., very light and with good conductivity). I have a past experience with aluminium wire when I had a Lightning Bolt 2 element delta loop. The aluminium wire supplied with the antenna was welding wire. It was very difficult to form and to work with but never had an issue. Perhaps the fence wire is easier to form and has better mechanical properties.

    I read that someone in the group was going to give it a try. The fact is that it is quite cheap but you have to buy 400m rolls. No chance to buy 200m.

    I anybody has experience with the 1,8mm fence aluminium wire, I would appreciate any comments and pros and cons.


    72/73 de Vicenç

      

  • Hi Vicenç


    Pay special attention to the 4:1 Balun that you build. The balun is the most critical component in getting proper performance out of your antenna. There are lots of instructions on the Internet for building a 4:1 Current balun using just one single toroid. THIS DOES NOT WORK! A 4:1 Guanella balun MUST use two cores.


    In addition, a 4:1 current balun by itself is not sufficient for use in an 80m OCFD antenna. It does not have enough Common Mode Impedance. You will need an additional RF choke connected directly to the balun.


    Gud Luk with your antenna projects.


    73 - Rick

  • Hi Vicenç


    Pay special attention to the 4:1 Balun that you build. The balun is the most critical component in getting proper performance out of your antenna. There are lots of instructions on the Internet for building a 4:1 Current balun using just one single toroid. THIS DOES NOT WORK! A 4:1 Guanella balun MUST use two cores.


    Das trifft zu, ein 1:4 Guanella Transformator muss auf zwei Kernen gewickelt sein. Auf einem Kern gewickelt beeinflussen sich die magnetischen Flüsse der Wicklungen über den gemeinsamen Kern, was die gewünschte symmetrierende Wirkung degradiert. Eine meiner Meinung nach bessere Alternative für einen transformierenden 1:4 Balun-Transformator als ein Guanella ist ein Hybrid-Balun. Ein 1:4 Spannungsbalun wird zur Impedanztransformation benutzt, ein in Serie dazu geschalteter 1:1 Strombalun (aka Mantelwellensperre, Gleichtaktdrossel, Symmtetrieglied) übernimmt die Stromsymmetrierung. Jeder Kern macht das, was er am besten kann.


    Zum Thema gab es hier im Forum schon einen Thread

    Thread: Balun - Strom oder Spannung


    True, a Guanella Transformer needs two cores. Otherwise the magnetic fields of all Windings are cross-coupled. That causes a degradation of the desired Current Symmetry of the device. I prefer a solution called "Hybrid-Balun": a combination of an 1:4 Voltage Balun Impedance transformer and an 1:1 current Balun (aka common mode choke) connected in series. Each tranformer does what it is best suited for.


    Günter

    "For every complex problem there is an answer that is clear, simple, and wrong" (H.L. Mencken)

  • Hi Guenther, I don't know if Vicenç speaks German or not.


    The Hybrid balun is definitely the balun of choice for an 80m OCFD.


    In Spiderbeam's Aerial-51 Model 807-HD 80m OCFD antenna, I used a 4:1 Ruthroff (voltage) balun, together with a 1:1 Guanella (current) balun. This is the only way to achieve enough Common Mode Impedance to block all of the Common Mode Current when used in an 80m OCFD at typical city heights. If you can raise your OCFD 30 or 40m in the air, then the dual-core Guanella (alone) would probably be good enough, provided you wind enough turns on FT-240-43 cores.


    The 4:1 Guanella is constructed with two 1:1 Guanella baluns with their inputs in parallel and outputs in series. As such, their inductance are in parallel, which results in having only half as much Common Mode Impedance as with the 1:1 balun.

    This is why the 4:1 is insufficient in applications with a lot of CMC.


    For the Ruthroff, use 14 turns bifilar or twisted pair on an FT-240-61;

    For the Guanella, use 17 turns of coax (preferably Teflon-Insulated) on an FT-240-43.


    When stating balun ratios, we state it in the order of the name: BAL - UN.

    The ratio is stated with the value of the BALanced side first, then the UNbalanced side last.

    200 Ohms (balanced) to 50 Ohms (unbalanced) is stated as 4:1.


    73 - Rick

  • Moin,

    nun ist es passiert. Die Antenne aus #16 ist heute Nacht abgerissen.

    6 Monate Standzeit hätte ich dem dünnen Draht nicht zugetraut. Der Bruch ist an einer Scheuerstelle über einen Ast geschehen. Ich hatte zwar vor einiger Zeit entdeckt, dass der Draht auf einem Ast auflag aber nichts verändert. Bei freiem Hängen hätte der Draht wahrscheinlich noch weiter durchgehalten.


    Fazit: das Patchkabel gibt eine superbillige , für nicht dauerhafte Montage bestens geeignete, auf kleinstes Packmass reduzierbare Antenne ab. Daumenhoch


    73 Joachim

  • Das habe ich auch erlebt mit teuer Coax.

    Selbe schuldt! Ich habe es einfach ueber eine Ast gefuehrt, ohne ein Schutz.

    Ein ganz billig stueck Gartenschlauch haette gerreicht um es zu schutzt.


    Naechstes Mal wird alles besser! (hi)


    73 Rick

  • Moin,


    wer für die nächste Outdoor-Saison noch Anregungen für Experimente mit Drahtantennen sucht, findet auf der Seite von Martin (K0BXB) einige detaillierte Beschreibungen und Überlegungen zu seinen "Rucksackfähigen HF-Antennen". https://www.huyettm.net/portable-antennas.html


    Günstiger Draht ist ja vorhanden, so dass man über Winter ja mal eine oder zwei Varianten vorbereiten kann.


    73, Wolfgang

    DL2KI

    DARC: DOK K08 • DL-QRP-AG: #3247 • G-QRPC: #13541 • AGCW-DL: #3944 • HSC: #1970