Vertically polarized delta loop for 10m

A follow on and quick update on my loop I cobbled together that I started to hijack Lynton's Delta Loop thread with. I'll keep somewhat brief for now, some of you will be thankful to read, as am supposed to be packing for a trip.

If you didn't read the other thread, suggest you do, but in short it's a very simple 10m vertically polarized delta loop only a 1/4 wave high so great to fit in the lofts/attics of many houses. No balun or other matching device required as has a 50ish ohm feedpoint. Theoretically should have a good low angle of radiation and going by the results so far it would appear it does as well capturing single hop in to Europe.

My QTH conditions are that it is in my loft, so the lowest part of the antenna is about 1/2 wave length above ground (ground being the physical ground level outside my house). Should be fairly omnidirectional, but main lobes are firing north / south. My house is about 115m ASL. I have a clearish path through the hills of the UK in the direction of south America.

I've ran it for 15 days, from 1st through 15th July with 10W SSB and 10W FT8. Any SSB contacts using more than 10W are not included in the chart below, but that was only a couple. Most operations have been for just a little while in the evenings after work. A chunk of the SSB contacts were during the day last weekend.

With the data above, you can make your own assumptions to how well it is working from the below chart. It's too early for me to tell if it's overly directional, I'll keep playing with it for longer to see if propagation changes bringing the US and the middle East in to play. But for now, though the amount of daily QSOs can't match MW7TTA's, I think I'm happy with it which is the main thing

The dimensions are in the chart if anyone wants to copy it. For 11m add a couple of inches to the two longer legs.



Thanks Lynton for the inspiration. I am in love with this loop of wire

Fantastic stuff there Neal and thanks for posting your results as well as details of you Delta Loop.  

I was also inspired by Lynton's posting and had a bash at a loop in the loft for 6m. It worked very well but then I modified my ATU so that I could fire up the long doublet and found it operated with similar efficiency so down came the loop. (I wanted the coax for another project on the go. )


Have a good trip and thanks for all you do here at Charlie Tango.

Hi,
    I'm so glad you guys were inspired by my post and Neal those are some really fantastic results.
My loop is still performing quite well but in all honesty conditions haven't been great for me at the times I've been able to play radio.
I am amazed that something so simple performs so well. Like Neal I'm waiting for the US to start rolling in properly. I did hear some activity on the "Superbowl Ch6" a week or so ago but nothing since. I didn't bother putting out a call on that channel because I thought it'd be a waste of time given the amount of power those guys are shoving out and nothing was heard on any other channel.

Good DX

Lynton

Hi Lynton,

You'd be amazed how posting up and sharing what we do in the pursuit of our radio interests can inspire others to try things out for themselves also. I'm glad to have seen your original Delta loop posting and was able to try out my own version for 6m. It's down now after my never ending pursuit of making one wire do the job on many bands but was amazed how well it worked for a fairly straight forward antenna. It's definitely one antenna in-the-top-pocket collection of ideas and may surface again in my own pursuits.

Thanks again for your original posting, it gave at least a couple of us the incentive to try it out for ourselves and were suitably rewarded with good results.


All the best to you,
Victor

An update on the antenna.

I have run it as my main 10m antenna now since 1^st July. Whilst the initial chart I posted after a couple of weeks hinted that it may be directional, I can confirm that as the propagation has changed over the past 4 and a half months, it is not overly, and that it is generally just a good performing omni-directional vertical as the updated chart below shows. Same power settings as my original post as that is my choice to use and I also want to keep some continuity with the testing.



Now for a touch of lunacy. The antenna is a keeper and I will be using it for a good while longer, although it, along with the multiband fan-dipole and a few other contraptions in my loft make it a little difficult to fit in some other large wire arrangements.

What I thought I would do, mostly just for a laugh, was to use an external ATU to see if I could match the loop on other bands, and if it did match, could I actually make any contacts? Well in short, it did and I did.

I used MMANA to put my 10m dimensioned antenna through calculations on other bands. I won’t bore any of you with all the modelling, but have put a brief summary of what values it spat out for the bands. dbi gains (or losses) are at 5 degrees elevation. Note the ATU is at the transceiver end and the loop is fed with about 10m of RG213 coax, so there will be “some” loss there too. All HF contacts were FT4/8.
 
