Delta loop antenna on higher HF bands

[VK1DA]

During the 10m/6m challenge I built and used a single element diamond quad for 10m. Fed at the lowest corner, with the sides guyed and the apex was at about 6.5m on a 7m HD pole. It heard well, I got good reports and made contacts in the ARRL 10m contest. But I didn’t have a standard antenna to compare it with. I did turn it around by 60 degrees, by walking the side guys around to new points, to try for more JA contacts once the US signals faded out, I think it was slightly directional.

I am so used to subtracting the 5% allowance for end effect that I cut the full wave loop too short and had to add the 5% back to the top of it to get it to resonate. Bandwidth was good, it worked well at 28.06 and 28.5, I didn’t try the 29 mhz section of the band.

Loops don’t have any open ends, so the wire length required for resonance is very close to 100% of the free space length.

[DL3TU]

If your target is DX, I would always go for the delta loop. I used it on summits for all bands from 20 metres to 10 metres. It works great with moderate effort in building and set up.
Rx is really quiet on the loop. Take off angle is low and with our design fairly independent of ground properties.
Here is a short manual for the 20 m version. If you need the dimensions for higher bands, just let me know:

Delta Loop for the 20m band

If you want to spend more effort, a VDA could be interesting:

HB0/DL3TU – 2./ 3. October 2015

It is more complicated to build and set up but performs excellent - again with the focus on DX. I didn’t publish a detailed description yet but dimensions are available for all bands if you’re interested.

73, Roman

[HB9BCB]

@DL3TU

If your target is DX, I would always go for the delta loop. I used it on summits for all bands from 20 metres to 10 metres. It works great with moderate effort in building and set up.
Rx is really quiet on the loop. Take off angle is low and with our design fairly independent of ground properties.
Here is a short manual for the 20 m version.

Really a landing on the point, congratulations to the designer Uwe@DL4AAE.

Although on 20 m the gain at an elevation of 20 degrees appears to be only about 0.5 dB better than the 18 m / 2 m agl multi-band loop from Mirko@S52CU, the difference in terms of “portability” is considerable .

BTW, Ken@K6HPX noted that, for portable use, the C-Pole antenna could be a very good compromise between a delta loop and a simple ground plane antenna.
Thanks Ken for the hint.

[VK3AFW]

Hi Andy,
An inverted Vee link dipole will give good low angle performance without the visitor tripping radials for a vertical or the big winder full of wire for a loop.

A 40 m dipole can be converted to a 20 m loop with the aid of a short shorting link and a couple of nylon guys. Not worth it IMO. Tried it and not impressed.

Back to the tuned doublet.

73
Ron
VK3AFW

[S52CU]

Hi all,
Yes, portability of V shape Delta loop antenna is a drawback, so it is suitable mostly for drive on summits. But once on the summit, it is very easy to deploy. It is directional on higher bands, and can easily be rotated, which is not the case with A shape delta loop.
Of course, my usual activator antennas are EF, doublet or vertical, hi.
73,
Mirko S52CU

[MM0FMF]

Thanks for the comments and suggestions.

The reason for wanting an antenna with some “oomph” for the higher HF bands is two fold. Firstly there is a strong possibility that a future challenge will include 10m amongst other things although the MT have not actually finally agreed what will be and when but we have taken on board comments from those who commented. The second reason is the rather obvious fact that the Sun is waking up from her slumbers and early indications bode well for a more active maximum than last time.

Now the morbid bit… if you work on getting “three score years and ten” roaming the Earth and the Solar cycle averages 11years you get to see 6 maxima in your brief period here. Most people don’t start playing on HF till they are late teens etc. and that brings the number down to 4. The first 2 maxima when I was licenced I was less interested in HF and didn’t experience them and the last one was a serious blast at times. It also was a pretty rubbish maximum as well. So realistically I have 1 more maximum when I will hopefully be able to play SOTA on 10m etc. I very much hope there will be more than 1 but… See it’s being so cheerful that keeps me going! So I don’t want to waste the next maximum.

A delta loop and 1/4wave GP for 10m are my immediate designs to build. My 1/4wave GP for 12m weighs about 170g and adding an alternative radiating section or adding a link will only add 50g or so and gives me a twin band antenna that can stay in the bag now. I’m also considering seeing at how lightweight I can make a Christman phasing unit so I can drive 2x 1/4wave GP to give a steerable antenna. I’m not sure if the weight and trouble setting up 2 antennas will “weigh less” than a small PA instead and I want to compare this against a delta loop that is steerable by moving the guy ropes and letting it rotate about its mast.

Anyway things to make now and things to try when the lovely Nicola lets us out of lockdown.

Once more, thanks for the comments.

