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Thread: HU Quality AM/FM RDS/RBDS Radio with Features

  1. #301
    My Village Called 0l33l's Avatar
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    Quote Originally Posted by rando
    huh? Definitely not true. I think you're confusing behavior of the demo application (definitely not a production ready app) with that of the actual radio performance. Remember, I just hacked that app together last night.

    The seek-scan algorithm (implemented in the code) just looks for stations in .2MHz increments starting at whatever you had entered into the tuning field text box. So if you started with an invalid U.S. tuning frequency (i.e. anything not ending in an odd increment) it would roll all the way around until it got to something greater than 107.9. Then it would jump back to a valid frequency starting at 87.9 and continue seeking; at which point it would find stations again. Sorry, I guess I should have explained that better to avoid this kind of confusion.
    Ok, then I should have said the demo app. I think it did actually get a station above 100, but that was like the second time I clicked seek Its probably just the demo app. I didn't get a chance to try an even frequency... I didn't feel like confusing it

    The hardware and software you saw can and did tune (and correctly seek-stop) on frequencies all over the FM band. 105.9 didn't tune well even when manually entered. That problem is very likely related to the specific antenna performance in my truck. To a lessor extent, it's possible there are settings in the radio hardware that might have made it possible to lock into the station regardless. Also, the assembly technique (point to point wiring, multiple circuit boards, basic inattention to RF signal crossings, etc) may also limit the end performance of the EM.

    I believe the hiss is also related to signal quality because it's not consistent across every station. There are numerous settings in the signal processor that (I think) are designed to compensate for this. I'm not using any of those settings yet. I'll let you know if I discover something about this.
    I'm guessing that 105.9 just didn't tune in well because its a polarized antenna and we didn't have it hooked up on both sides.

    To sum it up: an excellent start

    P.S: What language did you write the demo app in?

  2. #302
    FLAC aoLhaTer's Avatar
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    I can now officially say that I have seen rando's radio thingamajig (name pending) does indeed work and it does work well
    Very impressive work

  3. #303
    Raw Wave rando's Avatar
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    Quote Originally Posted by 0l33l
    What language did you write the demo app in?
    vb.NET 2005 Beta1

  4. #304
    Raw Wave rando's Avatar
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    Quote Originally Posted by rando
    I believe the hiss is also related to signal quality because it's not consistent across every station. There are numerous settings in the signal processor that (I think) are designed to compensate for this. I'm not using any of those settings yet. I'll let you know if I discover something about this.
    OK, We just added a bunch of controls to the CRAM Demo app to adjust some of these other settings. Upon adjusting the FM channel roll-off correction (back to the defaults ), the excessive hiss went away. We also disabled the unused output channels as well as the blending of (currently) unused NAV Input. This too eliminated a bit of noise; a common problem when floating inputs are fed into any audio path.

    There is also a noise detector in the processor designed to detect and filter out unwanted hiss and pops. On top of that, there are 7 high cut filter profiles; 4 of them recommended for FM stereo. So there's going to be lots of dials to make the tweakers happy. Via software, you'll be able to adjust settings that typical radios never give you access to!

    As far as the tuning goes, it's possible to do finer tuning steps than I've been trying. Right now we strictly tune the .2MHz steps that match designated U.S. frequencies. The CRAM Demo app can take advantage of this inside the seek-scan algorithm to (perhaps) improve the tuning performance over what we saw today. The trade-off of using smaller steps is slower seek-scan operation.

  5. #305
    My Village Called 0l33l's Avatar
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    Sweet! The scan seemed to go really fast, so I don't think that people would mind a bit slower scanning. Make the scan frequency adjustable, so the users can choose
    Quote Originally Posted by rando
    OK, I just added a bunch of controls to adjust some of these other settings. Upon adjusting the FM channel roll-off correction (back to the defaults ), the excessive hiss went away. I also disabled the unused output channels as well as the blending of (currently) unused NAV Input. This too eliminated a bit of noise; a common problem when floating inputs are fed into any audio path.

    There is also a noise detector in the processor designed to detect and filter out unwanted hiss and pops. On top of that, there are 7 high cut filter profiles; 4 of them recommended for FM stereo. So there's going to be lots of dials to make the tweakers happy. Via software, you'll be able to adjust settings that typical radios never give you access to!

    As far as the tuning goes, it's possible to do finer tuning steps than I've been trying. Right now I strictly tune the .2MHz steps that match designated U.S. frequencies. I can take advantage of this inside the seek-scan algorithm to (perhaps) improve the tuning performance over what we saw today. The trade-off of using smaller steps is slower seek-scan operation.

  6. #306
    Raw Wave rando's Avatar
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    Quote Originally Posted by 0l33l
    Sweet! The scan seemed to go really fast, so I don't think that people would mind a bit slower scanning. Make the scan frequency adjustable, so the users can choose
    After playing with this a bit, we don't think it's useful. There are ZERO good sounding signals off the designated center frequencies. We're fairly sure what we observed was related to the antenna performance and the exact spot where my truck was parked.

    Regardless, the CRAM Demo software is exactly that; just for demonstration and testing. It will be made available along with a SDK to allow developers to integrate the radio into their front-ends. The SDK will provide a function to tune the radio to any frequency supported by the hardware. A second function (or set of functions) can do range and value checking to support easier implementation in specific localities.

  7. #307
    Maximum Bitrate Seth's Avatar
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    We're slowly getting there guys. We're figuring out many oddities actual HU designers face step by step. Also the signal processor has so many parameters to play with it makes your head spin .
    Even though we are familiar with RF theory most of the fine tuning is done through trial and error (playing with settings) so it will take a while to find the sweet spot .

    Now we all know it works, it can only get better and better from now on

  8. #308
    Constant Bitrate BeaverWise's Avatar
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    Good news, good news... Let us know when it will be hitting store shelves near us.

    (all joking aside, fantastic work guys)
    VIA MII 10000 - 512MB Ram - Dual 2.5" drives, Xenarc 700TSV, Panasonic CW-8132-B, Opus 150, Audigy 2 NX, PowerMate, IOADR1610 10 Relay card

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  10. #310
    Variable Bitrate kmcniece's Avatar
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    I have to admit I was impressed. After talking with Rando about the project and how the system works, I think I have a pretty good understanding of the processes and difficulty involved in making this work cleanly.

    The very fact that you are getting a signal, controlling it all with a quick and dirty frontend and writing your code to make it happen.....welll, that's impressive.

    Nice work, I can't wait to see more...
    EPIA M10000, 512 Ram, Opus 90, GPS, XM, 7" Xenarc, Pioneer HU
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