Questions tagged [modem]

Use this tag whenever the subject includes Modulation and Demodulation of in-channel digital signals.

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9 votes
7 answers
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How does IQ modulation work (intuitively)?

I'm trying to get my head around IQ modulation. What I understand so far is that each of the I and Q branches of the mixer produce two sidebands with the same frequency components, but in the Q branch,...
John B's user avatar
  • 191
3 votes
1 answer
199 views

How do I write a modem for DireWolf?

I was looking at the selection of modem bauds for DireWolf and it seems the highest baud modem is 9600 baud, and I am using a sound card that can reach 48 khz. Is there any way that I can write a ...
Steve Mucci's user avatar
0 votes
2 answers
80 views

What is "allied mode" with regards to PSK31?

Wikipedia says: Colloquial usage of the term 'PSK31' in amateur radio usually implies the use of the most commonly used variant of PSK31: binary phase shift keying (BPSK). BPSK uses no error control, ...
Xunie's user avatar
  • 214
2 votes
2 answers
2k views

Fast TCP/IP radio modem on UHF band

I'm interested if it is possible to have a data radio modem that works on the UHF band 400MHz for TCP/IP communication. What I have in mind is something similar to a router, but using UHF band for ...
Synaps3's user avatar
  • 425
7 votes
3 answers
2k views

Is there a difference between AFSK and FSK for AX.25/APRS USE?

APRS uses the AX.25 protocol which assumes the Bell 202 AFSK modulation scheme to generate the actual radio signal. Is there any reason the same signal can't be generated directly with FSK without ...
jgalak's user avatar
  • 173
1 vote
1 answer
746 views

FSK Rx sensitivity with different deviations

I used an RF generator transmitting FSK packets with a datarate of 50 kbps. The deviation was 12.5 kHz. With this combination of datarate and deviation the modulation index is 0.5. I found that my ...
Mikey's user avatar
  • 113
4 votes
1 answer
2k views

SDR with the Raspberry Pi

I wanted to explore digital modes by connecting a Raspberry Pi via audio cables to a transceiver. However, I realized that thanks to the clock generator, the raspberry pi can produce RF signals ...
Edgar H's user avatar
  • 185