Архив за 17.02.2018

sdr trunking

So I'm trying to trunk a Motorola type II smart zone. I've got uni trucker working and its registering all the conversations but when i try to play sound on dsd+ no sound comes out. IM new to this I've followed the step by steps. on the event log for dsd+ it just comes up 50 lockouts cleared.

submitted by /u/bobbyfrankfrank
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I want to thank everyone who helped me with my planar disc antenna not working

It was the coax I was using, It was from an old wifi antenna rig, and I don't think it was meant for the frequencies I was trying to use it for.

Switched to some standard RG6 tv coax, and its working fantastic now. Listening to my local police dispatch now.

submitted by /u/MediocreFisherman
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Anyone from Chicago that can help me with some frequencies?

Anyone from Chicago that can help me with some frequencies?

(RSS generated with FetchRss)

Comment on An Intuitive Tutorial on SDR, The Frequency Domain and IQ Data by Drone

While the Author’s Web page is instructive regarding the relationship between I and Q signals with both amplitude and frequency modulation, it stops there and doesn’t go to the next step and show actual demodulation from the I/Q output.

The AM example helps lead the reader to concluding the AM demodulation process is fundamentally simple – by taking the root-sum-square of the I and Q signals. But this is not shown.

However for the ANALOG FM example, the animation shows the inherent problem with trying to demodulate FM from the I and Q signals. It’s not simple at all because the I and Q result is simply the representation of the FM modulated signal to begin with.

It seems to me that there is no simple way to go from the ANALOG FM modulated carrier frequency change to a demodulated analog amplitude change given I and Q, especially over a wide range of modulation frequencies relative to the carrier frequency. Hint: In the time-domain you need to derive the signal rate-of-change between samples, i.e., take the first derivative. (Of-course having higher sample rates and more computational power always helps, but that’s just a brute-force approach.)

But there are ways to do analog FM demodulation from the I and Q signals using digital signal processing. However it is (arguably) simpler to just fall back to analog FM demodulation techniques, especially for direct down-conversion I/Q (and to a lesser extent, low-IF I/Q down-conversion).

N.B., The discussion here targets analog FM. Other approaches should be easier for the likes of digital FM modulation (e.g., basic FSK).

Read more about the inherent difficulties associated with I/Q FM demodulation at these links:

1. Is it difficult to do FM demodulation digitally?

https://www.dsprelated.com/showthread/comp.dsp/142012-1.php

In the Reference-2 below, take a look at: “Figure 13–61. Frequency demodulator without arctangent: (a) standard process; (b) simplified process.”

2. DSP Tricks: Frequency demodulation algorithms

https://www.embedded.com/design/configurable-systems/4212086/DSP-Tricks–Frequency-demodulation-algorithms-

N.B., A printable version of the above link is available here:

https://www.embedded.com/print/4212086

Best 73’s, David WB4ONA

P.S., I would have left this comment on the Author’s Web page, but it seems that’s not possible.

Airspy HF+ test in ARRL DX CW contest [00:01:49]

IC-756p3 IF tap to Airspy HF+ [00:02:53]

endemos Картинки как картинки. Вы про «прелести» очередной вариации на тему «свистка» расскажите. Как NEWGEN.RTL2832SDR …

Avtomatizator пишет:
endemos Картинки как картинки. Вы про "прелести" очередной вариации на тему "свистка" расскажите. Как NEWGEN.RTL2832SDR в работе?
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Широкополосный приёмник из DVB донгла - Страница #541

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Other SDR Devices • What more to buy with Airspy mini — cables, connectors, converters?

Hi, I'm new to the SDR world and will buy the Airspy Mini, my first project will be weather images from NOAA.

I wonder what more I need to buy then the Airspy Mini itself, not sure what antenna, cables etc it comes with. Of course I will have to build the antenna for NOAA but what type of other antennas, connectors, converters will I need to play around and connect it all together. Would be great if you can recommend a list of good to have antennas, connectors, converters, cables etc. for this project and future, would like to have a bunch of stuff at home so I can do what I want without waiting for deliveries :P

Statistics: Posted by fLa — Sat Feb 17, 2018 4:24 pm


Comment on Outernet 3.0: Implementation Details and a 71,572km LoRa World Record by AD5NL

Oh wow nice.

Also I think LoRa can be decoded with othwr SDRs… I believe sdrangel has a demodulator module for it. I assume other plugins exist for other software. I wonder if those will work for Outernet 3.0.

Antennas • Re: wideband antenna for satellite reception

See Tindie or viewtopic.php?f=6&t=2080 for an inexpensive Vivaldi instead of the venerable RFspace one's.

Statistics: Posted by Stry — Sat Feb 17, 2018 2:41 pm


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