[M1EYP]

For the previous 12/10/6 flavour, I made a new GP. I cut the radials to be quarterwave on 12 and the driven element to be roughly halfway between quarterwave on 12 and on 10. Sounds a very sloppy approach, but I remembered from years ago that the VSWR was reasonable and usable for 12m on the 10m GP and vice versa. It worked well, and DX contacts were made on both bands!

[DL6GCA]

A long time ago I had a Delta-loop for 20m, which I had installed on the pole with fiberglass tubes. I had fed it with a smartuner sg-230. With it I could work all bands from 10 - 40m.
It was rotatable and inside the triangle were the yagis for 2m and 70cm.
I remember that it was a quite calm antenna. It worked quite well until a storm disinstalled it.

Last summer, inspired by Ignacio, I built a Delta-loop with plastic pipes for the electrical installation. The idea was, to get the possibility to change the direction. It was a fragile wind-prone thing and I discarded it.

I prefer quick and dirty at SOTA and I am quite happy with my vertical. I don’t see any advantage here compared to the effort.

73 Armin

[HB9BCB]

@M1EYP

For the previous 12/10/6 flavour, I made a new GP. I cut the radials to be quarterwave on 12 and the driven element to be roughly halfway between quarterwave on 12 and on 10. Sounds a very sloppy approach, …

Yes, if raised high enough this can be a handy and satisfactory solution for dx.
I also experimented with a similar version years ago for 15-12-10m (dimension and vertical radiation diagrams below). Initially, the intention was to trim the antenna to 12m for resonance, but the highly praised fiberglass masts required a shortening of the vertical radiator lengths by approx. 12% …
Therefore a variant was implemented that could be matched by a simple ATU on all 3 bands. The ATU at the feed point (or with a 1m of RG58) was a L-network (series L), switchable between Hi-Z (12 and 10m) and Lo-Z (15m).
Ambitious operators who like to work in S&P could alternatively attach a remote ATU on the mast.

For comparison, the 15-12-10m vertical radiation diagrams of a 6 and 9m long vertical antenna with 2 radials of 4.20m each (below):
The 6m Vertical looks not bad, while the 9m Vertical looks not very exhilarating, both are no longer easy to match. But how do you say "When a band is open, almost any piece of wire is sufficient also for dx …).

[K1JNT]

Maybe also take a look at rectangular loops if you can handle monoband usage. 2:1 proportioned upright loops have 50 ohm feedpoint, so no need for tuner. Been using ones for 6,10, and 15 meter bands here at home. Needs some support out at the corners to keep them fairly square, but there’s no reason why 6 and 10 couldn’t be portable…and maybe 15m too. Hard to make a complete assessment, but I’d always go for a loop versus a dipole. Hopefully know more about a 10m comparison when the ARRL 10m contest happens in a couple weeks. I’ll have both a vertical and the loop working…and looking forward to it.

[VK1DA]

As these antennas (loops) have only minor gain unless they have a reflector or director added, a simpler way to get a few db of gain is a DEZ. For 20m the DEZ is about 88 ft long, ie. it is two 5/8 wave elements fed as a doublet. The feed impedance is reactive, with judicious choice of feedline length the reactance can be compensated.

The simplest way of doing all that is the ZS6BKW which is slightly longer than a DEZ but still does have a few db of gain on 20m. Better if it is horizontal and high, like all antennas.

73 Andrew VK1DA/VK2UH

[M1EYP]

Talking of which, I haven’t done a “test and train” activation ahead of the 12m-10m-6m SOTA Challenge flavour yet - and it starts on Tuesday!

So I’ll take the “somewhere between 10m and 12m” groundplane up Cloud this morning and give it a whirl. CQWW CW on 10m and SOTA chasers on 12m. Probably.

[HB9EAJ]

Albeit not exactly a delta loop and neither for HF but for the 6 meter band, following my experiences.

I was missing a 6m antenna and therefore was looking for a simple to build antenna to experiment with during the 6/10/12m challenge. I found a very simple to build delta loop that shows about 50 Ohms at the feed point, by changing the aspect ratios (description in German: Delta-Loop für 6m mit einfachsten Mitteln › HAMSPIRIT.DE).

Then I thought it would be even better (in terms of performance) to build a quad, or for easier construction a diamond shaped quad. DK7ZB has an interesting idea (scroll down to the Rhombic Loop): The DK7ZB Oblong.

Yesterday it looked like I should be able to activate a summit WX-wise in the nearby black forrest, so I hurried in building the loop in the morning. Fortunately, all material was by hand, so I needed less than half an hour to build it.

The first thing after arriving on DM/BW-293 was tuning the loop for resonance and after two cut-offs, my fingers were freezing and it was good enough for a quick try.

