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22

This signal is an extremely inefficient use of bandwidth, as you can see because there is an essentially unused area between the center and ±125 kHz. Therefore, I expect that it is almost certainly unintentional radiation (a.k.a. RFI/EMI) rather than a meaningful transmission. The origin of the signal could be as follows — there are other ways it could ...


14

The second technique you mention is the way to do it, using what is called a "Software Defined Radio" or SDR. Many radio amateurs are using SDRs, and the simple ones are very cheap, about 30 dollars for a kit that down-converts the input into in-phase and quadrature baseband audio output which is fed into the stereo inputs of a PC sound card for digital ...


9

Practically, information is not lost in a properly designed down-conversion process, but that's because the RF signal is rarely used in the way you suggest (and when it is, you wouldn't down-convert it). Take the process you described : adding information to a 400MHz carrier - this process is called modulation. Simply turning the carrier on or off for an ...


7

The thing to realize here is that if you take a sinusoidal carrier and switch it on and off, change its amplitude, frequency, or modulate it in any way, then it can be shown mathematically, but somewhat counter-intuitively, that what you are doing is introducing sinusoidal components at other frequencies. In fact, any periodic waveform can be represented as ...


6

Attenuation will reduce overall signal level without changing the receiver noise floor, preventing the reception of very small signals. Generally you do not need one unless you are connecting the input directly to the output of an RF source with no antenna, or your antenna is very close to a powerful transmitter antenna. -5 dBm is very 'hot', generally you'...


6

Data rate => bandwidth. USB will handle only a limited data rate, and the entire digitised bandwidth would have to fit into this channel. With an FPGA at the remote end, it can crunch the digitised bandwidth down to the actual channel bandwidth, which could be one or two orders of magnitude smaller, and send that down the USB. It could go further and ...


5

Actually, RTL-SDR can solve this in ... several 20 USD dongles, each covering up to 3 MHz of FM spectrum (I achieved clear reception of 4 or 5 FM stations with 0.4 MHz spacing per dongle). As was found by osmocomSDR project, there are lot of Chinese DVB-T USB receivers, built on Realtek RTL2832U chip and some 50MHz - 1+ GHz I/Q radio frontend. This chip ...


4

Many tags use 125KHz and 13.56MHz. Your likley in these 2 bands. Other UHF and 2.4GHz If your is a passive tag (most low cost tags, designed to work within a few inches, are passive), for sure and definite answer, I have used Radio Frequency spectrum analyzer with tracking signal generator and 1 to 2 inch diameter, self make loop antenna, Scan freq range ...


4

For your first solution you shouldnt need a sound card. They make usb fm receivers. Like this: http://www.amazon.com/ADS-RDX-155-EF-Instant-FM-Music/dp/B000HNHA12/ref=pd_sim_sbs_e1 Buying tens of these for $200 will be cheaper (and far faster) than a custom solution using the aforementioned SDR (software defined radio). Though if your goal is a fun ...


4

An RF attenuator have 3 important parameters: maximum input power (usually expressed in W, but might also be in dBW or dBm), attenuation (expressed in dB) and frequency range. For example you might have a 20 dB, 2 W, DC-8 GHz attenuator.This attenuator would accept a maximum of 2 W (33 dBm) and would then deliver an output of 13 dBm (33-20). HackRF has a ...


4

Good work getting a sample into audacity for visual inspection. If I understand correctly, your screenshot shows the raw waveform without demodulation (as opposed to baseband audio after FM/AM/USB/etc demodulation). Some folks mentioned PSK and FM modulations which are similar, so you could try setting your demodulator to FM and capturing a new "baseband" ...


4

The "imaginary" part needs to be captured on the analog side, with a separate mixer that uses a LO source that is exactly 90 degrees offset from the "real" LO. In the physical world, only real-valued signals can be transmitted, so on your antenna input you have a real-valued time-continuous signal. If you mix (i.e. multiply) this with your LO signal, the ...


4

How to get 1 cm relative accuracy with GPS: Buy a 1 cm accurate GPS receiver. For that level of accuracy you need an RTK (Real Time Kinematic) receiver. A good system will give you 1 cm accuracies without any averaging. It will also give you a very large bill to pay, those systems aren't cheap. Best bang for you buck would probably be something like the ...


3

Yes, that is totally legal Worldwide, no license needed. Do you own/use a: WiFi access point WiFi on a phone or laptop Microwave oven Bluetooth on a phone or laptop These all operate in the 2.4 - 2.5 GHz ISM band which is legal as long as the device transmits less than (I think, correct me if I'm wrong please) 20 dBm = 10 mW So in your case: no worries, ...


