Modifying my 40m delta loop to work on other bands

Back in June 2011 I put up a horizontal delta loop for 40m and I wrote about it at some length here.  Since then, I’ve made a few changes to my aerial for the lower bands, experimented with an off-centre fed dipole, a resonant dipole for 40m and a doublet fed through my SGC smartuner before ending up back with a delta loop. Initially I used a 4:1 current balun which allowed it to work on 80m as well as 40m but but in the second version, I fed it with a quarter wave (adjusted for velocity factor) of 75 ohm coax as a matching section to make it a true single band aerial.  Of course, being a horizontal loop at less than 20ft AGL, it was always a cloudwarmer but very good for inter-G and western Europe – I never had to call more than twice to break any pileup I tried to work, normally making it first time.

I’ve been frustrated for some time that I’ve not had aerials for 160m, 80m, 60m and 30m so yesterday after the BARTG RTTY sprint contest I lowered the delta loop and extended it with another 8m or so of wire.  I then disconnected the length of 75 ohm coax and connected the loop directly to my SG-237 smartuner.

It only took a couple of minutes for me to determine that the tuner was happy with the length and so I can now use it for 160m, 80m, 60m, 40m and 30m.  It will be a compromise on 40m compared to the previous configuration but I can live with the inconvenience of that as it allows the other bands to be used.

Now we all know that just because a tuner can make a random piece of wire appear to resonate, that doesn’t mean it actually radiates very well so to test this, I had a quick half an hour tune from the bottom of 160m during the CQ160 CW contest yesterday evening working a few stations.  I worked into OH0, ON, E7, 9A, ES, UA, DL, GM, OH, OM, HA, YL, LY, PA, S5, SP and UR so it clearly does work.  That’s taken my all time DXCC count on top band from a mere three up to twenty!

I also ran a quick WSPR session on 30m running just five watts where I was heard throughout Europe and over to the east coast of America.

This was a good result for just an hours work yesterday and I’m very pleased that I can now get some RF into the air on the lower bands.

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5 Responses to Modifying my 40m delta loop to work on other bands

  1. Bas PE4BAS says:

    Hello Keith, I received you yesterday on 30m WSPR with my 84m horizontal loop. I didn’t see me spotted by you unfortenately. 73, Bas

    • g6nhu says:

      Hi Bas, yes I noticed that yesterday and was a little disappointed that I didn’t receive your signal back. I wasn’t on for very long though.

  2. Steve M0MUF says:

    Hi Keith

    I read this post with interest back in January and having stuck up a 50m (ish) loop today, remembered it and thought I ought to have another look. I’m not getting such good results as you, it must be said. It could, perhaps, do with being a couple of metres shorter, but currently only seems to work on 60m, 40m, (I didn’t try 30) and 17m (ish). Whilst this isn’t bad, being able to use 160, 80 and 20m as well would be better. You mention your tuner is connected directly to the loop, could you expand a little – is it up in the air?

    • g6nhu says:

      Hi Steve,

      Yes – My tuner is up in the air, it’s mounted to the standoff which holds my mast in place and so I just ran the two ends from the loop straight to the tuner.

      As can be seen from my post, it worked. But I quickly found out that it didn’t work as well as I’d have hoped. At the time, I hadn’t checked the full specs of the tuner so wasn’t sure how much power I could run using CW so I limited myself to 20 watts and all was well. However, when I turned the power up for SSB or tried to run more power on CW, the tuner kept losing tune and going through another cycle. It turned out that by locating the tuner within the loop itself, I was getting a lot of RF feedback and causing the tuner to cycle.

      I tried a number of things to stop RF getting back in but none of them were successful so in the end I took the loop down and installed a random length doublet which goes from the top of my mast to a 20ft pole at the end of the garden with 450 ohm open feeder back to the tuner. It’s not as good as the loop on 40m but it works significantly better on 160m, 80m, 60m and 30m.

      73 Keith.

      • Steve says:

        Thanks Keith, useful to know. I might have a play and see what I can get it to do. I’ll let you know if I learn anything useful.

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