40M Loading Coil for AT-271 folding antenna.

by VA3TNE May 29, 2017
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Wonder if you could design some formers for 80m, currently have a 40 wire DP but would be nice to add 80m?

Local shop here sells the whip and bag for $40.

How did I miss this?

Looks like a good addition to my AT-271.



Does anyone know where i can get a similar one to this but twice the length?, I have used this one for a few of my ham projects but would like a longer one in order to make a vertical screwdriver antenna... Thanks to the designer of this one also, it works fantastically well.

I would be happy to create a variation. What length, diameter, and number of turns would you like? I will be happy to do one for you.

That would be fantastic thank you, pretty much exactly the same as this one only around 180mm long (high) I tried to take two of these and join them together but my knowledge and skill for this kind of thing is very very limited, so 40x180 with the winding's spaced the same as this one from the bottom to the top....



I've made long versions. One with the fly-wire grooves, and one without. Both of them have a plain center because I think you should epoxy a dowel down the interior for better support. I don't think it'll be strong enough with just printed parts in the center.

Fantastic matey thank you so much....... I usually reinforce them with another tube down the centre...... i only wish I could do this stuff, you guys are so cool at what you do, I can build a dragbike that'll run 7 seconds, but when it comes to computers I leave that kind of stuff to those who know what they're doing.... Thanks again Adrian :) I will post up a picture and build thread when I have done it on the facebook page :)

For those unable to find the AT-271 folding whips, the Buddipole long telescopic whip available from http://www.buddipole.com/ is a direct substitute.
I suggest that you put lots of Crazy Glue (the watery version) all over the center piece (including the ends) before installing it in the coil. When the glue has soaked in and cured, it will strengthen the center piece and help prevent stress breaks. Also I used a flat washer inside one of the end caps to fill the space so there is no gap. You can glue the end caps on when finished. I also used a flat washer on the outside at both ends rather than try to force the nut into the shaped depression on the end caps.

Thank you for the loading coil design. Printed perfectly at 0.3mm layers on my TEVO Little Monster. No problems with the coil forms or over hangs. I printed it at 100mm in the Z dimension to give me a little more inductance which I will use with a shorting clip as you mention above.

Cheers for the great design. I look forward to seeing more of them.


Thanks for the kind words.

I too have had success at .2mm layer thickness. I lowered my extruder temp and it printed much nicer.

I've been looking for additional things to design, and have come up with a few. Most have been posted, others I'm still working on.

If you have any suggestions, I'm always looking for something to practice my CAD skills on.

I'd like to see a feed point designed for this loading coil similar to the Chameloen antenna. Then by adding the MFJ1979 stainless steel whip you have a nice portable HF antenna. I am now using the loading coil with a wire antenna on holiday in Italy. I clear coated the whole thing once it was wound. Now that I have build it. I can say that the design is excellent and the thought that you put into the internal parts was a real time safer that also makes this a solid robust unit. I used 10mm stainless steel studs on my unit. Love it.

Neil I/PA3OMG at the moment.