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24

According to this the required pin(s) on the BCM43438 were not easy to route out, and so are not connected on the chip.


19

Yes, it can be done, but beware of violating FCC. Details here: External antenna modifications for the Raspberry Pi 3


12

I have seen some tutorial where someone used an Phillips TEA 5767 FM Tuner to receive radio. with this breakout board. You should be successfull with that! It seems the TEA cost about $3~4$. This blog gives a detailed description how you can convert your PI into an FM Tuner: Here in this post where there is a discussion about the PI and the TEA. I hope ...


7

You may be able to get pretty close. My idea goes something like: sync time across all RPi's using NTP broadcast a network message to shoot in the future a listener calculates how long to wait and then performs the action Using NTP you can get all RPi's to be in pretty good time sync with each other. From this Wikipedia article NTP can have sub-1ms ...


5

Forget about the DAC. You need an USB RTL-SDR dongle. They run from $10 - $30 on Amazon. FM radio is the one case where the antenna that they come with is good enough. Install rtl_fm, and then pipe the output of rtl_fm into your Icecast source program.


5

Welcome to the Raspberry Pi SE site! Your question may be judged as off-topic for this site (not saying it will, but it may be), but personally, I'm happy that you've asked it. I say that only because radio applications for the RPi don't seem to get a lot of coverage here - which suggests to me that folks are missing out on one of the best application areas ...


4

If we approximate that the dirty square wave coming from the GPIO pin, is a sinewave, and at the same time assume the antenna is directly driven. Well, then as @joan said. The GPIO maximum current draw is 16 mA. So the formula can be approximated to be: Pavg = Vrms * Imax = (Vpp/Sqrt[2]) * Imax = 3.3 * 0.707 * 0.016 = 0.037 W = 37 mW But at the end of the ...


4

In terms of remote control, you've got a few options. You could SSH into the Pi and control it via the command line. You could install VNC on the Pi and then use a client on another computer to connect to it that way. Alternatively, you could use a bluetooth dongle and pair up a Wii remote, PS3 controller or anything else that uses the bluetooth protocol. ...


4

"How much it is radiating in the RF spectrum?" is a question that's easy to ask, but not to answer - at least not specifically. And if you did have the specific answers, they will only have meaning if you were familiar with the testing standards, or knew the susceptibility of all the items in your environment. Perhaps one way to answer your question is to ...


3

There are two mostly unrelated issues. One is FCC certification as discussed above, the other is WiFi certification. FCC certification is concerned with radiated RF energy across broad spectrums, mostly to protect other consumer electronic equipment like TV's radios, etc, from unwanted interference. FCC certification is required for devices sold in ...


3

There may be radio frequency bands in your country where very low power unlicensed radio emissions might be permitted (FCC Part 15 rules in the U.S.). However an unfiltered GPIO output won't broadcast in only one RF band. The GPIO transmitter trick uses a periodic digital output to produce a radio signal. This is due to one of Fourier's theorems which ...


3

What you need to look at is the IEEE_802.15.4 standard specification. That include many popular protocols for the frequency you are interested in, such as: ZigBee, ISA100.11a, WirelessHART, MiWi, SNAP, and Thread. That frequency belong to the Unlicensed ISM/SRD bands: 863.0 – 870.0 MHz (ETSI EN 300 220). So there are tons of devices Arduino, RPi etc ...


3

You do not need additional resistors/capacitors on the bread board. All the components shown in the linked schematics are already included on the printed circuit board you've got from Adafruit. VDD/GND is connected to the supply voltage. Connect only voltages within the given limits and of correct polarity! Starting at the top of the left side, there are ...


3

The answer is "not very much". I purchased a "TriField" EMF Meter Model TF2 out of general curiosity. Near the floor of my ground-floor room, the RF background reads 0.02 mW/m^2. I could detect RF radiation from a Raspberry Pi 3B+ about 3 inches from the plastic case, beyond that it was indistinguishable from background. For comparison, an Ethernet cable ...


3

First of all: Yes, it is possible that your device is not sending at 433MHz, since other frequencies are written on it. Different countries have different regulations on different frequencies, so there are devices which could send on different frequencies. There are several possible problems here. 433MHz is not a single frequency, it is a frequency band ...


