I just noticed a change to how virtual channels are mapping into my Zenith DTT900.

We have two essentially identical NBC feeds available to us here. One from KXAN (36-1, RF 21) and a closer one from KXAM (14-1, RF 27). The latter is basically just a second transmitter for the former's programming. In the past, when the DTT900 tuned, it would find RF 27 and map it to channel 14-1. But lately, it has mapped RF 27 to 36-1 AND RF 21 to 36-1 as well! The net effect is that I show two channel 36-1s in the guide -- and no 14-1 any more.

Is that likely because of something they did at the station (i.e. with PSIP data(, that maybe since the programming is the same, they just wanted everything to map to 36-1, both the RF 21 and RF 27 signals?

Yes. The mapping is done by the station and it sounds like for branding purposes, they changed the PSIP mapping to 36-1. According to the FCC they can't do that, unless they have a waiver to do so,

Yes. The mapping is done by the station and it sounds like for branding purposes, they changed the PSIP mapping to 36-1. According to the FCC they can't do that, unless they have a waiver to do so,
Interesting. I just reset the Zenith in the bedroom where I only have a small set-top antenna that picks up only two RF signals (13 and 27). These have corresponded to 62-1 and 14-1 respectively. But now they show in the guide as 62-1 and 36-1. This would seem to confirm that their information has indeed changed from 14-1 to 36-1.

I suppose they figure since the programming is now identical from both transmitters, they might as well map everyone with reach of either signal to the same virtual channel 36-1 -- since it is the same "product" on both frequencies. I guess it's not a big deal but it can be confusing to see 36-1 appear twice if you can get both signals. My D* HR20-700 still shows 14-1 and 36-1 but I wonder if that will eventually change there as well.

Is the RF27 a low power translator? Can a translator map to the same virtual channel as the parent station, or does the FCC (stupidly) require them to map to the translator's legacy analog channel? In Fresno KVPT PBS is analog channel 18 and digital RF 40 virtual 18. Here in Bakersfield they have a digital translator on RF 18 (yes, the same as the parent station's analog channel). It maps to virtual 18. They also have an analog translator on channel 34. Surely they are not legally required to map RF 18 to virtual 34.

Is the RF27 a low power translator? Can a translator map to the same virtual channel as the parent station, or does the FCC (stupidly) require them to map to the translator's legacy analog channel? In Fresno KVPT PBS is analog channel 18 and digital RF 40 virtual 18. Here in Bakersfield they have a digital translator on RF 18 (yes, the same as the parent station's analog channel). It maps to virtual 18. They also have an analog translator on channel 34. Surely they are not legally required to map RF 18 to virtual 34.

On channel digital translators are not required to regenerate PSIP metadata and can just pass through the main transmitter signal. I know on satellite stations they are required to regenerate PSIP that matches the satellites analog channel on their digital channel. Translators, I am not sure on. I don't think I have ever seen what the rules are on that, but then I have never looked since my station doesn't have any translators.