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Tema: Anteni:yagi,Gp,Dipol.Jpole...

  1. #1

    Anteni:yagi,Gp,Dipol.Jpole...

    Yagi
    Specifikacija antene
    Rezonantna frekvencija antene: 145,350MHz (simpleks kanal S14);
    Dobitak na rezonantnoj frekvenciji: 6,2dBi;
    SWR na rezonantnoj frekvenciji: 1:1;
    Impedansa na rezonantnoj frekvenciji: (50+j0,09)Ω.
    Mere
    Mere elemenata su date u sledećoj tabeli:
    Rastojanje između elemenata je 358mm.
    Karakteristike
    Dijagram zračenja na rezonantnoj frekvenciji u vertikalnoj ravni:<br/>
    2m_2elem_yagi03.jpg"2m_2elem_yagi03.jpg"2m_2elem_yagi03.jpg
    Dijagram zračenja na rezonantnoj frekvenciji u horizontalnoj ravni:
    "2m_2elem_yagi04.jpg"2m_2elem_yagi04.jpg"2m_2elem_yagi04.jpg
    Impedansa na rezonantnoj frekvenciji:
    SWR u funkciji frekvencije:
    "2m_2elem_yagi02.jpg"2m_2elem_yagi02.jpg"2m_2elem_yagi02.jpg
    Impedansa u funkciji frekvencije:
    "2m_2elem_yagi01.jpg"2m_2elem_yagi01.jpg.2m_2elem_yagi01.jpg

  2. #2
    U posljednjem broju prikazao sam gradnju 12 elementne verzije antene za 2 metarsko podrucje po dimenzijama koje je proracunao Njemacki radioamater DK7ZB. Kako svi radioamateri nemaju mogucnosti i uslove za postavljanje velikih antena u ovome clanku prikazati cu izradu 6 elementne verzije istoga autora, koja se pokazala kao dobar kompromis izmedju pojacanja i duzine same antene. Ideja kojom sam se vodio pri izradi je bila izrada lagane antene sa dobrim mehanickim karakteristikama, cistim dijagramom zracenja i maksimalnim pojacanjem koje mozemo dobiti koristeci navedenu duzinu booma. Posebna paznja je posvecena materijalu koji se koristi pri izradi, u konkretnom slucaju, aluminijski profili i elementi starih televizijskih antena, a da se time ne naruse same karakteristike antene i osigura ponovljivost izrade iste. Kao rezultat sam dobio cijenom jako povoljnu antenu za ciju su gradnju iskoristeni elementi, boom, izolatori, starih televizijskih antena koje su sve vise dostupne dolaskom nove satelitske TV tehnologije. Sve sto smo naveli za gradnju 12 elementne verzije moze se reci da vrijedi i za ovu antenu, naravno uz promijenjene dimenzije i broj elemenata.
    <br/>
    "image003.jpg"image003.jpg"Prilog 40
    Osnovne karakteristike:
    Broj elemenata: 6
    Duzina antene: 2,40 m
    Impedancija napajanja: 50 ohma
    Pojacanje: 9,9 dBd
    Odnos naprijed/nazad: 24 dB
    <br/>
    Pri ovoj gradnji jos jednom smo za zraceci (Radiator) element koristili otvoreni dipol impedancije 28 ohma sa prilagodnom sekcijom na 50 ohma. Ovakav nacin prilagodjenja se pokazao iznimno dobar jer je lagan za izradu, odlicnih mehanickih karakteristika, izlazne impedancije 50 ohma te je podesavanje antene svedeno na "trimovanje" duzine radiatora za odredjeni dio 2-metarskog podrucja. Prilagodna sekcija se izradjuje od koaksijalnog kabela impedancije 75 ohma i to na nacin da dvije dionice cije duzine dobijemo pomocu formule L=lambda/4 * V spojimo paralelno na oba kraja dionice kao sto je i pokazano na slici 2.
    Bitno je naglasiti da duzina dionice osjetno ovisi o faktoru skracenja V koaksijalnog kabela te ona varira istovjetno sa vrstom i kvalitetom kabela kojeg koristimo. U tabeli 1 mozemo usporediti razlicite tipove 75-omskih kabela sa pripadajucim V faktorima skracenja.
    Tabela 1 Tip kabelaV faktor skracenja Vrsta izolacije
    RG-11-0,66PE
    RG-59-0,67PE
    RG-187-0,695PTFE
    RG-179-0,695PTFE
    RG-302-0,695PTFE
    Sat TV0,82PE
    Mnogim ce graditeljima vjerovatno biti najdostupniji SAT-TV kabel cija impedancija zna dosta odstupati od nazivnih 75 ohma te faktora skracenja V=0,82. U tome slucaju duzina prilagodne sekcije L= 425 mm. Preporucuje se koristenje kvalitetnijih, mada ce i ovaj kabel zadovoljiti potrebi. Problemu odredjivanja pravilne duzine moze se doskociti tako da se na jednu stranu prilagodne sekcije paralelno spoje 2 otpornika od 56 ohma rezultirajuci otporom od 28 ohma koji bi trebao predstavljati radiator. Na drugu stranu spojimo signal iz predajnika te pomocu SWR-a, kracenjem ili produljenjem dionice osiguramo najmanju povratnu snagu. Takva je prilagodna sekcija spremna za spajanje na dipol i preostaje nam samo podesavanje duzine dipola za odredjeni dio 2 metarskog podrucja. Istim postupkom se mozemo posluziti u slucaju odredjivanja duzine prilagodjenja a da ne poznajemo V faktor skracenja 75 ohmskog kabela.
    Radijator – dipol antene montiran je na boom uz pomoc elektroinstalacijske kutije kao na slici 3, ali se u istu svrhu moze iskoristiti stara spojna antenska TV kutija. Polovice dipola su u tocki napajanja medjusobno razmaknute 10 mm i izolirane plasticnim izolatorom u sredini. U oba slucaja, uzemljenje-masa koaksijalnog konektora mora biti galvanski spojena sa boomom same antene<br/>
    Tabela 2: Osnovne dimenzije, mjere u mm, elementi 10mm promjera Elementi 10mm dia.
    Reflektor Radiator Direktor 1 Direktor 2 Direktor 3 Direktor 4Udaljenost
    0 390 =640= 1150= 1785= 2380
    Duljina 1017 =971= 935= 907= 905= 876

