We live 45 miles north of Fort Wayne. I have noticed the same thing. Channels 15 (CBS), 21 (ABC), and 33 (NBC) are usually close to 100 on signal strength. Channels 39 (PBS) is a little lower. Channel 55 (FOX) is just on the verge of being able to be seen at about 70 for signal strength and 15 dB. Ironically, when 55 lost Fox to 33.2 two years ago, we had no problems with 55. The signal drop seems to have happened since they got Fox back this past March. They (55) claim they are not experiencing any problems - even though there are been articles I have found online that discuss the drop in strength.
The site TVFool.com says 15 (real 31) is 22.4 db and -68.4 db power, 21 (real 24) is 22.3 db and -68.5, 33 (real 18) is 22.8 db and -68.0, 39 (real 40) is 17.8 db and -73.0, and 55 (real 36) is 18.4 dB and -72.4. Both 39 and 55 are at 206 degrees and 40.6 and 40.3 miles respectively. But I almost never have problems picking up 39.
Also, on a regular basis, I can pick up South Bend stations 16 (real 42) listed as -4.1 dB, -95, 66.7 miles away at 273 degrees; 22 (real 22) listed as -6.1 db, -97, 66.9 miles away at 274 degrees; and Battle Creek/Kalamazoo channel 41 (real 20) listed as -7.4 dB, -98.3, 69.0 miles away at 342 degrees. Why these stations when there are several others listed as being closer with higher signal strength?
That Yagi antenna is one unique design. The Clear Stream 4 has are greater distance for only about $12 more (
http://www.amazon.com/dp/B001BRXW74/?tag=satell01-20). I have an old UHF only antenna with a 22 dB preamp. I changed the preamp, but the antenna is the same one that was at the house when we moved there 22 years ago.