Mastodawn

I think the term ‘Flowerpot’ antenna came from the idea that you should be able to fit a 50MHz vertical dipole in a reasonably sized flowerpot and get on-air in a stealthy manner 😎🤓

Essentially it’s a piece of high quality RG-58 coax cut so there’s almost an equal length of inner conductor with the screen part removed, and a part with the screen still present. At the bottom, a coil made from that same cable on a 50mm circular plastic tubing/pipe terminates the antenna. Dead simple, and it works!

I built the 6m version a couple of years back and worked stations across Europe at #QRP levels, so this year I decided to try the 10m version, inspired by #VK1AD. Andrew built his to center at SSB, I decided to move mine slightly downwards in frequency because I’m mainly a CW-Kitty 🐱🙂

It turned out really well, at least if you ask my #nanovna ☺️

On-air tests will follow later this week 👌🏻👍🏼

#hamradio #hamr #cw #cwops #antennadesign #rfengineer #measurementmonday

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Giovanni - ZL2GX Jun 17, 2024

@oz1lqo There's some subtlety in the coil at the bottom - it has to be a really high impedance so the number of turns are designed so the distributed capacitance of the winding and the coil inductance form a parallel resonant circuit.

Quoting from VK2ZOI: "The choke needs to be resonant about 5 to 6% below the desired operating frequency. Closer spacing will sharpen (and deepen) the VSWR response; wider spacing flattens but raises the VSWR. curve."
from https://vk2zoi.com/articles/half-wave-flower-pot/

#amateurradio

Half-Wave Flower Pot Antenna – VK2ZOI

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Søren Kjærsgaard Jun 18, 2024

@gmoretti Thanks 😊 I know that article - I deliberately chose mine to be as sharp as possible because I’m CW-Only and I plan to use it /P (POTA, maybe SOTA in DK) with my IC-7000 (no ATU). Along with my 50MHz “Flowerpot”, it’s a really versatile setup 👍🏼

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Giovanni - ZL2GX Jun 18, 2024

@oz1lqo They are a nice compact and easy to construct antenna.

I saw an interesting variation in my archives: it was to have fewer turns on the coil and then cut through the insulation at each end of the coil and attach a variable capacitor across it. From memory this was from RadCom and enabled the parallel choking resonance to be tuned across multiple bands. Probably wouldn't work for your setup (no ATU) but seems a tip worth remembering.

#amateurradio #hamradio