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Dipole Antenna Center Insulator for SO239

Skraćena veza: https://pedja.supurovic.net/veza/9625

Building dipole antennas is always some kind of improvisation. Center insulator is quite simple and may be made in short time with jigsaw and drill.

As I jumped in CNC world I need some simple tasks to learn how to use FreeCAD and other software. So, dipole center piece is ideal just for that. I’ve finished project and learned a lot in the process.

Finished projects is uploaded to Thingverse: https://www.thingiverse.com/thing:4149187

You may use CNC mill or 3D printer to make this part. Pay attention to use material strong enough to survive possible strong forces.

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Dunax GPN-4B antenna construction details

Skraćena veza: https://pedja.supurovic.net/veza/8733

After few years of sitting on top of my apartment building I decided to bring my Dunax GPN-4B antenna down for repair as top capacitive hat was broken. I found out that there actually no technical details about fixing it. So I went through some work of gathering such information.

First I found out that manufacturer is out of business. Antenna is not in production any more and manufacturer site is down. I asked help from fellow hams, some sent me some info they had, some sent me contact info for manufacturer.I also used my own antenna to take measurements, so finally I got quite complete details that I believe could help other fellow hams trying to repair their own antennas but also ones that want to build similar antenna. […]
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Build grid dip meter adapter coil for antenna analyzer

Skraćena veza: https://pedja.supurovic.net/veza/8706

Antenna analyzer like MFJ-259, MFJ-225, MiniVNA and similar may be used as simple grid dip meter for measuring coils, traps and capacitors. All you need is grid dip meter adapter coil which you may buy (costs for MFJ adapter set is about 30 USD) or make it by yourself for few USD.

If you want to build on your own here are dimensions of original coils sold by MFJ.

Small coil for short wave frequencies: coil diameter 15mm, coil length 15mm, 30 turns of 0.5 mm copper wire wound on PVC tube. Coil inductance should be about 3.6μH. […]
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Portabl antena od ribolovačkog štapa

Skraćena veza: https://pedja.supurovic.net/veza/7644

portabl vertikalna antenaŠtap je od fiberglasa, dug je šest metara, a težak svega nekoliko stotina grama. Dovoljno je čvrst da se na njega može okačiti vertikalna antena pa i dipol. Sklopljen štap je dug 110 centimetara tako da je prihvatljiv da se nosi na rancu.

Antena je klasičan monoband dipol za 14 MHz, samo je monitran tako da se vrući krak okači na vrh štapa i visi kao uspravna antena, a drugi krak se postavi pod uglom od 45 stepeni kao jedan radijal i antena praktično radi kao GP sa jednim radijalom. Antena je umerena i SWR je 1:1.

Zračenje je određeno smerom radijala, tako da se premeštanjem radijala oko antene može menjati i smer zračenja. […]
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