One of the problems with reception of VHF-Low channels is the high noise level from electrical interference. It's even higher than on VHF-High, as I showed previously with my noise level measurements. The signal must be at least 15 dB above the noise to be received.
I don't have any VHF-Low channels in my area, but my noise level on VHF-High causes interference to my weak marginal channel 9 signal. Sometimes I can receive it and sometimes not, depending upon the signal strength of 9 and the noise level at that time.
When you do a channel scan, sometimes you don't pick up a channel. If the tuner doesn't pick up the channel, you don't know if it's because it's too weak or it isn't there. In the past, it was necessary to use a signal level meter or a spectrum analyzer to find out why. A spectrum analyzer is expensive, but now inexpensive SDR dongles are available to use as a spectrum analyzer with the proper software. I bought an RTL-SDR.COM dongle to look at my VHF-High channels:
The software doesn't come with it; it is necessary to assemble the software in a folder to get it to work. I have been downloading and installing software for almost 20 years, but this was a challenge for me. I finally got it working and this is what my VHF-High looks like:
As you can see, channel 9 doesn't quite have 15 dB above the noise for reception.
I have been helping another poster who was having trouble with VHF-High reception. We suspected that his noise level was high from electrical interference, but we didn't know until he did a scan with his SDR dongle and spectrum analyzer software:
You can see very strong electrical noise interference, but he hasn't found the source of the interference yet.
So, it should be possible to use the SDR dongle and spectrum analyzer software to see how high WQED on real channel 4 is above the noise level at your location.
Good tutorial on SDR dongles by Pete Higgins:
Inexpensive Software Defined Radio Spectrum Analyzer < $10.00
Spectrum auction nets nearly $35M for two Pennsylvania stations
by Dru Sefton, Senior Editor
February 10, 2017
WITF-TV in Harrisburg, Pa., will use $25 million in spectrum auction proceeds to bankroll three new initiatives, including a possible statewide news organization. And the $9.9 million going to Pittsburgh’s WQED for shifting to another frequency could possibly retire the station’s longstanding debt.
At WQED, the cash comes from an agreement to move to a lower VHF frequency. The move “will be seamless to viewers,” it said in its announcement Thursday.
It doesn't appear to be seamless for OTA viewers.