Alan Campbell
  • Member for 7 years, 2 months
  • Last seen this week
  • Adelaide, Australia
5 answers
19 votes
9k views
SDR: Quadrature demodulation vs direct RF sampling
3 votes

One of the earlier SDR models, the HPSDR, had/has a single receive board: the "Mercury". It used a single high-speed ADC. Details are here. Once the RF is sampled and fed into an FPGA, it typically ...

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2 answers
4 votes
3k views
How to hook up my computer's audio output to my CB Radio?
Accepted answer
3 votes

Most connector plugs make contact at 3 points: 1 Tip (pointy bit), 2 Sleeve (opposite the tip), and 3 Ring (between tip and sleeve). Depending on the rig, two of these will carry audio. One of the ...

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3 answers
9 votes
4k views
What are the I and Q in quadrature sampling?
1 votes

I and Q are somewhat confusing to me, too. I came up with a mental picture, which may help... Consider a piston, in a motor. If you took a flash photo, and the piston was all the way up (or down) it's ...

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4 answers
10 votes
600 views
Why are commercial SDRs so limited in operating frequency?
1 votes

What I've found is: a lot of the SDR designs are sending data. A fair amount of it, too. The bandwidth of a signal increases when it sends more / faster information, and the bandwidth of HF signals is ...

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2 answers
7 votes
363 views
Center frequency spike on software radio for mismatched/disconnected antenna
0 votes

The fact that the spike is present, with no antenna connected, inducates it is a product of the receiver chain. Since it happens bang on the frequency you have tuned, implies the DC or low frequency ...

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2 answers
3 votes
1k views
2m Homebrew Receiver - Chip for frequency
-1 votes

Try a Google search for "2m receiver chip" or "receiver chip 144MHz". Then refine your search to Images - you should see thumbnail pictures of schematics. After that, it's a matter of browsing for a ...

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