A "mud map" aerial view of my current set-up of antennas

ANTENNAS....BIG LOOP ANTENNAS!

(This post is an edited version of an article I wrote for "The World of Shortwave Listening" column of The Spectrum Monitor magazine - April 2021 issue. Further details on this excellent publication are available at www.thespectrummonitor.com)

It seems that these days, small loop antennas for use on the high-frequency bands are just as popular as ever. Much is being written about them, and a quick web search brings up a host of links to designs for both passive and active loops, construction issues, and forums with plenty of opinions on which loops work the best. And there are a growing number of manufacturers selling loops, including the long-established Wellbrook, W6LVP, Alpha, Chameleon, and MFJ offerings, along with any number of loops for sale on eBay.

These “loops on a pole” are ideal for the growing number of shortwave listeners and hams who find themselves in apartments, homes with strict HOA covenants, and locations where electrical noise is a rapidly growing problem. Plus, on the web, you will find many interesting designs for homemade loop antennas that are cheap to build and provide hours of experimenting fun! For the most part, many of these loops work well in circumstances where a lack of space is the reality, or where having an easily rotatable antenna can null out intense man-made noise from a specific direction.

Of course, there’s nothing new about loop antennas. They have been around for as long as radio itself! Consider the ferrite bar with fine wire wrapped around its length that sits inside most small AM radios. And I can still remember my teenage years experimenting with box loops attached to a variable capacitor for my mediumwave DXing pursuits.

Then there are the large wire loops. And I do mean LARGE! But it helps if you have the real estate to hoist these things into the air. Fortunately, we live on half an acre, so full-wave loops are achievable, although my better half draws the line at having multiple wires in the front half of the property.

The Horizontal Skyloop

Over the last few years, I have experimented with horizontal loop designs, also known in some circles as the skyloop. The first one was in a non-traditional rectangular shape and resonated around 10 MHz. It was a fabulous loop for listening because the noise floor dropped considerably compared to my dipoles and end-fed antennas. Signals just seemed to pop up out of the air when the loop was switched in, making listening an absolute joy. That was until a large eucalyptus gum tree fell on one side of it, bringing the whole thing back to earth.

Here is a YouTube video I made at the time (back in August 2017) about the early experiments with my first horizontal loop.

My next horizontal loop rose into the air about 12 months ago and is in more of a square shape with a total length of 100 meters (about 330 feet). I really like this antenna because it “hears well” across most of the shortwave broadcast bands. But it also resonates well on multiple ham bands from 30 meters right through to 6 meters with just the internal antenna tuning unit of the Yaesu FTDX3000. And, with a bit of gentle persuasion, it can also put out an SWR-acceptable signal through my external ATU on 40 and 80 meters. Although some designs for horizontal loops recommend open wire feeders, I’m currently feeding mine at one corner with a 4:1 balun and coax.

Diagram by Lars OZ1BXM (with thanks!)
Check out the OZ1BXM website: http://www.oz1bxm.dk/index.html

The Delta Loop

A few months ago, yet another loop was hauled up high. This time it was the three-sided vertical delta loop, 30 meters (98 feet) long as a full-wave antenna on 30m for my FT8 activities. Of course, it also works exceptionally well for the broadcasters in the 31m band. This delta loop is fed at the top (apex) on a single MFJ push-up fiberglass mast and tied at the lower corners to some pine trees.

Diagram by Stephen W5SDC upon which my Delta is based
(although my measurements are different)
Check out the W5SDC website: http://w5sdc.net/delta_loop_for_hf.htm

Raising it via a pulley at the top of the mast proved somewhat more challenging than I had envisaged. I had planned the three sides to be of equal length. But with the land below sloping away and the two pine trees not being in precisely the right spots, the delta’s horizontal side is longer than the other two sides. Still, the loop’s apex is at 10 meters (33 feet), and the “sort of” horizontal side varies between 3 and 4.5 meters (10 and 15 feet) above the ground. Once again, I find significantly reduced local noise pick-up on this antenna, plus I have excellent broadcast reception on 41 through to 25 meters and respectable SWR figures on the 30, 17, 15, 12, 10, and 6-meter ham bands.

Three Antennas....for now! 😏

So, between my 20m double bazooka (coax) dipole, the square horizontal loop, and the delta loop, I now have coverage across nearly all HF broadcast and ham bands, with options to switch from one antenna to another depending on the signal direction and local noise issues at different times of the day. All I need now is to work out how I can fit in a 160m antenna and keep the XYL happy by not invading that sacred front half of the property!

So, if you live in a home with some space around it, consider trying some full-wave or large-size skyloop antennas. A quick web search will access heaps of information on all types of loops, both big and small. Have fun building and experimenting with antennas. And remember that the fanciest of receivers won’t work well unless you put some research and effort into a high-performing antenna system!

73 and good DX to you all!

Rob Wagner VK3BVW