Quote:
Originally Posted by Billiam
Thanks. It is now more apparent that yes indeed the problem is a combination of signal strength and interference from a co channel.
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I made a mistake on the 34" distance. I read the left side UHF distance for the third null. I should have read the right side VHF for the first null.
After a closer look there are two channel 7 co-channel stations. KHQA is almost as strong as KOAM.
The difference from KQTV to KOAM is 111°. The difference from KQTV to KHQA is 124°. To use the graph on the ganging page of the HDTV primer it's necessary to use the angle off the back of the antenna, so the angles become 56° and 69°. To split the difference the correct distance is for the first null is 3.2' or 38.4". 34" should have helped, but 38.4" will be better.
Also note that the two baluns must be connected with the same polarity. I've never seen a balun with the polarity marked, but you must have resolved that problem when you stacked the antennas one above the other.