FYM-Delta-loop antenna by PA3FYM

FYM-delta-loopRemco PA3FYM is a big inspiration of many of my projects. This time he convinced me to build the famous FYM-delta-loop as a holiday antenna. Actually it’s a quite simple design from 2015 of the well known delta-loop. In Remco’s design of the FYM-delta-loop it is tuned for 40 meters. Not accidental because during the summer every night there is organized a ‘holiday’ qso-party (vakantieronde) on 40 meter where all local hams (on holiday or just at home) will participate and tell each other how nice their holiday weather and how cold their beer is. So being heard on 40 meters in Europe is an important design feature for the FYM-delta-loop. Being on holiday and profit of the (hopefully) low QRM-levels also gives the need for a good DX-capable antenna. So Remco changed the design of a standard delta-loop so it can do both: low and high radiation angle.

Base of the antenna

The base of the FYM-delta-loop is a 12,5 meter glass fiber mast like my Spider Beam Pole. Actually in Remco’s design the top height should not be less then 13 meters. I have to find a fence or small pole on my holiday destination to put up the Spider Beam mast. From there it is pretty straight forward. Take 43 meters of wire and shape it in a delta-loop. The lowest part of the FYM-delta-loop should be around 50 cm above ground. Actually that is the big secret of Remco’s design. Because the delta-loop is put up so low to the ground in combination with location of the feed point, you will get a pretty clean 50 Ohm impedance and a radiation pattern that holds between DX and local. Quite ideal for 40 meters.

43 meters of wire

For a starter: 43 meters of wire is too long. But it’s a safe start. You will end up cutting some of the wire to find the right resonance. Every part of the triangle is about 14 meters. When I did put up my Spider Beam pole in the middle of my 14 meters deep yard it was bit of a challenge to spread out all the wire. But opening my fence door gave me that extra needed meter.

Feed point of the FYM-delta-loop

unun 1:4 by PA0FRI
The FYM-delta-loop is an unbalanced antenna. It will be fed from 50 ohm coax which is also unbalanced. The so called ‘balun’ will actually be an unun. Since the FYM-delta-loop’s feeding point is in the corner (this in combination with the exact height will give the antenna it’s remarkable radiation pattern), the impedance will be 200 ohm. We need to transform from 200 ohm to 50. A 1:4-unun will do. I used a 4C65 core to wind the unun. 10 or 11 winding’s should be enough.

First time on the air

First thing that immediately is noticeable is the serenity sound of the loop. Even in my filled with QRM backyard in the middle of a residential area the loop picks up so little static and QRM in comparison with my ZS6BKW. For a few minutes I just sat there enjoying the view of a clean IC-7300 waterfall filled with signals. I realized I was testing the FYM-delta-loop, I had produce some signals. Since my new call Reversed Beacon Network doesn’t pickup my signals as good as before anymore (bummer), I had to give a CQ with my old call to get a good report. It probably has something to do with the ‘e’ in the suffix. It was in the afternoon, on 40 meters I didn’t count on many DX-reports. And indeed, it didn’t. But what was noticeable I got reports from every corner of Europe! Normally to get this much reports on 40 meter I have to use a big amplifier.

Other bands

The FYM-delta-loop is resonant on 40 meters with a width of around 200kHz. It covers the whole band. But that’s not the only band! It also works on 20, 15 and 10 meters without any matching. The radiation pattern is less optimal then 40 but it is possible to do other bands when you are on holiday. I even got it tuned on 30, 17 and 12 meters with the internal tuner of the IC-7300. I am anxious to set it up in a free and open environment on my holiday destination. This antenna could be a winner for sure. More reports will follow.

Remco’s own details on the FYM-delta-loop (dutch)

4 Replies to “FYM-Delta-loop antenna by PA3FYM”

  1. Cool stuff have there! We could organize a field day during our radio-weekend in the end of May to put this antenna to the test. I am looking forward to it already.

  2. Great blog post Jim,

    Very interesting results. I would expect a closed loop system to reduce received noice a lot. Is it single band only?

    1. Hi Mark! Thanks for you comment. It is resonant on 40m but it also has a dip on 20m and 10m. On 15m the SWR is acceptable (tuneable). It has a less optimal radiation pattern on other bands then 40m.

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