Portable 70cm 1/4 wave

Due to my terrible home QTH for radio I tend to go out mobile and with a decent dry summer I’ve been walking on the hills around Holmfirth with my trusty Anytone.

Although the standard rubber duck does a surprising job I wanted a bit more so after lashing together a quick 1/4 wave I was surprised by it’s performance so I decided to refine the antenna for pack size and weight.

I managed to find a BNC connector with a M10x1.0 thread, that may sound a bit unusual but there’s a reason why I chose such a thread, because it’s used as a automotive brake pipe fitting size and as I work in the motor trade I have a ready supply of such things. Again after making sure that worked I decided to refine further and ask a local engineer to turn up the fitting in the pics to make a better job of holding the radials.

The radiating element is simple copper wire and is sleeved with polyamide tube, 2mm ID, 6mm OD, just what you’d find on vehicles from the 70’s and 80’s using Bosch K-Jet (Porsche CIS) injection systems and finished off with a black PVC cap. The Polyamide tube is sealed to the radial holder by means of a simple wiring grommet.
The radials are again things I had at work namely some 3mm or so aluminium TIG welding rods which have been tapped to M3 and since I took the pics have been again capped with some black PVC caps to stop me poking my eyes out!

The antenna has changed a little since the pics were taken as it has been tuned for the 70cm band and therefore is a lot shorter than the pictures! the mounting tab has also been finessed and looks a lot less agricultural!
I’ve managed to get the bandwidth wide enough to cover both the 70cm band and as far up as PMR446 with the best SWR of 1.00:1 at best at 49Ω and at worst 1.15:1 which I’m happy with.

The antenna is used in conjunction with a mast I have made from re-purposed tent poles that lash to a UK “Trig Point” and gives around an antenna height of around 4M above ground level, but, can also be mounted on ground by using a 3 tent pegs.
The whole kit and caboodle, mast, antenna and 5M of Hyperflex 5 weighs in at 950g and packs down small enough to carry in a ruck sack and if I’ve done my sums right should only exhibit 1dB of loss.

All in all I’m really pleased with how it all turned out, it performs well and have had 70 mile contacts on 5 watts in normal conditions from one of my hill top perches.