  3. #3
    144MHz 2m Portable Yagi VHF Beam Antenna


    Version 4 of the portable beam, the ‘PegTenna’!

    This page contains construction details on a 2 metre 144MHz VHF Yagi beam antenna, designed for portable use. Since an old 5 element version (v1) of my antenna was shown in the July 2011 edition of RadCom, a few people have contacted me asking for some information on how it was constructed. It has gone through a few revisions over the years (this is version 4) and is now a 6 element Yagi Uda (poor Uda never seems to get a mention), based on a DK7ZB design, with a little tweaking in EZNEC.
    The challenge for this antenna was that it had to be compact enough to walk up a mountain and be very quick and easy to assemble and disassemble. 6 elements was chosen, as the boom length is 2m (6.5ft) which keeps it portable, whilst still having good gain. The next problem was how to build it so it can be put together quickly. After a lot of thinking, I decided to use wooden clothes pegs to mount the elements and driven element. Previous versions I have made used large screw terminal blocks, perspex, plastic booms, but this is certainly the best version so far!
    Note: The version I built, as described on this page, is optimised for SSB at the low end of the 2m band (144.3MHz) and will not be suitable for using at or above 146MHz. Bill, VE7WNO built this Yagi and observed the SWR shot up above 146MHz (see SWR plot above 146MHz here), so I have designed a version of this antenna centered on 146MHz for more broadband coverage of the USA/Canadian allocation of 144-148MHz. The dimensions for the all band coverage version can be seen here and SWR plot is here. It also uses �” tubing (6.35mm) instead of 6mm. See Bills comments at the bottom of the page for more info. OK, on with the 144MHz build…The dimensions are below:
    The dimensions of the 2m beam antenna, centered on 144.4MHz. Click for a larger image.


  4. #4

    Horizontal radiation pattern


    Vertical radiation pattern




  5. #5
    Elevation plot with the antenna at 5 metres above ground, for example in a portable set-up. Peak gain 17.1dBi at 6
    ‘3D’ view of radiation pattern

    SWR plotted from 143MHz to 146MHz with cursor at 144.4MHz.





  6. #6
    First test with antenna mounted 3m above ground. Very happy to see this on the analyser! Never seen it like this before on any other antenna.

    Of course there are many ways to fabricate a Yagi antenna, but hopefully this page gives you some idea of some options. Below are some photos showing in detail how the antenna is put together.
    The antenna disassembled. It can be put together in 30 seconds!


    The assembled Yagi.


  7. #7

    The elements are numbered and marked with a black centre line for ease of assembly.


    An element in place. The black line is centred to the screw, which is centred to the boom.


    The driven element has a larger plate to accommodate the box which contains the choke and driver assembly.


    I have used an unknown ferrite with 4 turns of RG174 as a common mode choke. I first tried a small air wound choke, but it was not very effective. I have yet to test this method with 100w of RF power, but I think it will be OK.

  8. #8
    Gil, F4WBY built this antenna to use with his new Icom IC-251E and made a video of his build, which you can see below. Cheers Gil!


    Some photos of using my original homemade Yagi are below. I shall add some of the new one shortly!

  9. #9
    DIY Satellite Antenna
    DIY Satellite Antenna
    Notes:
    1. All measurements are in millimeters (mm).
    2. Use 3 mm copper or aluminum elements.
    3. Adjust the critical gaps for lowest SWR (adjust the 14 mm and 22 mm gaps as needed).
    4. Only the VHF elements (Moxon part) are connected to the feedline. The UHF element (325 mm) closest to the feedpoint is the UHF driven element. It is not connected to the feedline, but resonates only when the proper gap is achieved.
    5. The feedline connects directly to the radio (no diplexer/duplexer needed).
    6. Use translucent plastic insulator from an RG8 cable for the 14 mm Moxon gap
    7. Use non-metallic boom (wood or orange PVC pipe).
    8. The feedpoint gap is 10 mm.
    9. The antenna works with any dual-band UHF-VHF radios
    10. For inquiries, email me at du1au@nightskyinfocus.com
    Прикажи превод


















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