The Boonton microwattmeler hanging below the boom of the "receive" 55-element Yagi. ItsRF detector is up by the boom, inches from the driven element.

Detail of the ' 'receive'' antenna feedpoint with the Boonton microwatt RF detector head coupled to the short RG-213/U pigtail. We assumed the pigtail to be lossless.

Bird Thruline wattmeter hanging below the boom of the "transmit" 55-element Yagi. Its RF coupler is up by the boom, just inches from the driven element.

the "polarity" of each driven element is in­dicated by a "bump" in the plastic dipole in­sulator. This polarity indication is not impor­tant for anyone contemplating a single Yagi in­stallation, but it is handy for those considering a stacked array. As the F9FT instruction sheet warns, "During mounting process on the stacking frame, make sure antennas are prop­erly phased. The bump on the plastic shell of the driven element marks the outer conductor of the feedline. All the bumps must face the same side (all left or all right, in horizontal polarization)." I guess this says it all.

The instructions offer stacking information and the part numbers for commercially avail­able (Tonna-manufactured) two-port and four-port 23 cm splitters. The manufacturer also in­cludes a discussion on antenna mounting, pointing out that most antenna masts are of a diameter which approaches one-quarter wavelength at 23 cm (40 to 54 mm). This means you cannot allow the antenna mast to pass through the plane of the elements! Ton-na recommends their 23 cm antennas be mounted at the very top of their mounting masts for maximum efficiency. This is easily accomplished in four-bay stacked systems us­ing an " H " frame.

The 55-element 23 cm Yagi, like other Ton-na products, is supplied with a high-quality type-N connector for assembly to the coaxial "pigtail," and a spare reflector element which can serve as a replacement for any passive element in the system.

Alright already! How does it work? In a word, I'd say "GREAT!" Before even installing the connector on my 55-element Yagi, it was loaned out to Dave Collins, K2LME, who was going to use the antenna for the ARRL September VHF QSO Party at multi-op station K2DEL. The group at "DEL" installed the antenna atop their mast at a rather average location in northeastern New Jersey, where they ran a whopping 3 watts to it for the con­test weekend. Results? They made 15 con­tacts on 23 cm, including one with W1TKZ/1 in VT, 200 miles away. This is nearly 70 miles per watt, not bad for 1296 MHz under "flat" band conditions. I think they could have done even better, but their operators were totally un­familiar with 1296 MHz operation and were pretty much flying by the seats of their pants.

Dave returned the antenna to me the follow­ing week, and Pete and I got together on Sep­tember 22 to build an "antenna range" which we hoped would allow us to measure the gain of these products by an indirect but proven procedure. The details of our test plan were contained in the December 1985 column, but I'll include a summary here as well. There is a way in which antenna gain can be calculated after a measurement of recovered signal over a known path from a known source is made. This technique is not exactly new, having been described by C.G. Montgomery in his article "Technique of Microwave Measurements" published in 1948 as part of the M.I.T. Radia­tion Laboratory Series. Antennas are oriented directly toward each other at an appropriate distance in the far-field region, and measure­ments of transmit power, received power, and antenna separation are made. Assuming ab­sence of reflections and obstructions, the data collected can be applied to the formula shown in fig. 1 to determine total antenna gain (for both antennas).

This figure doesn't do you much good, un­less you know the gain of one of the antennas with some degree of accuracy. However, you needn't know even this much, if you use two

Say You Saw It In CQ January 1986 • CQ • 63