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HD radio

2K views 11 replies 6 participants last post by  BLK GXP 
#1 ·
#3 ·
This appears to be a Metra product.. at least that's what I gather from their website:

http://www.axxessinterface.com/default.aspx

The main difference is this includes an HD Radio tuner.. the GM unit does not.

Just remember.. HD Radio is simply digital... HD does *NOT* stand for High Definition like in TV. Sneaky stuff.. but check it out if you don't believe. In fact, the ads are careful to never mention High Def... just the letters HD.
 
#4 ·
Being digital though permits the ability to fit more data in the same stream that was analog before allowing for higher quality audio at least then normal AM/FM radio. I'm not sure, but they could even offer Dolby Surround possibly if the stream could handle enough data.
 
#5 ·
HD radio stands for Hybrid Digital radio.

The US uses IBOC which uses a sideband to transmit the digital signal. For FM, stations are allocated their normal FM-frequency and use a side band in the 100MHz range to handle the digital audio signal at 96-128kbps and also a data signal of 64bkps. This allows them to transmit traffic data in addition to compressed music streams that are equivalent to the quality you'd get out of MP3s or Apple AACs; I don't know the compression used in IBOC since it's a proprietary system. However, you can't fit a surround-sound signal onto a single FM-HD channel. Multi-channel bonding would be necessary and I don't think it exists in the current spec. Most of the radio stations don't mind, since they're sold on the ability to have additional audio channels due to the smaller spectrum requirement and also include extras such as stock tickers or traffic data. AM works in the same way, but uses lower bit rates due to less available bandwidth and lower signal strength.

The European and Canadian standard is DAB & DAB+, and is much more feature-rich. They do have surround capability and use MPEG-1 or an AAC-derivative compression. I don't know if there's a data signal also included for each station, but overall the system is a little better put together; Europe has been taking a more methodical approach to converting TV and radio over to digital, and will probably do both at about the same time, with signals in the same block of the spectrum. Essentially they're chopping up the spectrum and giving broadcasters large bitstreams for them to turn into multiple radio or TV feeds. The US, however, is shooting forward with our three-block system (AM, FM, TV) because the FCC and Feds are salivating over the fees that can be collected from the spectrum resale made possible by converting from analog to digital. We're making more missteps, sure, but the pressures here are greater.

As far as sound quality - it is better. Is it worth a couple hundred bucks? Eh, to me it's not. I did a setup of this stuff for an uncle on his home stereo and it certainly sounded like a CD. The problem, though, are the crystal-clear commercials and the fact that no local stations play the music I listen to, being electronic/industrial and blues/jazz. The HD classical is nice, but country drives me nuts, as does rap and the modern alternative rock. XM remains my preferred solution.

Almost all major car streo mfgs sell this equipment, and most receiver modules cost about $100. The one you're looking at above just has a nice box to consolidate multiple digital sources into the single input to the OEM stereo. I have no experience as to which is better than any other, as my own experience is limited to one home unit.

Last, but not least, know that HD radio will eventually be mandatory. The Feds want to recover the existing bandwith and resell it as they're doing with HD video. However, we may not be using the current IBOC standard at that point, as broadcasters want better bitrates or compression - essentially anything to offer more services/streams.
 
#6 ·
So I wonder how the HD tuner portion of this unit works. Do you still tune into the FM and AM stations as you would normally or do they play through the CD/AUX connection like the IPOD interface and have a seprate Band for it.
 
#7 · (Edited)
The AM/FM analog tuner is still built into the factory stereo and doesn't use an aux feed. You would use it with HD radio like you would without; don't have a Solstice, can't tell you what button to press, but it will be band or source and appear as the standard FM/FM1/FM2 or whatever is normal. The HD radio, though, will be an aux feed and when connected, will appear on the aux list due to its connection to the aux bus. It will show up with an HD-FM or HD-AM tag when cycling through the sources.

