Tag Archives: Field Radio

Radio Field Craft: Rand explores the handy Prusik Knot

Many thanks to Rand (W7UDT) who shares the following guest post:


The Prusik Knot… strain relief for Wire Antennas and Coax.

By W7UDT, Randall ‘Rand’ Tom

The Prusik knot is a simple, yet effective means to provide needed strain relief to wire antennas and coax, while deployed. It’s comprised of a simple loop or length of suitable cordage (of smaller diameter than the shank, Coax or Wire, it secures).

The link below, is from our friends at Animated Knots…. It’s a brief video tutorial on how best to tie the Prusik knot. Having the Prusik in your ‘bag of tricks,’ will help make your next field deployment be a successful one.

https://www.animatedknots.com/Prusik-knot

As seen in the instructional video, the knot is comprised of a simple loop of cordage, sufficient in length for the task, which is fine, but, I would recommend NOT making a loop. Rather, keeping tag ends for easier anchoring. These tag ends should be at least 12” in length. This is called an open-ended Prusik. Either way, both have utility.

To do this, fold a 24” of cordage in half, to make a ‘bite.’ Lay the bite over the shank of the coax or wire, and feed the tag ends inside the bite loop. This forms a larks-head knot. Wrap two additional turns around and through, then dress and test the knot to form the Prusik. Simple. Anchor (tie) the tag ends at a point where strain relief is best positioned. Then adjust (slide) it to load.

After deployment, I would also recommend leaving the Prusik attached. It comes in handy, when coiling your feed lines or elements later for proper storage.

The Prusik allows it to slide along the wire or coax while free of tension, yet it holds fast under load. Much like a monkey’s fist hanging onto a vine. The tag ends, can then be affixed to suitable anchor where needed. The key here, is using a smaller diameter cordage, than the wire or coax itself.

The Prusik, along with similar ‘Friction Hitches’, can be used in any number of applications in Ham Radio. e.g. Anchoring coax, joining linked antenna elements, power cords, and adjustable guying. The list is long, wherever strain relief is needed.

I would encourage you to tie it, try it, test it, and judge for yourselves. As well, I would encourage you to check out other useful climbing friction hitches… YouTube is a great place to start. I hope you find this useful afield, and to hear you ‘On the Air!’

73! de W7UDT (dit dit)

W7UDT, ‘Rand’, lives and operates near Boise Idaho, with his lovely wife Stacy. Portable QRP operations, along with his Jeep and Harley are his ‘vices.’ Your comments and questions are welcomed. My email is [email protected].

Treetop Antennas: Featured with my friend Wlodek (US7IGN) on BBC Radio 4 Short Cuts

I’m very honored to be featured with my good friend Wlodek (US7IGN) in a short radio documentary on BBC Radio 4 today.

Wlodek is long-time reader and subscriber here on QRPer.com and the SWLing Post. Wlodek lives in Kiev, Ukraine and we keep in touch these days over email. Like me, he is passionate about field radio work and before the Russian invasion, you’d often find him in nearby forests experimenting with some pretty impressive field antennas.

Sadly, when Russia invaded Ukraine earlier this year, it very quickly brought an end to all of that for Wlod. Not only were amateur radio operators not allowed to transmit under the state of emergency, but it’s no longer safe to venture into nearby forests.

Radio producer, Cicely Fell, learned about our love of all things field radio and put together an audio piece that airs today on BBC Radio 4:

BBC Radio 4 Short Cuts

From the forests of North Carolina, USA to the city of Kyiv, Ukraine – two ham radio enthusiasts seek each other out and a voice from the past prompts a dialogue on listening between a rabbi and a radio producer.

Click here to listen via the BBC Radio 4 website (note that the audio can be streamed shortly after the program airs today).

Many thanks to Cicely and her talented team at Falling Tree Productions for spending a little time with us in the forest and on the air! Truly an honor.