Nemecký rádioamatér Andreas DL6YCL is known for its practical solutions for antenna systems for microwave bands, especially in connection with operation via a geostationary transponder QO-100 (Es’hail-2). Medzi jeho projekty patrí aj moderný 3D tlačený YATT Helix ožarovač pre pásmo 2,4 GHz, ktorý predstavuje ľahko realizovateľné a výkonné riešenie pre satelitnú uplink anténu. Skratka YATT v názve znamená Yet Another Two Turn, čo odkazuje na kompaktný, ale účinný dizajn.
You will read in the article
Concept and determination
Ožarovač YATT Helix bol navrhnutý ako ožarovač (feed) pre parabolické reflektory, ktoré sa používajú v amatérskej satelitnej prevádzke. Je optimalizovaný pre uplink na frekvencii 2400 MHz, ktorá zodpovedá vysielacej časti transpondéra QO-100. Konštrukcia využíva dvojzávitovú helixovú anténu with circular polarization, located in front of the reflector, which ensures effective irradiation of the parabola with high efficiency and minimal gain attenuation.
Unlike some more complex irradiators, the YATT Helix is designed to be ľahko vyrobiteľný aj domácimi prostriedkami. Väčšina dielov sa dá vytlačiť na 3D tlačiarni a kovové prvky sa dopĺňajú bežnými komponentmi – ako sú mosadzné skrutky, koaxiálny konektor typu SMA a medený vodič pre helix.
Mechanical construction according to DL6YCL
The design of the irradiator consists of several basic parts:
- Reflektorová doska – a metal circular reflector with a diameter of approximately 70 mm, which ensures directionality and suppresses back radiation.
- 3D tlačené telo – a plastic holder that serves as a supporting structure of the helix and at the same time as a cover for the coaxial connection. In the DL6YCL model, it is designed for easy mounting on the LNB (converter) holder so that the radiator can be placed with the receiving LNB in the common focus of the dish.
- Helixový žiarič – a double-stranded copper spiral with a diameter of approximately 40 mm, made of a solid copper wire with a diameter of 1.5-2 mm. The size and pitch direction of the winding is designed so that the antenna works with right-handed circular polarization (RHCP), compatible with the QO-100 transponder.
- Prispôsobovacia (matching) platnička – a small triangular piece of sheet metal located near the feed point, which provides impedance matching to 50 Ω and improves the power transfer between the coax and the helix.
- Koaxiálne napájanie – SMA or N-type coaxial connector, attached from the back of the reflector. The middle wire of the connector is connected directly to the beginning of the helix, the shielding wire is connected to the reflector.
Andreas DL6YCL navrhol jednotlivé časti tak, aby bolo možné celý ožarovač vytlačiť bez potreby podpornej štruktúry and even a less experienced constructor managed the assembly. STL files for 3D printing are available on Thingiverse, as well as assembly instructions and dimensions for connecting to the coax connector.
Electrical parameters and adaptation
The YATT Helix irradiator has been optimized for the operating frequency 2400 MHz, pričom charakteristická impedancia je prispôsobená na 50 Ω. V experimentoch autora dosahovala anténa SWR pod 1,2 : 1, čo svedčí o veľmi dobrom prispôsobení bez potreby dodatočných ladení.
Simulácie a merania ukazujú, že ožarovač poskytuje zisk približne 11 dBi and the width of the main beam around 65°. These parameters are suitable for use with parabolickým reflektorom o priemere 60 – 100 cm, pričom v kombinácii s vhodným LNB poskytuje ideálnu geometriu pre súčasný príjem a vysielanie cez QO-100.
Materials and production
DL6YCL recommends printing the radiator body from UV stabilného PETG alebo ASA filamentu, ktoré lepšie odolávajú poveternostným vplyvom. Pre použitie v exteriéri, najmä v zimnom období, je dôležité, aby materiál mal nízku nasiakavosť a vysokú rozmerovú stabilitu.
Helix je najvhodnejšie vyrobiť z medeného drôtu (e.g. from solid electrical conductor CY 1.5 mm²). After winding on the template, it is important to maintain the exact distance between the turns, which determines the resonance and circular polarization. The reflector can be made of an aluminum sheet with a thickness of 1 mm or a copper disk.
Mechanical integration with LNB
Jedným z praktických aspektov návrhu DL6YCL je possibility of direct attachment of the irradiator to the LNB holder, čím sa dosiahne optimálne zladenie so spoločným ohniskom paraboly. Tento spôsob montáže minimalizuje straty a uľahčuje zarovnanie polarizácie.
The irradiator is mounted using a plastic adapter or sleeve that can be printed together with the body. The holder is designed for common LNBs with a diameter of 40 mm. In some cases, the radiator can be connected directly to the front cover of the LNB if a common bracket is used for a "dual-feed" configuration.
Operational experience
According to the experience of the author and several users published on portals Thingiverse a QRZ.com, YATT Helix ponúka stabilný výkon, minimálny SWR a spoľahlivú reprodukovateľnosť výsledkov. V kombinácii s výkonovým zosilňovačom 2,4 GHz s výkonom 2–5 W je možné dosiahnuť silný a čistý signál na uplinku QO-100 aj pri menších parabolách (60 cm).
Several radio amateurs have confirmed that the radiator has proven itself even in more demanding weather conditions - after more than a year of outdoor use, it did not show deterioration in parameters, especially if it was printed from high-quality ASA filament.
Advantages and practical notes
The main advantages of the YATT Helix irradiator include:
- simple and fast production without special tools,
- the possibility of 3D printing from commonly available materials,
- excellent matching to 50 Ω,
- suitable characteristic for parabolic reflectors up to 1 m,
- easy integration with LNB for QO-100,
- low weight and compact dimensions,
- high resistance to weather effects.
DL6YCL recommends checking the SWR before final assembly with VNA analyzátora, aby bolo možné doladiť vzdialenosť medzi helixom a reflektorom. Malé odchýlky môžu mať vplyv na impedančné prispôsobenie a polarizačnú čistotu.
Conclusion
Projekt YATT Helix by DL6YCL is an excellent example of a practical combination of modern technologies such as 3D tlač, s klasickou mikrovlnnou anténnou technikou. Vďaka jednoduchosti, dostupnosti a overenej funkčnosti sa stal obľúbeným riešením medzi rádioamatérmi, ktorí chcú vlastnoručne postaviť spoľahlivý a efektívny ožarovač pre QO-100.
Published 3D models and documentation available at Thingiverse allow anyone interested to make an irradiator exactly according to the original design. YATT Helix thus represents a modern, open and fully reproducible solution that combines the precision of the technical design with the creative approach of the radio amateur community.