30m = SWR 4936, -8.4dbi.

If I was buying an antenna and it was advertised with those figures, it would not be my first choice, but it worked well. Contacts into Europe, north Africa, and USA.


80m = SWR 1848, -21.1dbi Vertical / Horizontal polarization of a 60 / 40 ratio, horizontal off the broadsides. High bubble pattern.

It would not match as a loop. I had to disconnect the shield of the coax to the ATU so it became more a long wire antenna, or rather a short wire one. No RF earth or counterpoise used. RF problems in the shack, to be expected I guess with no earthing. I had to disconnect the laptop charger and carefully match the antenna before plugging in the USB cable to run FT8 otherwise the laptop became part of the earthing and in short.. it did bad things. However, when all was matched I made contacts in UK and short way into mainland Europe.


160m = SWR 723, -29.3dbi!!! very similar pattern to 80m.

Do you want to know the ERP and probability of being able to make contacts with this one? I’ve done the maths, and paraphrasing K-2SO…



As 80m, 160m would not match as a loop so ran as a long (short) wire antenna again. And again, no RF earth or counterpoise. Oddly though, did not experience any kind of RF-in-the-shack problems at all on this band.

Miracles happened. I made contacts. Only in the UK and Europe, but that’s more than I would have had I not tried it. A DX antenna it is not, but I bet it could take on a ham stick mobile whip, and cost a darn site less.

I then tried out some higher bands...

6m = SWR 48, 1.7dbi mostly Vertical polarization, omni-directional + a high Horizontal lobe off the broadsides.

It works. I made contacts. Didn’t surprise me too much.
 
2m = SWR 6, 7.5dbi mostly Vertical polarization, omni-directional, but highest gain off vertical wire end. Many high lobes, some with higher gain than the 5 degrees one.

This made me laugh. The ATU (remember this is a ATU designed for HF) easily brought the SWR to a perfect match. I made respectable distance UK contacts (no tropo during testing times).


70cm = SWR 6, 12.6dbi (17.2dbi at 0 degrees). As at 2m, mostly Vertical polarization, omni-directional, but highest gain off vertical wire end. Many, many high and side lobes.



The HF ATU easily matched it again on this band and again I made contacts. That freakily awesome very low high gain lobe is pointing right at Alan MW7TTA, but alas I don’t think the UHF signal will ever get through those little hills in Wales that are between us.
 
So, there you have it. “Have what?” you might ask. I don’t really know actually. I guess if you ever ask questions of other “experienced” radio operators like “Can you use a HF ATU on UHF” or “Will a 10m piece of wire work as an antenna on 160m” and they just answer a straight “No.”, then just reply with “I find that answer vague and unconvincing**” and just go try it for yourself.

The loop is going back to mostly 10m use again now and will try with it here and there during the CT 11m Winter contest, but at least I know I can play other bands on it if I want. And, if you’ve read this far, you now know a setup that might work for you too.
 


**I may have possibly been watching Rogue One: A Star Wars Story while typing this up.

Hi Neal,

Really great to hear of your further experimentation with the antenna setup and ultimately what an ATU can do for you. (Would be nice to hear about your ATU you setup for it.)

Obviously your experiments have shown you what can be achieved and I hope inspires others to try out similar setups.


I'd tell you what I'd like for you to try out next, stick that ATU along with a current 1:1 Bal-Un on it's output to one of your longest dipoles and see how you fare with that. You might be pleasantly surprised.

(You'll get rid of the RF-back-in-the-shack issue for one. A FT-140-43 will suffice for low power, two stacked or a a FT240-43 for higher powers and maybe a 31 mix for 160m/80m operation. A short antenna may well saturate a toroid quickly or even the fun of 'flash-over' if your ATU is made up of lesser components.)

Oh, and always remember 'modelling' doesn't give you the complete story.


Nicely done Neal and look forward to hearing more.

All the best,
Victor

Hi Victor. Thank you. Hope you are doing ok by the way, as noticed you haven't been around a bit recently.