EDIT: for clarity, understand that the OEM head unit will send its control signals over the aux bus to the HD tuner. When changing the station, just roll the dial as you would normally while on the HD-FM or HD-AM band.
 
#9 · (Edited)
I decided to go ahead with this. I have XM, but I don't find myself listening to it much. I've only found 2 or 3 stations that I listen to regularly. We have a handful af local stations that I listen to, and a few of them are multicasting other stations on HDradio. I think the ones that will benefit most will be the AM sports stations that don't sound that great. The digital feed of them should sound much better. I listen to local radio when I want to keep up with whats new or local. When I just want to hear what I want to hear, with no comercials, I have CDs or MP3s. The iPOD interface seems to be similar to the PAL unit. The addition of a second input option makes it better in my opinion. I can even plug in the output of my garmin GPS into it instead of plugging it into the front panel of the radio. Although it is limited to two inputs at a time; they said I could use any two. I wonder if a Sirius tuner could be added? I like the channel lineup on Sirius better than XM. I will post more here when I get it up and running.
 
#11 ·
OK, I've had a little road time with this so here's the skinny. This thing is an interface that allows you to break the link between your factory radio and the XM tuner, and put a module in that gives you a HDradio tuner and an iPOD controller.

First for the HD radio part. This thing works by emulating the XM band on your factory radio, so the display shows all of your AM/FM stations with an XM number. At first this can be kind of confusing, but once you realize what's going on, you'll remember what the numbers are. For instance, I listen to 94.7 FM. The radio displays this as XM225. I now have it saved in the preset buttons as XM225. The confusing part is that I have to remember what this preset is for. If I press the info button it will cycle the station name, song title, and artist. On HD radio some stations have multicasting. For instance, 94.7 around here is KSHE. They have KSHE-HD1, KSHE-HD2, and KSHE-HD3. The first one is the same as the analog station, but the other two have different content, and are comercial free. The only quirk about this is that all 3 are under the same XM channel number, and can not be stored separately in the presets. I can save the first one then I have to seek up to the others.
The sound is excellent. When tuning in an FM station, it plays the analog signal for a few secconds until it locks in the digital signal. When it switches over, the difference is amazing. The sound is crisper and fuller, as well as louder. I don't know if the increased volume is from a higher signal or what, but it is also key to one of the downsides of the sound. The digital signal will ocasionally cut out, and the sound level drops significantly. If it cuts out while listening to a multicast station, it goes back to the analog station. This signal dropping gets worse as you get further from the source. The range of the digital signal is not as good as the analog signal. there is no fuzzy fade of the signal. It's either there or it's not. It's just the nature of a digital signal.

Now for the iPOD control. First I must qualify that I am as new to the iPOD as I am to this interface. I bought my iPOD about a week prior to getting the interface. If you are familiar with the iPOD you know how intuitive it is. The interface is fairly easy to use as well, but there is a bit of a learning curve. As with the HD radio, this is also emulating XM, so the buttons used to controll the advanced functions of the iPOD are assigned an XM number and need to be saved in the presets and remembered what they do. For instance button 4 is saved as XM7 and this allows you to enter browse mode, and button 5 is saved as XM8 and cycles through the shuffle options. The buttons are not labled for what they do. they merely have the corresponding XM number above them. This is annoying, but once you remember what each button does, it works pretty good. The communication seems kind of slow between the iPOD and the radio, but from what I have read the PAL unit you can get from GM works very similar. The sound is also excellent.

I did also get an aux input cable that I can use instead of one of the two input sources, but I have not used it yet. I asked about a sirius tuner, but they said none is available for this application yet.

So far, I would have to say that I'm not sure if this was money well spent yet. The sound is great, and the ability to have these two inputs available is nice, but I wish it was more user friendly. This is probably the only way right now to add these two inputs to the factory radio. I am sure that in the future there will be factory radios equipped with these features, but it might be a while. There are probably aftermarket units that offer these features, but I did not want to replace the factory radio, so this was the way to get them.
 
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