Problem with Si4713 Not Transmitting

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andybates
 
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Problem with Si4713 Not Transmitting

Post by andybates »

I've been trying to get my FM+RDS Transmitter (Si4713) working with an Arduino Nano for a project.
It transmits intermittently and after reading through a few forum posts I found this: viewtopic.php?f=22&t=63329&p=320909&hil ... 13#p320909

I'm basically having the same issue as that user, where the transmitter will constantly 'search' for the station but not start transmitting. I followed their advice and added a delay(250); where they specified and ta-da! The transmitter began working.

The only problem is now once it's all set up in my project it's not working again (consistently anyway).

Can anyone offer any help/advice? I would order a replacement part but I need this functional for early next week as it's going into an artwork and I have a gallery opening. And I'm based in Australia.

Thanks :)

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adafruit_support_mike
 
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Re: Problem with Si4713 Not Transmitting

Post by adafruit_support_mike »

This will sound silly, but start at the free end of the antenna and coil it around a pencil or something, shortening the overall length of the antenna about half an inch each time.

The chip starts by doing a scan of the frequency range looking for the one that offers the best signal-to-noise ratio, then scales the transmission power based on what it finds. We've seen cases where the scan seems to hit some kind of resonance with a full length antenna and scales the power to a level that's too low for transmission.

Changing the length of the antenna changes the resonant frequency, and the radio chooses a better power level.

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andybates
 
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Re: Problem with Si4713 Not Transmitting

Post by andybates »

Thanks a lot for the reply! I'll have a try of this soon and let you know how I go.

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andybates
 
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Re: Problem with Si4713 Not Transmitting

Post by andybates »

Hi again,

I've tried coiling the antenna wire around a pencil and have had *some* luck.
Nothing much was changing but as the wire started to get very short the transmission became a little more stable.
It's still not reliable though and I really need this to work 100% as it's part of a performance work which will have quite a crowd (so no room to tinker with things if they break).

Any more suggestions?

In the mean time Im going to remove the current antenna wire and try varied lengths to find the 'sweet spot'.

UPDATE: With a 10cm (3.2 inches approx) antenna wire the transmission is much better but still not stable (keeps dropping in and out, even without moving the antenna)

UPDATE 2: So when I connect my Arduino/transmitter to my computer it starts transmitting perfectly without interference. Then when I connect it to a battery the fluctuating transmission starts happening again. I've tried different voltages (aiming to use a 3.7v LiPo + 5v stepper, also tried a 9v battery) but both produce the same result. I'm really stumped here so any help would be amazing!

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adafruit_support_mike
 
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Re: Problem with Si4713 Not Transmitting

Post by adafruit_support_mike »

If you're using a 9v battery, that's probably your culprit.

9v batteries don't hold much energy (around 500mAh) or deliver much current (around 500mA), and don't make good power sources for Arduino projects. A 4-pack to 6-pack of AA cells will give you much better power (2000mAh @ 2A), and will probably cost less.

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