Wednesday, 8 May 2013

An introduction to the LFA-Q for 70Mhz.

A 4 element low-noise, High Gain LFA-Q Quad Style Yagi for 69.9-70.5MHz
MASSIVE Gain for a very compact boom size
Gain: 10.62dBi @ 70.2MHz
F/B: 25.34dB @ 70.2MHz
Peak Gain: 10.71dBi
Gain 10m above ground: 16.38dBi
Peak F/B: 25.88dB
Power Rating: 5kw+
SWR: Below 1.4.1 from 69.9MHz to 70.5MHz
Boom Length: 2.6m
Vertical Stacking: 3.75m

The LFA-Q (Loop Fed Array Quad) Low-Noise Yagi takes a lot of the good points from the LFA Yagi and adds some more. the LFA-Q is a quad with a difference. Rather than placing symmetrical square or triangular shaped loops in a Yagi configuration, the LFA-Q uses the LFA Yagi style loops to produce high levels of side suppression, the difference being every element is a loop rather than just the driven element.

The shape of the loops have been formed (compressed) until the short side sections are exactly 180 degrees out of phase with one another and therefore, a cancellation effect occurs in much the same way as balanced line feeder works. This means high levels of suppression to both the sides and the rear of the antenna can be achieved.

So if the LFA Yagi does this so well, why do something different with loops forming all elements? The primary reason is gain per meter of boom on a full wave element antenna can be much greater than on a half wave element antenna such as the LFA. This results in compact, high gain antennas which are constructed to stand some serious weather conditions!

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