The Coymel Stealth VHF Yagi

A 144 MHz antenna from Swiech Communications Systems.

While doing some cEeanup this pasi spring in my amateur radio "barn* (a small shed in my back yard full of masting, antennas and coax), i came across an ofd, beat-up. bent dented and otherwise Cashable KLM four-element 2 meter yagi I ve owned this particular antenna tor about 14 years and it has really been through the nnger. accompanying me on over a dozen mountaintopping trips, more than a few Field Days, and several public service events.

It got me to wondering if anyone made a really durable yet portable yagi for yeoman 2 meter service—as a temporary link antenna— for Field Day use or the odd mountaintop tnp. This "ideal antenna would have to be fairly lightweight yet very durable and take a minimal amount of time to assemble in the field. "Dream on," J thought until 1 made the rounds at Dayton last year!

The COY2M3EL "Stealth"

This nifty three-element 2 meter beam caught my eye me minute I walked past the Swiech Antennas booth: It's jet black with

Steel hardware and nickel-plated connectors and really resembles something from the Air Force's "stealth" technology program. The boom is round like most conventional yagis. and the elements mount to the boom with a composition block that attaches wJth a single bolt and wingnut Black end caps and protective tips on the 1/4*-thick elements finish off the professional appearance.

The "Stealth11 measures 38"—quite a bit shorter than most small 2 meter yagis I've ever used, but also heavier by at least a pound, indeed, the Stealth" is a very substantial antenna and I have no doubt of its ability to survive severe weather in a permanent installation. However, the slight increase in weight does make a difference when you tug it around for some time in a portable application, so Gene Swiech W89COY recommends this antenna (and its 440 MHz companion, not reviewed) for temporary and permanent point-to-point link operations

Assembly of the COY2M3L is very simple— you just slide each element and its mounting block onto the boom, center them over the mountrng holds, and insert a stainless #8 screw and wingnut to fasten it. Gene also intended tor the COY2M3L to be carried in a standard nylon zipper bag, hence the protected element ends and boom caps. The boom-to-mast clamp fastens directly through the boom with a single U-cfarnp, and you can opt for either vertical or horizontal operation.

Performance

Swiech claims 6.1 dBd (over a dipole) gain for the yagi, and while I couldn't accurately verity this number 1 did lake a look at Ihe pattern and VSWR using a simple test range with a 2 meter source and whip antenna several wavelengths distant. At 45 degrees either side of the test signal, it was reduced by 2.5 dB while at 90 degrees, the signal was down by 16.5 dB, and the fronHo-back ratio clocked in at 10 dB—adequate for foxhunting or link work.

The feed <s a gamma match design, which usually results in a narrowband match with corresponding hi-Q response. I swept the antenna Irom 140 MH2 to 150 MHz, showing 2:1

Simple Gamma Match

Photo li. Close-up of the #amma match element mourning block.

Photo A. The Swiech COY2M3EL vagi 44 73 Amateur Radio Today • June, 1995

Photo li. Close-up of the #amma match element mourning block.

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