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7 votes

Output power from the TX/RX port of the USRP N210 decreases as the frequency increases

That's an expected phenomenon: Real-world physical systems tend to be frequency-selective (i.e. not constant over frequency), and "at large scale" low-pass systems. This applies to ...
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6 votes

GnuRadio RF transmission, legal and safety issues

The frequency allocation chart is really more artistic than informative. You can not and should not use that as a guide for selecting a frequency. There is too much information to fit on the chart, ...
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5 votes
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Advantages of IQ generation at Mixer Stage or within FPGA for SDRs

Well, the need for one ADC that's twice as fast is definitely a very important factor! The same "it gets harder with rising frequency" argument applies to the anti-aliasing filter: Building a low-...
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5 votes
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How can I make WBFM receiver without using WBFM Receive block?

General principle: In GNU Radio you cannot ever have a flow graph with a loop in it. If you wish to have feedback of some kind, it must be implemented in a single block. (There are many existing ...
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4 votes
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Ettus B210 USRP Is it possible to transmit on both Tx Ports either with same or different application?

UHD requires a USRP to be owned by one process only, so no, you can't share the same USRP across two flow graphs, but you could use for example the ZeroMQ PUB/SUB sink/source pair to stream data in ...
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4 votes

GNU Radio - Frequency parameter of Signal Source Block

For a complex-valued sampled stream, the sample rate must be greater than twice the signal represented. The sample rate in your graph is set to 384k, so it's not possible to represent a 98400 kHz ...
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4 votes

What cause the spectrum peak of `center frequency`?

In addition to the clock leakage mentioned in the other answer, a DC offset spike can also show up in the downmixed IQ if the mixer(s) and/or the ADC(s) aren’t perfectly balanced (exactly equal gains ...
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4 votes
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What cause the spectrum peak of `center frequency`?

Internal interference in the radio. There's a clock ticking at that frequency in order to downmix the signal, and spurious emissions from that clock is being picked up by other circuitry. The clock is ...
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3 votes

FMCW radar with USRP and GNU Radio Companion

You've got a few very concerning conceptual and technical problems there, many of which will be adressed by the console output, which you should probably read! You can only sweep within your nyquist ...
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3 votes
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USRP Safe Gain Values

I have connected the TX/RX port of one radio to the RX2 port of the other with an RF cable as a simulated radio link. DO NOT DO THAT. Always, always, always, in any case, under all circumstances, ...
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3 votes

Advantages of IQ generation at Mixer Stage or within FPGA for SDRs

I would like to add a bit of my intelligence to this topic as I did some extra reading. This answer isn't a stand alone answer but merely a minute extension to the answer posted by Marcus Muller. I ...
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  • 682
3 votes

How exactly does Data Whitening improve performance?

Imagine your data is not white. That means that at certain periods, it contains more variance, and hence information, than on others. That's bad, because now certain frequencies become more ...
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3 votes
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What can be used to protect an SDR receiver against bursts?

There are a few types of overload you might be suffering from. Here are some possible solutions: 1. An in-band signal, stronger than your wanted signal This may drive the AGC and make the wanted ...
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  • 8,225
2 votes

Viewing the broadcast FM spectrum using a USRP N210

I don't see anything wrong with your basic GNU Radio flow graph, so it is likely a hardware configuration issue. I'm not familiar with the USRP N210 in particular, so this is a bit generic: In my ...
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2 votes
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Choose the right dongle for NOAA images visualization with GnuRadio

Picking up NOAA imagery is mostly a feat of constructing a good antenna than having a high bandwidth, or great clock. Thus, for reception only, build a nice helical antenna, and any cheap RTL Dongle, ...
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2 votes
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How high an SWR can the USRP 2901 (B210) handle?

The B210 / NI-USRP 2901 has no problems with an open end condition or a short: You can't damage the transmitter with its own power. There's no significant PA on that board. So, it can handle any ...
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2 votes

USRP Safe Gain Values

According to the Ettus Research Knowledge Base: The maximum input power for the B200/B210/B200mini/B205mini is 0 dBm. and Power Output >10dBm 10 dBm to 0 dBm is a difference of 10 dB, so an ...
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2 votes

Most accurate way to measure signal power with (cheap) Spectrum Analyzer

However, depending on which options I choose on the Spectrum Analyzer, my measurements are different by up to 6-10 dB(!). Using a spectrum analyzer needs a bit of understanding what it does: it ...
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2 votes
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How to record and replay the `center frequency` when `file_sink`?

Not at all. The file sink, as any sample-processing block in GNU Radio, is not aware of RF properties – all it sees are the baseband samples. So, the representation of things being centered around 0 ...
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2 votes
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Does GPS port of USRP B210 only used for GPSDO?

Does GPS port of USRP B210 only used for GPSDO? Yes. You can actually follow the RF trace on the board if you have it in front of you. Also, Ettus has their schematics online and you can see the ...
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2 votes
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Does signal frequency affect the band width of SDR hardware?

In SDR receivers which use a mixer in front of the ADC to receive radio spectrum above the ADC sample rate(s), the sample rates and down-conversion frequency are usually independent settable (except ...
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  • 12.5k
2 votes

What can be used to protect an SDR receiver against bursts?

If your SDR has over 100 dB of dynamic range, I would attenuate the input path (and all parasitic paths!) down to where the average power is 10 dB above the MDS (minimum detectable level) of the SDR. ...
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  • 12.5k
1 vote

What can be used to protect an SDR receiver against bursts?

Your receiver should be inside an enclosure for shielding, if it isn't already. A common trick to prevent damage to a receiver from nearby transmitters is to put back-to-back diodes in the received ...
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  • 8,922
1 vote

What cause the shape of frequency spectrum convex or concave?

The edges of your spectrum is where the performance of the receiver is hitting the limit. there is a trade-off between flatness and total bandwidth. they could have made the bandwidth smaller to keep ...
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  • 373
1 vote
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What cause the shape of frequency spectrum convex or concave?

Answer to part 2: The USRP SDR uses an downconverting IQ modulator before the ADCs. An error in quadrature phase or quadrature levels of the two IQ modulator clock signals or gain and delay balance ...
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  • 12.5k
1 vote

Upconvert Signal with USRP N210 in GNU Radio Companion

500 kHz = 0.5 MHz = 0.0005 GHz. You're providing a signal at +500 kHz, and then upconverting it to produce a signal at 2.5005 GHz. Are you sure that your measurement of the output frequency (and the ...
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  • 23.1k
1 vote
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Receiving different gain values on two RX channels on Ettus USRP B210

The difference was caused by the splitter I was using to send the signal to both channels.
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1 vote

GnuRadio RF transmission, legal and safety issues

The safest way to run a transmit / receive application is using a loopback cable. Just remember to include an attenuator in your path so that the receiver doesn't get damaged.
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