Sorry for the typo on the RCA 751. I live in an aluminum mobile home with a steel roof, so an indoor antenna is not at all feasible.
TV Fool is not entirely correct for El Paso. As I alluded to above, KVIA is in the process of moving from RF 7 to RF 17. 17 was the pre-transition frequency and was quite reliable after they got beyond the 1 KW start-up phase. Both 7 and 17 have been available for at least two years now and at least in my location 17 is much weaker. RF 7 shows a signal quality on the Tivo of about 74 and SNR around 26, but it continually fluctuates like KCOS does. RF 17 has a signal quality of about 48 and SNR of 22, but is very steady. Last night I switched to the 17 version of KVIA and made it through both the ABC and local news without any break-ups.
KTSM is also switching from RF 9 to RF 16, again their pre-transition frequency. Tivo thinks that KTSM is only available on 16, and although I could scan in the RF 9 version I have not as their would be no guide data and recordings would have to be manual. Besides, I figure as they are going to the RF 16 permanently, I may as well use it. That said channel 16 also fluctuates continously, but with SNR's in the range of 24 to 31 I have never seen a problem with that signal.
I too am thinking that this is primarily a VHF problem, in that the worst offenders are RF 7 and 13. The channel 17 signal is just weak, they may not be operating at the power indicated by TV Fool. I will continue to hope for better results on 17 for KVIA however. As for my PBS, of which I am a member and long time supporter, I may have to look into the possibility of bring in KRWG from Las Cruces. I have received channel 23 before, but have not made much effort since they went digital. That would be another project for another day.
In the final conclusion, it is very disappointing that Tivo put such a poor OTA tuner in what otherwise seems to be a very good DVR. I realize there are challenges to my reception location, but I have no problems with my six year old Sony KDF-37H100, nor do my neighbors who have a "Polaroid" flat screen and an old Radio Shack VU-90 antenna that I gave them.