cowboyup4christ

Piggie

I have used these antennas as well and they are only out classed by single channel yagis that cost 4 times as much. Excellent antenna and at a very good price indeed.

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I have also stacked a pair of these for even more gain. One paper my method of stacking should only yield about 2.5 db more of gain. In my practical results, it seemed like a lot more than that, once I found the best stacking distance.

I placed the two antenna in exactly the same direction on a mast, one above the other. Be as close as exact as possible.

I then spaced them 40 inches apart to cover the range of ch 7-13.

I used two 4 ft pieces of coax from the same roll, cut just as close as possible to exactly the same length as possible (more critical than the 4 ft length). Again, they can't be two pieces you have lying around, cut them from the same piece of coax.

I placed a Winegard CC 7870 2-Way Antenna Joiner Coupler which will mast mount between the antennas and put both into the ports marked Set1 and Set2. Then the one marked antenna into an amplifier. (CM7777 in my case).

Note that the specs say this combiner is 3.5 db loss. That seems like it would negate the 3db theoretical gain of stacking two antennas. But if the two joined antennas are both facing the same direction, 3 db of the loss approx is canceled leaving about 0.5 db loss through the combiner. Hence the 2.5 db gain on paper.

I believe the real world improvement I see over just one has to do with the angle of the signal. I am not Line of Sight to the VHF towers, but 2 edge refraction. Stacking the vertically does not change how they aim, left to right or clockwise or counter clockwise. It does though narrow the beam vertically (like they are stacked) so less signal goes up in the air and less signal goes at the ground. Instead the combined antennas pick up signal more so right at the horizon, which is where normally it is strongest coming over an obstacle.

I built this system before Winegard came out with the 7698P antenna, which has just as much gain as my stacked array. Still this is my best choice, as my VHF stations are to the north, and all my UHF are too the west, making it not need a rotor as if I had replaced it all with a 7698P (which is a remarkably good antenna itself).

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The more I understand, the less I know.