ATU is an Amtech 200. Not much about it on the net, but found adverts for it in scanned radio publications online dated '79 through '81. It's an extremely simple one, meant for long wire matching, even though the output has an SO239. 12 position switched inductor.. not a whole lot of winds around two cores, and a nice double gang air cap.. I can't tell you the value you, sorry, as my multi-meter doesn't have a capacitance setting. The cap was the reason I picked the unit up to make my own ATU, but the unit was so simple to fix it's staying as it is for now.



Got a 43 mix 1:1 on the output now (righthand side). Ignore the string of clip-on ferrites on the left, that's just my random antenna creation testing cable. A very brief play shows 6m and 30m matches good on the fan dipole, but 80m and 160m it's struggling with (longest dipole is for 40m). Might need to beef the ATU up a bit for the lower bands to work on the dipole.

Hiya Neal, been a bit out of it recently on medical grounds but back with a 'as good as it gets' scenario now. Won't let it spoil my enjoyment.

Nice simple little L-Match the old Amtech 200, with the 300 model just adding another variable capacitor to make it a Pi-Match. 

You could easily add a simple switch to this unit to flip the capacitor to either input or output side to match low & high antenna impedance. Another switch could be used to add capacitance in parallel to the variable capacitor and increase the matching range also. (You don't need Silver Mica types either, any good high voltage ceramic would do the job nicely.)

That'd probably help with regards matching your 40m dipole for 80m & maybe 160m as with it being too short the impedance will be very low. Your good match found on 6m & 30m is obviously due to that being a higher impedance on those frequencies.

All good fun for the playing, experimenting and of course learning.  

Your string of ferrites on the coax is similar to my additional setup and known as a W2DU or Maxwell choke. With the right amount and mix of ferrite material it does the 1:1 job nicely.

Great to hear about your experiments and best of all, sharing it with others.

73,
Victor

Hope things are ok for you Victor take it steady

Good to hear Victor, or at least I mean it's good to hear you are doing as good as you can now. Thank you for the info, will certainly look at adding in some more capacitance and / or fitting a switch to flip the cap between in and output.

Cheers Lionel, hope you are keeping well too.  



Thanks as well Neal, rattling like a Tic-Tac box here but still good to go.

Worth having a play with that ATU and don't go sweating it with all the mathematics or dreaded Smith charts either. A good handle on how the theory works along with some hands on soldering will stand in good stead. (A NanoVNA helps a lot with final calibrations but amazing how you hear the difference on receive to find your SWR is also low on transmit at that point.)


All the best to you both,
Victor

I am currently running my cage dipole along side this delta loop to compare them against each other. That is on the 10m and close by bands only, not random non-resonant frequencies like in my previous posts.

On receive, electrical birdies from neighbour's appliances aside, this loop has 2 to 3 S points on average lower background noise than the cage dipole. That is, using the FT-991A with the RF gain turned up full, but with no preamps turned on, the average background noise with the cage dipole is between 2 to 3 S points on the meter. Using the delta loop the S meter reads 0 background noise. The loop in almost every situation so far has helped weak stations to be more intelligible than when received on the cage.

Verdict still out on TX. A lot more playing to be done with them yet.

I have made a small mod to the loop which is a plastic spacer near the feed point which when slid a little towards the 1/4 vertical section, pulling the wires together to the left of the spaces (in the diagram), makes the centre point frequency higher. Alternatively, pushing the spacer towards the electrical choc block which stretches the wires out a bit, lowers the centre point frequency. Saves me chopping or adding bits of wire to use on the top end of 29 MHz or lower down the bands. As it stands on it's own without the spacer/tuner, the loop has nowhere near the bandwidth of the cage. At this moment that seems to be the cage's only bonus over the loop in that it can be used on such a wides frequency range.

Delta Loop was using my first proper contact from France 14PAT411 & 911 when i was with car antenna & no ground at it ... He was very strong using FM, was & one SSB at same time but the Delta covered the SSB so seems working good

EDIT seems once i am using the Boomerang have not heard him again but again since then was not that much propagation from France just 2-3 times & may he was not on the air or maybe me different timing

EDIT 2 this antenna seems slightly directional so maybe how the angles of the antenna to my location make it him one of the stronger contacts i had