Summer HF Antennas

I took advantage of the small Easter vacation last weeks and installed two HF antennas at our countryside place, 10 km away from the city, where I spent most of the summer weekends. Like every spring, I reinstall my wire antennas in the big old cherry tree just before the leafs start to grow and make this job difficult. Except adding some masts, I cannot install hinged antennas in the courtyard other then the trees.

Dipole for 20M band. A 2 x 5 m Inverted V, with feed point at about 7-8 meters high.

I made this antenna first time in the same location two years ago. Worked fine JA and K with 5W. Last year I did a butterfly dipole, adding also a 2 x 10m of wire for the 40m band. I wasn’t very satisfied on 40, not so spectacular DXs. On 20 and 15, on the other hand I made my first South American contacts. Don’t know if the extra 2 x 10 m counted to much, but this year I decided not to add it anymore.

Dipole for 20m Band - 2x5m

Dipole for 20m Band

Quad Loop for 10M band

From the remaining wire I took one side of 10 m long and made this quad loop, vertical mounted, for the 10 M band. Each side is equal, aprox. 2.5 m each, hinged from a walnut tree.

Quad Loop Antenna for 10M Band

Quad Loop Antenna for 10M Band

Normally a quad loop has 100 ohms impedance, so I made a 2:1 balun. I could have live with that, and made the LDG Z-817 tuner do the job, but at my FT-817 having the extra BNC socket in the front panel I wanted to easily switch between the dipole (connected with Z817) and the Quad Loop (already tuned).

2:1 balun quad delta loop

2:1 Balun

I used an Amidon T130-2 toroid for the balun, and wired, like in the diagram below, 6+6+6 wounds. Didn’t made any fancy box for it, just wrapped insulating tape all around.

2:1 Balun Wiring

2:1 Balun Wiring

Here is the loop being measured and marked the corners before putting it to its place in the tree.

Quad loop antenna 10m band

Quad Loop Setting Up

Hope this small walnut tree branch to be able to hold the antenna this summer 🙂

Quad loop 10m

Antenna hanging from the wallnut

Now waiting for the 10M season to arrive. Didn’t made any QSO yet with it, just a comparison when receiving between this and the dipole. The difference is quite remarkable. More noise silence and more gain, although in theory I found out that a vertical loop has about 1.2 dB gain over a dipole.

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3 Responses to Summer HF Antennas

  1. Salut,

    loop-ul pentru 10m e o antena foarte interesanta, vezi ca ii poti aduce impedanta in jurul a 50ohm doar din forma, mai exact din raportul dintre diagonala mare si cea mica a rombului format. Alta chestie de stiut (probabil ai observat-o si practic) e ca pentru o bucla inchisa lungimea rezonanta e cu aproximativ 5% mai MARE decat lambda. Obligatoriu alimenteaz-o in coltul de jos si ridic-o cat de sus se poate, afecteaza mult performanta.

    Razvan.

  2. Adrian says:

    Salut Razvan,

    Da, e posibil sa fie mai scurta. Am folosit cred ca ~10.5m de cablu. O sa pun si un analizor pe ea sa vad mai exact unde rezoneaza. Fara balun aveam vreo 3 liniute SWR la FT-817, si cu un SWR-metru mai ieftin de CB imi arata putin peste 2:1. Cu balunul acum pe FT-817 nu e nici o liniuta la SWR…bine, stii si tu, SWR-metrul de 817 nu e o referinta prea buna, doar asa ca idee.
    Eu am facut cam aproape patrat. Acum, nu stiu, daca se aproprie mai mult laturele intre ele, nu isi micosreaza si gain-ul? Din cea am citit, loop-ul rotund ar avea cel mai mare gain,
    Ce nu am gasit info mai clar e legat de directivitate. Eu o am orientata N-S, si cam 30 deg spre E, mai exact N-NE – S-SW si nu stiu cat de mult ar conta.

  3. Salut,

    intr-adevar scade putin castigul si rejectia laterala, dar s-ar putea sa fie niste scaderi mai mici decat pierderile in balun. Daca tin bine minte, trebuie sa comprimi putin rombul pe axa orizontala, astfel ca diagonala verticala sa fie mai mare decat cea orizontala, pentru a scadea impedanta. In simulare rejectia laterala e de ~11dB (deci aproape 2 grade S reale, nu de-alea ale lui FT-817 care are si 1dB per grad S in unele portiuni ale scalei) deasupra unul sol mediu si cu baza la 5m inaltime, iar din practica iti pot spune ca se simte destul de bine, mai ales cu 5W o sa vrei neaparat sa intorci antena pe directia de interes.

    Razvan.

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