Portable Operations

Martin Vk3TMP

Testing the setup on the Thursday Coffee meet.

Lino, VK3EI, entertained the Thursday group with his latest creation he brought along to test out. Lino has printed, yes printed, a very nicely constructed remotely operated vertical antenna for 40m and up that gained the attention of the group.

The unit consists of a sectional mast (12m Spiderbeam) with an outrigger pulley to around 9m. About 1m above ground is Lino’s ‘engine’ project comprising a tape-measure, a 12vdc hobby motor mount and a Dacron braided line spool with a friction clutch – all running to Lino’s mobile ‘shack’ – a Mercedes Viano.

The tape measure is bare of paint on the front side to provide a good contact with a strip of beryllium copper kept under tension by a spring and being fed by coax through a line isolating current balun that keeps any current mode RF from flowing on the coax braid. A switched coil is also mounted to allow operation on 40m and 80m.  This 30microhenry loading coil is tapped at approximately 5 microhenry; the small portion of the coil is always in circuit and allows the 8m section of tape to resonate on 40m. When the full coil is switched into circuit the  tape section is made to resonate on 80m. 

The motor drive uses a toothed belt with approximately 4:1 ratio to drive a spool of Dacron rope which is used to adjust the length of the tape measure. As a safety option, Lino has developed a tidy little spring-loaded friction clutch between the spool and drive. The clutch utilises three spring loaded arms (on a rotor) with a moving pressure cap on each arm that runs around the printed drum.

Whilst still evolving, the prototype is showing promise as an effective way of managing a multi-band vertical that can be quickly adjusted to any frequency from the operator position. The control box consists of a switch that allows the tape to be moved up and down and an integral speed control circuit allows the motor speed to be adjusted for fine tuning, if needed.

Technical details:

3D Printer –  VK3EI designed and built.

Plastic consumables –  all parts printed using either PLA+ or PETG plastic filament.

Printer control –  Printing software used is Simplify3D.

CAD software –  All parts are drawn using AutoDesk Fusion 360.

Design library source – No external libraries required.

Challenges – The clutch design was the  most fiddly part of the whole build.

Print time – Approx 40 hours.

FB link –

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How about your story? I’m happy to help and only need a bit of information and a couple of jpg photos.         Regards, Martin VK3TMP.