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Thread: DAB DAB+ FM Digital Radio Development Board

  1. #181
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    I'm planning to use my board in the car with a Nexus 7, and writing my own app for it. I'm doing this mainly for learning some Android programming with a purpose, so will probably take me a while! :-)

    Quote Originally Posted by redgy View Post
    I've already looked at that and it's one of my backup plans.
    The iVy looks good value, pretty much the same price as the Monkey board but with the bluetooth and the more capable chipset.
    If you want something working straight away I would go for that.
    You could probably mod it to add a external antenna for car use.

  2. #182
    Constant Bitrate
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    I am experiencing some noise issues.
    Noise is being injected into my linein port from dab board. I can confirm it is from dab board because I have turned the system volume on max and dab vol on 1 with noise present. I then muted line in from pc and the noise is completly removed.

    This noise does not increase with volume increase of dab board. It is always there at same level, but when dab volume is increased, the sound of radio station is placed'over the top' of this noise signal. This becomes a big issue when trying to listen to radio at low levels.

    Has anyone here experiences this noise?
    What do you think is a solution?

    I am using stock car aerial (amped) with win7, 32 bit

    thank
    Mos

  3. #183
    Maximum Bitrate Mickz's Avatar
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    Hi mos, itís one of the problems with controlling volume at a device thatís connected via USB. It comes down to a variation of the old earth loop problem.

    If you unplug the module audio output and short the tip to the metal earth shield of the USB cable you will often hear a similar noise (especially if the line input level is wound up high). This is basically what you are doing when you drop the level down to one. It is almost exactly what happens when you press the mute button on the DAB radio. I assume the noise is still there when you do that?

    Depending on how heavy (thick) the audio shield is and how long the cable run you can be anywhere between lots of noise or very little. Thicker earth cable brings the Module earth closer to the line-in ground reference. So the first thing to try is a very heavy double or triple shield audio cable.

    If you canít remove the noise with different earthing and cable then you need to set the signal to noise ratio at an optimum level and you do this by adjusting the output of any USB powered signal source as high as you can without overloading the Line input and then adjust the line input to the loudest desired playback level when the master volume / amp input is set to the loudest position you would run other signal sources at.

    As a last resort you could also try a true USB power signal and earth isolator but good quality units cost and no guarantee it will work on this noise or module.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
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    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  4. #184
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    actally more shielding is WORSE
    what people dont know, sheilding is for HIGH FREQUENCY, the noise you hear is NOT HIGH FREQ
    phone company solved the problem more than 50 years ago! its call TWISTED PAIR
    not to mention, the nosie isnt being radiated into the cables...

    anyway.. USB is a noisy power system, simple solution would be isolation transformwe on the AUDIO, cheap one, prob < $20 on ebay
    like
    http://www.ebay.com/itm/PAC-SNI-1-3-...item43b518db61

    you could also isolate the USB power supply (more expensive, and opens other minor doors)
    -Thanks
    Mitch
    www.rush2112.net

    "Did you test it in carwings??"

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  5. #185
    Maximum Bitrate Mickz's Avatar
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    Audio cable shielding is for low frequent noise – 50Hz and 60Hz mains hum or Linear PSU 100 or 120Hz hum. The reason for using heavy shielded cable is not to stop this digital USB communication noise from getting into the cable but to bring the module earth as closer to the Line input earth, which it will do. Twisted pair is balanced feed in audio systems and if you want to mod the line input and module output then go to a balanced line connection, either transformer or electronically balanced, but it is used more with long audio runs, earth loop rejection and induced noise.

    A quality isolation transformer is a good idea as the high impedance and low power at this stage should cause minimal low frequency loss.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
    8" 16:9 TRANSFLECTIVE, Win8-64, Dual GPS RX and Garmin PC + Odyssey Nav, FM-DAB+, BB-Rec
    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  6. #186
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    Mar 2010
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    What aerial are people using with these monkeyboards?

    My stock FM aerial is useless for DAB and pretty useless for FM (it should really be amped for FM).

  7. #187
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    I'm using mine on the antenna that came with it. Works fine on FM and DAB for me. I'm 27 Miles from Mendip transmitter.
    Unless you mean in a car situation?

  8. #188
    Maximum Bitrate rray's Avatar
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    Does the FM part work for US broadcasts?

    I like the low current part.

    Sent from my SCH-I535 using Tapatalk 2

  9. #189
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    Quote Originally Posted by Dabbler View Post
    I'm using mine on the antenna that came with it. Works fine on FM and DAB for me. I'm 27 Miles from Mendip transmitter.
    Unless you mean in a car situation?
    Yes, I mean in the car.

    The supplied aerial is fine in the house.

    So far, in-car test's have been pretty equal between the monkeyboard (with stock aerial) and Venice 5 (with small piece of wire).

  10. #190
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    Quote Originally Posted by rray View Post
    Does the FM part work for US broadcasts?

    I like the low current part.

    Sent from my SCH-I535 using Tapatalk 2
    As far as I'm aware the US FM Band is 87.8–108MHz and this frequency range is covered by the monkeyboard.

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