Unfortunately, no one was answering my SSB calls on 50.285 MHz, so I have no idea if it really performs. I also gave up after some minutes calling, since no mobile network was available, so I had to use APRS to send a spot that needed further precious time in the cold.

I will definitely try it another time, by tuning the loop more exactly, in warmer weather and easier spotting possibilities.

Even I could only make one local (65km) 10m contact (out of a total of 24) by using my compact EFHW antenna (better on 10m than my standard EFHW and shown at SOTLAS), the activation was great fun with the first snow in this winter season and I definitely have learnt new things!

Update and note to other 6m/50MHz activators in DL:
A kind German ham informed me today that in Germany one can only use the 6 meter band from a fixed station, but not with a portable station, at least until the end of this year.
Official reference: https://www.bundesnetzagentur.de/SharedDocs/Downloads/DE/Sachgebiete/Telekommunikation/Unternehmen_Institutionen/Frequenzen/Amateurfunk/AmtsblattverfuegungenAFu/Mitt1112020.pdf?__blob=publicationFile&v=11

I was aware that only horizontal polarization is allowed in Germany. This was another reason, why I built this diamond quad, fed from below. I informed myself before building the antenna by checking the German band plan from the DARC (German Amateur Radio Club, see https://www.darc.de/fileadmin/filemounts/referate/vus/bandplaene/VHF_Bandplan_6_m_Mai_2020.pdf), but the above mentioned restriction is missing in this leaflet.

I assume in the following days there will be an update in this matter, since the current rules are only valid until 31.12.2020.

73 Stephan

[GM4JXP]

Hi Roman, I would be interested to get the dimensions for other bands. I have used your 20m design on my last 3 activations and been very pleased with it. I sent you an email as well to the address on your QRZ page,

Thanks, Simon

[DL3TU]

Hi Simon,

thanks for your feedback! The email didn’t arrive, but I can post the dimensions here anyway.

I would be interested in your experience with the delta loop on 20m. Do you have any photos? Did you work DX? I never used the loop for a normal activation because it is more effort to set up than e.g. a random wire. I used it for the VK/ZL S2S events and in HB0, though.

Please find the dimensions for different bands in the following chart:

You can find the circumference in the last column (U2/m). It was calculated for a bare wire. When using an insulated wire, the length will be somewhat shorter.

Good luck!
73, Roman

[GM4JXP]

Hi Roman,

Thanks for the quick reply. I tuned my 20m loop centered on 14.2 MHz and used a cheap insulated wire from Sotabeams, but otherwise used the dimensions in your table. Feedpoint measured 50ohm and SWR was excellent over a wide bandwidth. I support it on a shortened DX Commander fibreglass mast and it normally takes me about 20 minutes to set up, depending on the terrain. Best DX so far includes NW7E Oregon, KR7Q Montana, WB6POT Calif. Furthest East is OD5ZZ. Dennis W0JX in Ohio gave me a comparison report with my Hyendfed, the loop being 2-3 S points better - the difference was so marked that he called me again after I had finished our initial QSO using the Hyendfed, after which I had switched to the loop. He wanted to know what I’d done… Comparison reports with EU stations showed little difference between the two. Note that I work QRO with 50w.
Photo from my last activation: In your experience, does it make much difference in performance if the base section is horizontal, drooping or as in the photo, angled downwards?

73 Simon

[MM0FMF]

I can’t make out which wires are which Simon… can you draw over the delta loop wires in that picture to highlight them?

[GM4JXP]

Here you go Andy:

[GM4JXP]

and this was my first activation with the loop, using a Spiderbeam mast. I’ve switched to the DX Commander now as its much lighter. Note the bottom part of the loop is drooping, hence my question to Roman. I think the wires are clear enough in this one.

[DL3TU]

Thanks for the photos and the report, Simon! I’m glad to hear that it was ‘plug and play’ and you were able to work DX with the delta loop.
Quite impressive that W0JX reported the delta loop being 2…3 S-units above the Hyendfed. The theoretical gain is about 3.5dBi but I believe the low take off angle makes the difference.
It also sounds reasonable that you received similar reports for both antennas across Europe. The low take off angle is of little help here.

@GM4JXP

In your experience, does it make much difference in performance if the base section is horizontal, drooping or as in the photo, angled downwards?

We know that variations in the height of the base section will change the resonant frequency and sometimes the impedance. But we never did experiments how the performance will change.
I recommend making the base section as straight and horizontal as possible. Two poles of 2 m length, one for each corner, would be ideal but I think that’s out of scope. In most cases it can be accomplished with a string of about 10 m length in each corner.

73, Roman