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22 votes

What could this signal at 119.9 MHz be?

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 ...
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  • 7,101
8 votes
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What RF attentuator would be used for the HackRF?

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 ...
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6 votes

Software Defined Radio hardware

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 ...
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  • 140k
5 votes

What RF attentuator would be used for the HackRF?

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 ...
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  • 2,175
5 votes

Determine the working frequency band of unknown RFID chip

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 ...
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  • 979
5 votes

How would I go about analyzing this SDR-captured 300 MHz radio signal?

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 ...
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  • 1,032
5 votes

High precision distance between two GPS devices (may be GNSS-SDR)

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 ...
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  • 6,792
4 votes

How would I go about analyzing this SDR-captured 300 MHz radio signal?

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 ...
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4 votes

Where does SDR IQ data come from?

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 ...
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4 votes

DSP on the Raspberry Pi

So, first of all, I'm biased. I maintain the GNU Radio source code. So, what you want to do is pretty much perfectly fulfilled by GNU Radio For flexible connection of signal processing steps, you'd ...
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3 votes

Software Defined Radio hardware

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 ...
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3 votes
Accepted

Where does SDR IQ data come from?

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 ...
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3 votes
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Software Defined Radio hardware

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 ...
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  • 12.2k
3 votes
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Bandwidth vs sample rate in SDR

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 ...
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  • 164k
3 votes
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Can I transmit in the ISM band without a ham radio license?

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....
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  • 78.8k
3 votes
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SDR pcb design guide

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 ...
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  • 21.4k
3 votes

Replacing 28.8Mhz TCO with up-converted GPSDO 10Mhz signal?

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 . ...
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3 votes

Homemade GPS Receiver: Cascading LNAs and Band-Pass Filters?

I've connected my RTL-SDR Blog stick to a GPS antenna, and when the LNA bias is on, I see a modest increase in the noise, over the band 1565-1585 MHz. (I used some kind of scanning software, the ...
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  • 7,138
3 votes

IQ modulation and phasors: which first?

The fundamental motivation is: "Arbitrary AM modulation and adding two sine waves together is easy, arbitrary phase modulation is hard." Here's the details. When we send information on a ...
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  • 1,871
3 votes

Can software defined radio be used as noise generator?

Could I achieve this with a software defined radio? You can produce any band-limited signal, given its bandwidth is within the capabilities of the SDR. So, yes. You'll find that "shortwave ...
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3 votes

Getting started with Radio design

You'd not start by buying hardware – you'd start by understanding how these devices work, then implementing them in software, then making your software fast enough to run in realtime, then you ...
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2 votes
Accepted

Antenna for broadcast AM reception on ARM Radio SDR

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 ~...
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2 votes

Designing an optimal BPSK and/or QPSK transciever in SDR

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 ...
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  • 1,796
2 votes

"56k modem" found in VHF band

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 ...
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  • 15.7k
2 votes

Antenna preamplifier

The Q2n2222 is a 2N2222 clone. It's ancient. It was marketed as a switching transistor, the datasheets you can still find for this type of transistor usually don't even specify frequency-dependent ...
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2 votes

How can I measure my smartphone transmitted power?

How can I measure my smartphone transmitted power? You can't. At least not in a very meaningful way. I mean, using an SDR receiver you can get an indication of the frequency your phone is using and ...
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  • 78.8k
2 votes
Accepted

Is it possible to replicate a Novotron 522 remote control?

Unless there is an unexpected flaw in their design, it is not possible. Rolling codes are designed so that, even if you can intercept the data frame that has been transmitted from the genuine remote, ...
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  • 15.5k
2 votes

Determining motor position with EMI

Think about it for a moment. Even if you know exactly how many steps the motor makes during each movement, there's no way to determine the direction of the movement from the EMI emissions. Therefore, ...
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  • 164k
2 votes
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How do Software Defined Radios have such big bandwidth?

can scan it's whole frequency range (1MHz to 6GHz) in the same time. How does that happen? Not at all. The HackRF (and other SDRs) can just be tuned to arbitrary frequencies, giving you arbitrary ...
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2 votes

What sampling rate is needed for demodulating and decoding GPS signal data?

A more detailed understanding of the Nyquist rate would show that it requires sampling at twice the information bandwidth, not the carrier frequency. In the GPS case, there is no information at the ...
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  • 12.5k

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