How the HD signal is deteremined?

I read somewhere it's derived from satellite radio (XM)

 

There is a nice discussion in the Gen-1 PiP forum that discusses this: XM Data Finally Expired | PriusChat

I saw the traffic alerts in my Prius Prime Plus navigation screen about two months ago but didn't know how the data was sent to the car. I get the impression the High Definition (aka., digital broadcast radio) was the source. I didn't know there was a car based App that might have more data. I'll go look.

Having a warning about traffic problems is a good thing but only if there is a way to tell if the car is getting the signal. Otherwise, one might expect this aid help only to get stuck in a traffic problem.

Bob Wilson

 

I live in a suburb of Los Angeles where, for instance, KNX 1070 (Newsradio) is an HD Station. I do NOT have XM radio at all. Just yesterday in my Prime Plus, I was pressing the Weather buttons to get weather information, and at the bottom of the screen it indicated that it was getting the weather information from the HD Radio signal. For traffic, I'm not sure, but if I remember right, it mentioned somewhere in the manual or somewhere that it gets it from HD as well.

Two things about HD: (1) apparently it takes a couple seconds to "handshake" and go HD, it's not instant. So when I tune to KNX, the first 5-10 seconds sound like normal AM audio, then all of a sudden the HD comes on.

(2) However I don't know how much more signal HD needs than normal AM, because just yesterday as I was driving (open area, around Orange County, only about 40 miles from LA) the signal would keep reverting back to normal, then HD, then normal, then HD, then normal, etc. -- and KNX is the highest power station that the FCC allows, and there was certainly no problem with signal strength (at least as far as normal AM goes). I've only listened to the AM radio 3 times since getting the car, so I don't know if (a) this was a fluke, or (b) HD requires a lot stronger, solid signal than normal AM. I will say, that when it was going back and forth, the normal AM signal was really strong, and those who live in SoCal know how strong KNX's signal is, so I don't know what caused it the other day. The other previous 2 times were fine.

But as far as your question, I can tell you the weather comes from the HD Signal (as that's what my radio shows when fetching weather info)... and for traffic, I seem to recall reading that it was HD as well...

 

Today I was fiddling around with entune and got it to update the in car apps. The weather app now gives local conditions.

For now, I don't see an entune advantage over playing audio via USB. Both will tap my cell phone data plan but entune seems to 'stove pipe' the sources.

Bob Wilson

 

HD radio is not satellite radio. It is a digital transmission from a local station. (And it's not high definition--HD is just a name.) Some think that conventional analog FM radio has better sound qualities than HD, but the analog can be scratchy in weak reception areas. HD just goes silent when the signal is weak.

 

"HD Radio" can be piggybacked on either AM or FM. As mentioned, "HD" is something of a misnomer; all it really means is that it is digital, and it can carry the station's main audio feed, a secondary program, and pure data, such as traffic and weather info. One of the complaints about the Sirius /XM traffic data on the PiP was that it tended to be terribly out of date, at least partly since you had to wait until the satellite got around to your region in the continuous stream of the traffic info. (That was certainly my experience.) I don't know how the navigation system finds what frequency the traffic info is on in a particular area. You don't have to have the radio turned on to get the traffic info.

 

Source: HD Radio - Wikipedia

Digital information is transmitted using OFDM with an audio compression algorithm called HDC (High-Definition Coding). (HDC is a proprietary codec based upon, but incompatible with, the MPEG-4 standard HE-AAC). HD Radio equipped stations pay a one-time licensing fee for converting their primary audio channel to iBiquity's HD Radio technology, . . . ​

Ok, we'll call it HDC instead of HD. <groan>

Bob Wilson

 

my other cars (2 other) detects an hd2 and hd3 station, but the prime doesn't, even when I drove within 10 miles of the transmit tower. anyone else have similar problem? also the antenna is noticeably getting worse reception than my other cars.