MAAS DP-27 dipole antenna tuning

Hello all,

I just bought a Maas DP-27 dipole (Yes yes I know I could have made one etc etc but I had no materials and for the price of this and my time it was definitely easier and cheaper to buy this one). Anyway the quality of the dipole on first impressions is great, with stainless wire and connections and high quality plastic parts. Its a 1/2 wave at about 5m long












So I threw it up last night on my balcony (basically identical to the balcony in the pic from google images) I just left it resting on the timber face and swr'd it, the swr was sky high. I proceeded to shorten it and did get the swr to 1-1.5:1 but i had to shorten it a lot ! (I didn't cut it).



My question is, how much should I be shortening it at a time to make a difference ? It was pretty late and I wasn't giving it my absolute best, will be trying again tomorrow but would like some advice, Does it ideally need to be suspended and not lying on a surface ?

I would like to operate from 26.965 MHz - 27.855 MHz predominantly

Cheers & 73,

Mark

You need to tune it for where it's going to be used so that'll probably mean putting it up and down a fair few times and it's times like this where an antenna analyser becomes worth the money because you can take a reading then adjust it a bit and see how many kHz that amount of adjustment gives you. You can't do this with a SWR meter nearly as well.

Where you had it it'll have been capacitively coupling to loads of stuff, including the house wiring, so will appear electrically longer. You'll find when you move it to where it's going to be installed you're likely to need to lengthen the elements so it was a good job you didn't cut.

So I stuck the antenna back up today, (in an inverted V due to space) SWR was sky high and gradually shortened it and re tested and was still high until it just dropped off a cliff. Basically 1:1 at both ends of the band. Heard a small bit of chatter on 27.555 but I’m getting some really bad QRM. Not sure if this is because my power supply is about 1.5m away from the radio or just due to the fact that QRM is almost a guarantee in a relatively built up area.

Hi - welcome to the world of interference, which is sometimes not a nice place. If you’ve mounted the dipole on a hand rail as in the picture, I’d just try moving it. Pickup from nearby ADSL broadband cables and AC power cables would be my first thought. Re the power supply question - perhaps try bringing the antenna end close to the supply and see if it gets worse and worse. I have also tried a car battery to power the radio and turned the house power off to try to find the noisy thing, if that makes any sense. Happy hunting .

Thanks for the feedback Wilko88. My intention was never to have a permanent homebase as it so easy for me to drive 25 mins and be at ASL 4000ft which is why i'm predominantly static mobile but i did put this up to see if i could have some QSO from home but im not going to put massive effort into eliminating the noise. I will bring the dipole out with me mobile and string it up off a tree so all is not lost.

73's Mark