3

35 dBmV means "35 decibels stronger than 1 mV", or about 10^(35/20) = 56 mV RMS. 56 mV is a pretty small signal, so it's unlikely to damage any input that wouldn't be completely destroyed by the ESD of casual handling. There is still the possibility (though unlikely) that the input signal may be too strong for the receiver and would cause clipping. This may ...


3

No, the RTL2832u will not be damaged by the cable signal. After all, that's the application it was originally designed for! You'll probably have to reduce the gain settings in your SDR software to get useful results, though.


3

Look into GNU radio. Here's their hardware page to start.


3

I would recommend using a PLL chip that is capable of generating a 28.8 MHz output and can do so with a 10 MHz input. Take a look at http://www.analog.com/en/products/clock-and-timing/plls.html . The ADF4360 could be a good choice.


3

If you intend to use this transceiver with high data rates then the interface between this and the Zynq should follow high speed routing guidelines for power and ground. I note that there is some guidance in the datasheet on power and ground, but it is not extensive. If you intend to have an external antenna, that will make things a bit simpler, although ...


3

Note: we're going to oversimplify SDR hardware for illustration in this answer ADC --> PC is (one of) the functions of the FPGA The FPGA serves different functions in different SDR designs, but one of its primary purposes is to "just connect the ADC to the PC". I think you don't fully appreciate the process of moving data through the Universal Serial Bus (...


3

Yes, it's possible, this is what the DVB receivers do. You could also do an USB 3.0 design, e.g. based on the EZ-USB FX3, these can be connected to ADCs and DACs easily, and the firmware just sets up a pipe between a bulk endpoint and the peripherals. The downside of this is that the data is completely unprocessed then. You need at least DC offset ...


3

Short answer: The transmitter encoder/modulator e.g. QAM IQ modulation is used everywhere including SDR. Understand some roots in phone data modems since above 1200 baud then up to 56kbps/64kbps then cable and DSK modems , Analog and digital phones , Analog TV since colour was broadcast and now digital TV and fast forward later to SDR's. IQ ...


2

First thing you need to recognize is that designing with a 16-bit ADC is not trivial. Even at 1 sample/s, you need to pay extreme attention to every aspect of the design to achieve 16-bit precision, or even more difficultly, 16-bit accuracy. At 130 MSa/s, everything is even more difficult. The parts you need to do this kind of design simply won't be ...


2

They are related, but not directly. The sample rate must be at least 2× the bandwidth in order to satisfy the Niquist criterion with respect to aliasing. However, since "real world" filters are not ideal brick-wall filters, you need to allow a higher margin on the sample rate — or accept a lower usable bandwidth. Some texts might use "sample ...


2

For a project of mine(uhf radios, pic32mx450f), I went with bpsk and 8b/10b encoding, with a 10 sine + 8b/10b k_28_1 preamble. This allows syncing to the correct phase, and then I run the moving bitstream through the detector until it hits the special code. For phase detection, I looked at quite a few different ways, but ended up doing simple peak ...


2

The AD9862 has an input impedance of 200 ohms typical and that is of some interest but not of major importance when it comes to the outside world interfacing. Generally speaking, a chip input impedance of infinity is easier to work with - in this way it can be ignored providing the chip doesn't sit more than a few inches away from the resistor/components ...


2

What PC DSP chip are you referring to? I don't know of any DSP chip inside of commercial PCs that's capable of performing software defined radio. It is possible to do the necessary processing for a baseband bandwidth of a handful of MHz with the CPU, but there is no getting around the need for an analog front end. A device the the USRP has a decent FPGA ...


2

Can anyone help me understand how I can get the key from this signal or any other tips on deciphering? Well, since you have access to the transmitter, play around with it! What does the signal look like if the code is set to all-0, when individual switches are on 1, when you have two switches at 1 and so forth. Then, from the signal's shape it's a bit ...


2

Ok, doing a little work with the calculators found here and here, I came up with an idea that I think you might like. Materials: 14ga-18ga "fray wire" 9" section of 4" PVC pipe Power drill with ~1" hole saw & 1/4" bits 3/4" pvc pipe (at least a foot) 3/4" & 4" PVC pipe end-caps 1+ zip tie(s) Magnet wire (about 150') Some BBs, iron ...


2

160MHz lies in the Marine VHF Radio Band. I guess the signal you received is for the marine vessel tracking system called AIS (Automatic identification system). In section Technical Specification of the Wikipedia Article you find that it uses 2 channels at 161.975MHz and 162.025MHz and carries a 1200baud digital signal which fits to the details you ...


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