@Electron, you seem to be the only one who interprets the discussion re. low-VHF noise as "constant and never ending negative jibber jabber". As with virtually every other aspect of OTA reception there's going to be a range of opinion. Particularly when all we have to work with is a predicted signal and a limited idea of the real world conditions that go with that prediction.
In this particular example, I agree that reliable reception of KSFW-LD (CH-2) is possible. I'm with you when you add the antenna gain, 6 dB in the case of an HD7084P, thus improving the NM from 14.8 to 20 maybe 21 dB. At the bottom end of the low-VHF band, I'd like to see more margin than that because the real world NM is going to be 10 to 15 dB worse due to the RF noise present in that band. That leaves me hoping there will be at least a few dB of fade margin... the only way to know is to hang metal in the air.
However, I have to respectfully question the idea that a preamp will improve the NM any further. Are you presuming that the tuner noise figure is 5 dB higher than the preamp?
The path profile certainly appears to support your prediction that higher mounting would yield more signal. Another point of agreement... higher is usually better.
@Signals Unlimited, Your suggestion of a smaller profile antenna also has merit. It takes into consideration the existing J-pole which the OP mentioned. A larger antenna may or may not fit on a J-pole. Your skepticism re. reliable reception of CH-2 is warranted given the thin fade margin available.
@braillle, At this time,
www.rabbitears.info indicates that KSFW-LD (CH-2) is running infomercial programing and KBFW (CH-6) appears to be a translator carrying religious programing. Your interest (or lack thereof) will in those signals may be the most important factor determining your decision as to what type antenna to choose.
The point I'm trying to make here is that there is more than one way to go about picking your antenna system. If you're like me, wanting to get every possible signal, you'll need a large antenna, mounted high. If you're seeking reliable reception of just the major networks, the smaller ANT-751 will easily accomplish that and much more.