The Saga of the Shared Apex Loop Array (SAL-20)

The finished product.

Back at the Dayton Hamvention in 2013, Array Solutions debuted a new compact receive antenna system called the Shared Apex Loop array, or SAL. Building upon the foundation laid by the EWE, K9AY, and the flag and pennant antennas, the SAL featured true time delay phasing, and no need for a control wire from the shack to the antenna or grounding. Best of all, if the plots and modeling were any indication, this antenna might actually live up to the promise of Beverage like performance in a small lot.

This last weekend, after being flooded out the last time I tried to put it up in July, I took advantage of what may be our last good weather of the year and got a SAL 20 up and running in my yard. It wasn’t easy, but its up and receiving signals.

My make-shift soldering station.
My make-shift soldering station.

Since the wires that came with my antenna had a close encounter with the lawnmower, I needed to cut new ones to make into the four loops. According to Array Solutions, they recommend 62′, but a little longer is fine as long as all the wires are the same length. With this in mine, I cut four lengths of wire each 64′ in length, using up the rest of my 12ga wire minus an 11″ remnant.

After that, I went ahead and fed them through the mas before feeding the couplers, an insulator, and a shrink wrap tube over the wire before tinning them. There’s a reason soldering is not listed on my resume as a skill, but I did ok, and sealed the joints with the shrink wrap after I was done.

The mast is up, held in place with two ‘shepherd’s hooks’. Note the wires taped to the mast to keep them from getting tangled (again).

Now it was time to get this beast up in the air, and here’s where I met my first obstacle. I managed to tangle my wires up pretty good while I moved the antenna over to where I’d be putting it up, and I ended up having to cut them and start over. This time though, I didn’t solder them before setting the mast up. Instead, I taped them to the mast at the base so that they wouldn’t get tangled again, and soldered each one individually.

Now that I finally had it up in the air, I went and put the stakes into the ground and tied each loop down at the corner, forming four triangles at right angles to each other. Since my dog bone insulators didn’t show up until this morning, I improvised and used inch long sections of PVC pipe. They’re cheap, they were available, and the antenna won’t care.

A close up of the magnetic coupler.
A close up of the magnetic coupler.

Once everything was in line and tied down, I measured out the distance for the couplers from the center mast. According to Array solutions, Each coupler should be about 86″ from the center of the mast with the positive lead facing outward. Using a measuring tape from the base of the mast, I lined up each coupler so that the center was at the 86″ mark. This will need a little fine tuning before its a finished product, but it’s a good starting point.

DX Engineering’s crimping tool for the win!

Now that everything was positioned properly, I wired all of the couplers up to the central ‘junction box’, and attached the delay cable. After making quick work of a coax run to the shack (thanks to DXEngineering and their awesome F type connectors and crimping tool), it was almost time to see if this antenna was worth the effort.

Of course, as with most of my projects, I came up a cable short. The control box for the antenna uses an RCA out jack, while everything I own is either an N or SO-239. Time to break out the soldering iron again, and one sacrificed RCA cable and a PL-259 pig tail later, I had a crude but effective RCA to PL-259 cable.

The 'finished' control box that needs to be cleaned up a little.
The ‘finished’ control box that needs to be cleaned up a little.

Now by this time it was already dark, and the instructions do not recommend trying to optimize reception after sunset. I still wanted to see what this antenna could do though, so fired up the Perseus and I went about putting the new antenna through its paces. Some of my initial tests were kind of disappointing, like my inability to null out the nearby KASI on 1430 (the same station I tested the Pixel Loop out on last year). On other frequencies though, I could hear a different station with each direction I chose, which is pretty cool.

Later on in the evening, I saw a post about Magic Lantern International, a Euro pirate, relaying a show on 6205 kHz. While my copy on them wasn’t very strong, they were strong enough for me to identify the music being played and catch a ‘Laser Hot Hits’ (the station they were relaying) ID. Just out of curiosity, I fired up the Elad through my secondary long wire to see how it compared. The Elad and the long wire didn’t catch a trace of them. The SAL-20, pointed to the Northeast, had a listenable copy, while the 75′ long wire couldn’t even catch a whiff.

While this antenna is still a work in progress, this beast shows an awful lot of progress. I not only heard VL8A and VL8K this morning, I also heard a very loud and listenable signal from North Korea as well. Even better than that though, I saw some faint traces of carriers from Asian mediumwave transmitters. That’s not much to go on, but it’s more than I’ve seen from any foreign mediumwave signal before.

All in all, this is shaping up to be a fantastic DXing season.