Re: FSL Antennas-- Truth and Fiction

Andy ZL3AG

Good article Gary.

A couple of suggestions...

Mention the fact that Graham is now deceased, and also that he published some very good loop antenna designs in Practical Wireless magazine in the 1980's.



On 4/10/18 10:02 PM, @dxergary [ultralightdx] wrote:

The development of modern Ferrite Sleeve Loop antennas has been one of the most remarkable antenna breakthroughs of the 21st century, but since none of these have ever been mass produced for commercial sale, a lot of questions and misconceptions about their function and effectiveness persist in the general AM-DXing community. This brief message is an attempt to clear up some of the more common misconceptions.

Modern FSL antennas are based upon an experimental article published by the U.K.'s Graham Maynard in February of 2011, describing a cylindrical collection of ferrite rods wrapped by a wire coil, and tuned by a variable capacitor to resonate with (and provide an inductively coupled gain boost for) a nearby portable radio tuned to the same frequency
Graham's original article included quite a bit of "unusual" scientific theory (for which he was roundly criticized) and provoked accusations of design plagiarism and exaggerated performance claims. Flying "under the radar," however, three dedicated antenna experimenters in the relatively new Ultralight Radio enthusiast group (Steve Ratzlaff, Kevin Schanilec and yours truly) began extensive, all-out experimentation in the new FSL design to test it out in the "real world" of ocean coast transoceanic DXing-- both on Longwave and Medium Wave.

Steve, Kevin and I shared information on which components were the most effective, and which designs seemed to provide the highest gain. For a brief time we all worked toward the goal of maximum gain, purchasing huge lots of 200mm x 10mm ferrite rods from the Ukraine (to the delight of the eBay sellers, who must now be enjoying early retirement). Of course we didn't all agree on the design factors influencing maximum gain, but one thing was becoming very obvious--
this new antenna had a compact gain advantage like none other in radio history.

Given the fact that this new antenna could provide tons of gain from an extremely small "footprint," I knew that this innovative antenna finally provided an ideal chance to test out a fascinating new theory that I've always believed in-- that an ocean cliff's flat shape could enhance transoceanic DX reception far beyond that possible on a nearby flat ocean beach. In early 2011 this idea was laughed off by almost all of the transoceanic DXers, who had routinely set up their huge broadband antennas on flat ocean beaches for decades. Nobody had ever tried a serious DXpedition on a plunging ocean side cliff, since there wasn't enough space at such sites to set up a "serious" broadband antenna-- or so they thought. But they were about to be proven wrong.

An early 8" (20cm) diameter FSL antenna was set up at two plunging Oregon coast cliffs in the summer of 2012-- at Rockwork 4 (near Manzanita), and at Cape Perpetua (near Yachats). Immediately the new FSL antenna began receiving multiple New Zealand stations that had never been heard on the North American west coast, including 531-More FM, 585-Radio Ngati Porou, 765-Radio Kahungunu and 828-Trackside. Perseus-SDR DXer Chuck Hutton was interested enough to join me for a July 2014 Rockwork 4 DXpedition, during which the all-time Grayland record for New Zealand reception was completely shattered-- 88 Kiwi stations (compared to 61 at Grayland). Chuck's broadband antenna was a tiny version of the Grayland monsters, but ocean cliff propagation enhancement more than made up the difference.

A side effect of the ocean cliff "Monster FSL" development was, unfortunately, the "expensive and heavy" reputation that currently ligers in the AM-DXing community. It was commonly joked that these new antennas could "shut down an airport without really trying," that a body builder would need to deploy them, and that they were far beyond the means of the average DXer. In late 2016 a new type of compact, lightweight FSL was designed to dispel all of these misconceptions, however-- the "Frequent Flyer" FSL antennas.

Even though the new antennas had proven to be the ultimate compact gain performers, it was a radical design concept to shrink the antenna down to a miniature size for TSA acceptance, while retaining enough gain performance to be a real thriller on exotic ocean beaches. The construction cost would need to be acceptable for the majority of DXers, and the design would need to survive a lot of travel abuse. In late 2016 two new "Frequent Flyer" FSL designs were finally built, and throughout 2017 Craig Barnes and I tested them out in thrilling Hawaii DXpeditions, tracking down all sorts of exotic Pacific island DX. Pete Taylor took one of the models on European and Caribbean cruises, and in April I had the hobby thrill of a lifetime in the Cook Islands, tracking down long range AM-DX stations in India (over 8,000 miles), Bangladesh, Mongolia, Cambodia and Brazil-- all with a radio and antenna that easily fit within hand carry luggage.

In an effort to make these compact, TSA-friendly FSL antennas available to more DXers there were 10 models given out last year, and a full "Heathkit-like" construction article for the 3.5 inch "Baby FSL" model was written, and posted at
More resources and refinements will be devoted to these "Frequent Flyer" FSL antennas this year, with the goal of making these breakthrough models accessible to all interested DXers. Whether your preference is to chase long range DX on an exotic ocean beach or simply have thrilling portable DXing sessions close to home, this new type of antenna may be your ticket to increased hobby excitement.

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)


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