Recently I was looking for a compact 432 MHz Yagi and came across the Gulf Alpha Model 70CM-8ELFM, an 8-element 440 MHz Yagi listed for $85 plus shipping. I contacted the manufacturer and asked if it was possible to obtain this antenna cut for 432 MHz instead of 440 MHz and they agreed to ship me a prototype version to try out.
The antenna was well packed, the instructions were clear and unambiguous, and assembly was simple thanks to the well-thought-out mechanical design. The boom is two-piece but very rigid, the elements & balun stubs are high-quality aluminum rod, and the boom-to-mast mounting bracket is very sturdy. All hardware is stainless steel. I was particularly impressed by the element mounting brackets, which in my opinion are light-years ahead of the "hole through the boom, push-on compression nut" method used by some other manufacturers. The balun box has a low-loss coax balun installed and sealed to the box egress holes and a high-quality Type N female connector for connection to the coax downlead. One minor nit is that the instruction sheet does not include a drawing of the completed antenna, so I recommend taking a look at the assembled antenna's photograph on Gulf Alpha's web site if you tend to be a "visual" person and like to see an image of how the completed antenna is supposed to look. But assembly was no problem in any event.
The VSWR was adjusted to about 1.2 by moving the driven element shorting bars. At this setting the outer edges of the bars are flush with the ends of the driven element and there isn't much room for further adjustment, but Pete Mazarelli at Gulf Alpha said that lowest VSWR is typically with the shorting bars all the way at the end. (NOTE: Forward & reflected power measurements were made using a Bird 43 wattmeter.)
The catalog 440 MHz version is shown end-mounted but can be center mounted if desired and that's how I mounted my 432 MHz prototype. The extra length on the back of the boom means that the option of end-mounting is still available. Because my mast is small I needed some extra spacers so that I wouldn't run out of thread on the U-bolts before the antenna was tight to the mast. Gulf Alpha mentions this in the instructions and recommends using several flat washers, but I manufactured some 1/2-inch thick circular brass spacers on the lathe and made sure to place them between the stainless steel nuts and the stainless steel retaining bar and NOT next to the aluminum mounting plate (an old Navy trick wherein stainless spacers are used to separate aluminum from brass or bronze aboard ship to avoid dissimilar metal corrosion/electrolysis problems).
I mounted the antenna above my 2m Yagi and it is being fed with 60 feet of Air-Com Plus low-loss coax. Despite its small size I've been very pleased with the results, and while I may replace it with a larger Gulf Alpha 70cm Yagi at a later time, this one will still be great for portable use because the construction is very rugged and its small size (60" boom) makes it easy to carry in the car without any disassembly. It is also very competitively priced as there is at least one other similar-sized 432 Yagi available that is not as well built, has lower gain, uses a UHF connector and is priced a few dollars higher. Dealing with Gulf Alpha was a pleasure since they seem eager to communicate and resolve any problems.
Gulf Alpha's Internet site can be found at: http://gulfalphaantennas.com/
If you are interested in this particular antenna you will need to e-mail or call Gulf Alpha and specify the 8-element 432 MHz version as built for K4MSG. Pete will know what you need.
Best Regards, Paul Bock - K4MSG - Hamilton, Virginia
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