3

You need to ensure only one device is transmitting at a time. You have not shown how you plan to achieve that. Here is some code to test your set up. It is based on my pigpio library and requires the pigpio daemon to be running (sudo pigpiod). It also requires my Virtual Wire module to be in your working directory. http://abyz.me.uk/rpi/pigpio/examples....


3

These types of radio systems are inherently unreliable, which is the reason the transmitter tends to repeat the signal multiple times. Ten repetitions is not unusual. As an aside consider a TV infrared remote control, it will continually transmit the signal until you take your finger off the button. The receiver is seeing radio static. The automatic ...


2

Given that the maximum 3V3 output of the Pi is claimed to be 50 mA that puts an upper limit of 3.3*50 = 165 mW. Furthermore given that an individual gpio is said be harmed if you source or sink more than 16 mA that suggests an upper limit of 52.8 mW. In practice I expect it's much less but have no idea how it could be measured.


2

The noise is probably caused by a 1 second interrupt on the Pi. If you used an Arduino, without the complex multitasking it may not be a problem. It is VERY difficult to separate low level audio from the other circuitry. The conventional solution would be to use an isolating transformer. As the device is unlikely to have a wide bandwidth this wouldn't be ...


2

while recognizing this as a funny and great hack, i'd advise against using it for anything except the proof of concept demo, because broadcasting on unlicensed frequencies might break the law and/or result in legal problems and/or heavy penalties. please, use only licensed equipment to broadcast within the permitted frequency ranges and output power limits. ...


2

the time difference [...] should be as minimal as possible (preferrably under 1 millisecond) That's not very feasible on a single pi sans networking, by which I mean, if you write a program to take a series of photographs spaced with millisecond granularity -- #1 at N, #2 at N + 1014 ms, #3 at N + 5135 ms, etc. -- this timing will fail badly. You might be ...


2

I think you are mixing up signal moldulations. HM-T433 uses FSK (Fequency Shift Keying). Most applications in 443MHz use ASK (Amplitude Shift Keying) and of those most use OOK (On/Off Keying). That means they either send a signal with constant amplitude and frequency for "1" and don't send anything at all for 0. RTL2832 is capable of doing both FSK and ...


2

You will to need to measure the voltage yourself. No one can guarantee the modules you receive will be as illustrated or the same as theirs. If you power the receiver from 5V or more it is safest to use a voltage divider between data out and the receive GPIO. The transmitter side is irrelevant. The data in pin on the module is an input from the Pi, not ...


2

Perhaps there is just too much radio noise. Try my implementation at http://abyz.me.uk/rpi/pigpio/examples.html#pdif2__433D It should use a lot less CPU. It requires pigpio which may already be installed if you are using a recent Raspbian.


2

The product description reads (among its other specs): Line out stereo jack. So it outputs Line Level signals which are supposed to transmit analog audio signals between components and not to drive speakers. Connecting passive speakers (no integrated amp) at their low impedance (4 to 8 Ω) is not recommended. Their load is significantly lower (almost a short ...


2

You might also consider a Software Defined Radio (SDR). The hardware is usually a cheap USB device which plugs into a computer or Raspberry Pi. You can find a tutorial for how to use it with a Raspberry Pi by googling "Raspberry Pi RTL-SDR Scanner" but that is outside the scope of the question.


2

I am also a radio amateur and have noticed broadband interference from a Pi3B. In my case it appears in my Flex 6600 waterfall as closely spaced horizontal lines at the top and bottom of the 40M band. Other bands may also be affected, but the noise is less pronounced. If I disconnect the HDMI cable thing are marginally better, but if I put 3 turns of the ...


2

If you want to have a two-way communication, buy transceiver modules: you'll only need two of them while with separate TX and RX modules you will need 4. Moreover, transceivers are designed to cope with interference, while in your case you run two TX modules on the same frequency, so you can be sure to have interference issues: when you increase the distance,...


1

It sounds a bit strange that RPi Foundation is concerned about breaking FCC certification by documenting the UFL connector site on their board. There are many SBCs which have a UFL connector onboard by design, e.g. Banana Pi M2+: The presence of this connector didn't prevent this BPi from getting its FCC certification. As an owner of a BPi (not this model ...


1

This isn't truly an answer (because there is a lot of variability), just some hints for getting started This SHOULD be possible. But is highly dependent on your hardware. You have to determine what kind of motors the car uses. My guess is some DC motor for propulsion and if it has proportional steering a servo. (Cheap cars might use some kind of DC motor ...


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