VE6AB Portable Ops
Magnetic loop versus the Dipole
So miles (kilometers) down the road, after building the MLA (Magnetic loop antenna) pictured here, as well as a second one not shown here, the tests have confirmed it, the MLA more than holds its own on 10 through 30 meters when compared to a dipole.
Now the results change somewhat when operating on 40 meters, as small portable loops such as this one are at a disadvantage on 40 meters and lower, although I've made many contacts on 40 meters.
Now if I were to build a larger MLA that would allow me to work 40 through 80 meters, the results would prove to have a different result, with better efficiency on the lower bands using an MLA better designed for the lower bands.
Now lets be clear, most MLA's of the size shown here, are built for their portability and very small footprint.
When I drop my manpack on the ground (or snow), and pull the MLA out of the storage bag located at the rear of the manpack, I am working the bands in less than 2 minutes.
When I bring along my 10 through 60 meter vertical, it takes me more time, as once the antenna is assembled, I still need to lay out the 6 ground radials part of the vertical antenna.
The real practical advantage of the MLA, compared to my vertical antenna with its ground radials, is the MLA’s freedom from dependence on a ground plane and earth for achieving efficient operation.
The beauty of the MLA is the fact the only elevation required above the ground is one or two loop diameters, and its good to go.
Also, there seems to be a fallacy that MLA's are critical to tune, and nothing could be further from the truth.
The problem is that most guys don't take the time to correctly choose the variable capacitor used in the construction of the MLA.
The secret, and there is no secret, is if using a butterfly capacitor in constructing your MLA, is to add a geared drive to the front end of the variable capacitor, and you will be pleased with how easy it is to tune the MLA.
Geared drives are very inexpensive if the variable capacitor you plan on using didn't include one.
For example, once the MLA as seen here was ready to go, and on this morning I was working 20 meters with the band in excellent shape, once I chose a station I wished to work, and quickly adjusted the variable capacitor for maximum signal, I dialed off 10 kHz, placed the 897 in key-down mode, and adjusted the variable capacitor for the lowest SWR shown on the meter of the 897.
Back on the calling frequency, I made the call to Alfred AF5VH located in Albuquerque NM who had been calling CQ, and Alfred picked me up immediately.
It actually took longer to describle the procedure, than to actually tune up.
So there you have it, and yes I love the MLA design to the point that I have drawn up a set of plans for a high power 10-80 meter rotatable magnetic loop with remote tuning, a high-performance MLA capable of more than able to hold its own on the low bands, yet having a very small footprint when mounted on the roof of my home ham shack.
Beautiful March morning out in the foothills bordering the Rockies, and with the temperature on the plus side of freezing, and the melt happening, spring was in the air!
Expand the photo for a closer look.....
A closer look with description of the 10 through 40 meter MLA .....
http://www.jerryclement.ca/MachineShop/Antenna-Werks/i-WHQvdc5
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