Hi Desert Rat,
Your Phoenix stations are extremely weak according to your tvfool. When signals are right on that edge of reception, they can come and go. Where you'll notice this is during daylight hours. If at night they are stable and 10 or 11 in the morning they vanish till 6 or 7pm they are showing symptoms of what the atmosphere can do to TV signals that are very weak, the more active atmosphere is too much for the signals and they fall below reception threshold. I have a signal that is about 7db. Without my preamp in service, it vanishes for most of the daylight hours. The preamp has helped reduce that just to occasional freezes or 1 or 2 second drop outs during middays.
Your situation with FOX is unfortunate. If I were in your situation, I would swap you antenna for a two antenna situation.
First Antenna:
Channel Master 4228HD:
http://www.solidsignal.com/pview.asp?p=4228-hd. This recommended over the DB8 due to having a bit nicer gain in the channels below 35. It is also for UHF only (real channels 14 and up)
Second Antenna:
Antennacraft Y10-7-13[.
http://www.solidsignal.com/pview.asp...-7-13&ss=31606. This antenna is for high-VHF only (real channels 7-13).
You also need a combiner. The
Antennas Direct EU385CF-1 signal combiner is a nice unit.
http://www.solidsignal.com/pview.asp...CF-1S&ss=31614. This does what it says, literally. It takes your 4228 and Y10-7-13 and instead of two coaxes combines them into one. Thus, your 4228 coax will go into the UHF input while the Y10-7-13 coax will go into the VHF input, hook into your exist download into the "output" connector.
You can test a preamp, it may or not work as planned. With preamps, if you have strong signals nearby, such as KHRR RF 40, you can actually lose reception to overloading your tuner. If this happens, remove preamp.
Overall, this is what I would do to go after FOX. It still may not be reliable, but it gives you the best chance. With your 2-edge conditions for magnetic 65's towers, you need a UHF antenna with more surface area.
When mounting, make sure to have 4' of space between antennas on mast.
Cheers.