Radio transmission from Pyra


ò.Ó said:
https://osmocom.org/projects/osmo-fl2k/wiki
looks like it only works with USB 3 though, hmmm..,.
Click to expand...
If you scroll down past the pictures to the bottom of the first table, you can see that they tested hooking it up to a USB2 host. A USB3 host is not required, although I don't know if you'd be able to transmit decent FM at only 14MSps. I make the nyquist rate of a 90MHz FM signal to be 180MSps, so I guess we're looking at medium wave there at best really.
 
I wonder if the PiTx can be ported though, that does AM. I prefer that in cars, stereo sounds weird in cars to me. I'll have a look though!
 
No, you'd need towards the cheapest end to plug in a usb->vga adaptor and VGA cable. If there's a spare gpio or something, you might be able to attach a simple wire to that, but I'm not sure what sort of dipole length you need offhand for FM, and fitting that inside the case might be tricky.
 
Ah i see..okay than its more Easy to use an external FM Transmitter when i need that.
....or Bluetooth :)

But a nice Idea.
Thank you for explaining that.
 
It might not even need an antenna if it's close enough to the radio! I know the one on the RPi doesn't need an antenna.
 
You don't want to do this anyway, at least not without a lowpass filter on your antenna. It's a neat demo, but because you're modulating a square wave (pin on/off) it vomits harmonics all over the spectrum. If the power is large enough to be practically useful in the frequency you want, it's also large enough to cause a huge amount of noise in every odd multiple of that frequency.

For the same reason, AM (amplitude modulation) is impossible without further circuitry. You can't generate a sine wave carrier signal, or modulate the amplitude of the wave you do generate. You could possibly do it with a lowpass filter again, by using PWM to approximate the analog signal (the same trick used to do things like make disk drive stepper motors play music - in this case the ear acts as the lowpass filter).
 
Well ideally, I'd like something I can plug into the USB port and drape the wire across the dashboard of the car, near the antenna. But I just got one of those bluetooth FM repeater thingies. But this would still be neat to be able to play music from the Pyra on any radio. I might have to build something I can plug into it. With a filter, of course.
 
Unfortunately that's a bit big, and their site is broken so there doesn't appear to be a way to buy one, or even see how much it costs.
 
Silent-Hunter said:
Unfortunately that's a bit big, and their site is broken so there doesn't appear to be a way to buy one, or even see how much it costs.
Click to expand...

I'm under the assumption that for some reason you would rather have a device that plugs into a Pyra then transmits FM to the radio instead of just using a Bluetooth - FM re-transmitter.

How about this one that skips the USB and goes straight out of the headphone jack?
Code: 
https://www.amazon.com/JETech-Wireless-Transmitter-Phones-Charger/dp/B01HXQYDH4
 
Well if it's going to plug into the car, I'd rather it be bluetooth. What I'm looking for is something that lets me basically use radios as speakers. So if I'm over at my aunt's for example I can play music from her radio without plugging anything into it. I gave up on the car thing already, and bought an FM thing.
 
dTal said:
For the same reason, AM (amplitude modulation) is impossible without further circuitry. You can't generate a sine wave carrier signal, or modulate the amplitude of the wave you do generate. You could possibly do it with a lowpass filter again, by using PWM to approximate the analog signal (the same trick used to do things like make disk drive stepper motors play music - in this case the ear acts as the lowpass filter).
Click to expand...


Eh what? I thought the heads were moving at the same frequency as whatever was in the source signal they were playing.
[doublepost=1551413052,1551412842][/doublepost]
Grench said:
I'm under the assumption that for some reason you would rather have a device that plugs into a Pyra then transmits FM to the radio instead of just using a Bluetooth - FM re-transmitter.

How about this one that skips the USB and goes straight out of the headphone jack?
Code: 
https://www.amazon.com/JETech-Wireless-Transmitter-Phones-Charger/dp/B01HXQYDH4
Click to expand...

Quite sensible imo.
 
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