Radio Corner

General => CB & PMR446 => Topic started by: John on Jun 18, 2026, 06:24 PM

Title: Quadrifilar Helicoidal PMR
Post by: John on Jun 18, 2026, 06:24 PM
Hello Everyone

As I have many problems with making a standard 1/4 wave antenna to get Vswr below 2.2 . I thought sod it and go for something completely mad and try this . Most make it for 430 MHz Satellites etc. So with a tweak or two . This one is at the moment Vswr of 1.79. A little more golden screw driver maybe I will get lucky.
Any way here is a pic . Wish me luck .
IMG_3746.jpg
Best 73's Mr CT4515  on his little hill
Title: Re: Quadrifilar Helicoidal PMR
Post by: M9JVQ on Jun 18, 2026, 09:14 PM
That's a work of art John. 8)
I hope your golden screwdriver works for a lower SWR, :)
Title: Re: Quadrifilar Helicoidal PMR
Post by: Jonny5’s on Jun 18, 2026, 11:43 PM
That looks amazing, I need one! I know I'm not far but I could get you 59 on the handie stock antenna indoors, when I spoke to you I was in the garden though. Is the completely home brew, looks mad, also looks very well made!
Title: Re: Quadrifilar Helicoidal PMR
Post by: Jonny5’s on Jun 18, 2026, 11:44 PM
Ah, the base is a 3d print, right? Very good!
Title: Re: Quadrifilar Helicoidal PMR
Post by: John on Jun 19, 2026, 10:59 AM
Quote from: M9JVQ on Jun 18, 2026, 09:14 PMThat's a work of art John. 8)
I hope your golden screwdriver works for a lower SWR, :)
Cheers Tony I will give it a go  ;D  ;D  ;D
Title: Re: Quadrifilar Helicoidal PMR
Post by: John on Jun 19, 2026, 11:03 AM
Quote from: Jonny5's on Jun 18, 2026, 11:43 PMThat looks amazing, I need one! I know I'm not far but I could get you 59 on the handie stock antenna indoors, when I spoke to you I was in the garden though. Is the completely home brew, looks mad, also looks very well made!
Thank You Jonny 5 .
Yes the base is 3d printed . I could print one for you . Just get the other parts yourself and have a go. I will help in the build process if needed. I think even if I can't get Vswr down any more it just looks awesome . ;D  ;D
Title: Re: Quadrifilar Helicoidal PMR
Post by: Razz229 on Jun 20, 2026, 10:09 AM
That is a thing of beauty

and if it doesn't work, sharpen it up and fix it to a push mower 🤣🤣
Title: Re: Quadrifilar Helicoidal PMR
Post by: Jonny5’s on Jun 20, 2026, 06:19 PM
What's the length of this, do you know what the length would be for a 2m version?
Title: Re: Quadrifilar Helicoidal PMR
Post by: John on Jun 20, 2026, 09:43 PM
Hi Jonny

This one is about 210mm x 70mm .
A 2M one is about 695mm x 275mm .
Try the web site very helpful.
The Web site is as follows https://www.jcoppens.com/ant/qfh/calc.en.php

Cheers John
Title: Re: Quadrifilar Helicoidal PMR
Post by: Jonny5’s on Jun 22, 2026, 10:20 PM
I think I clicked on the link, tried understanding the calculator and dives in to that and forgot to give it a thumbs up and reply. Looks like an interesting antenna, haven't seen this before. Have you had any more luck with it, how do you recon it preforms compared to
Something like a Sputnik ground wave antenna?