The simplest might be to use an app.
On Android, Heavens Above, a product of the 25-year-old website of the same name, stores the orbital elements of the satellites of interest, and does the pass calculations on your phone.
The app uses the GPS to find your location. It likes to get fresh elements from the Internet on startup, but it caches them, so as long ...
The RTL-SDR interfaces to your computer via USB. The USB interface and driver will buffer the data and send it to your software at the requested sample rate on average (baring underflow due to software glitches), but with varying timing due to interface jitter. The RTL2832U USB is likely sending larger chunks of data over USB in blocks of far more than 512 ...
512 samples should take 256 microseconds, so your times look about right.
The exact time it takes to execute those lines of code will depend on the rest of what your computer is busy with. And it's unlikely that the elapsed time counter will be accurate to better than 10 us anyway (but I may be wrong, try it yourself by timing a delay loop).
Whats slightly ...
You have to provide the -i option to invert the signal in order to decode it properly. The lowpass filter is not really required as this is a quite strong signal (but does not harm either).
$ ./rs41ptu -i --crc -vx wav/20140717_402MHz.wav
bits : 8
channels : 1
[ 5047] (K1930308) Do 2014-07-17 12:32:13.999 lat: ...
To track the satellites, you need the Keplerian TLE orbital coefficients. Once you have those, you can track the sats without internet access. The TLE's are accurate enough for about a week. The TLE file format is standardized and works with nearly all the tracking software, and most software either downloads them on command or can import from a file.
Listen tcp 0.0.0.0:5000 bind address already in use.
This sounds like a somewhat generic error, not necessarily related to your AX.25 software itself but certainly a bummer to encounter it while setting up!
What this means is the software you're trying to run wants to listen on port 5000, on all network interfaces (the 0.0.0.0 part). But something is ...
I have version 2.1.0. Under File->Settings, select the General tab. There is a box marked "Show DXCC, grid, and worked before status" that can be check marked. I use that to identify stations I have worked before.
The real number of samples from an RTL-SDR is not available via the USB interface. The RTL2832U chip samples at 28.8 Msps, but then mixes and downsamples the internal samples to lower rate IQ samples at from 240k to about 3 Msps, to allow transport over its slower USB 2.0 bus. The front-end R820T tuner can first downconvert VHF and UHF signal to a low HF ...
More than one block can be read into the psd if you want a result that is averaged (thus usually smoother) over several blocks.
A sample rate in Hz can be divided by 1e6 if you want a spectral plot labeled in MHz, instead Hz.
You may like checking out svxlink. I've had success setting it up on a Raspberry Pi, interfaced with a baofeng (pls don't judge) to accomplish VM (as well as successfully interfacing with EchoLink) in a simplex configuration, but only as a prototype... I haven't experience running it for an extended period.
Obviously, you can interface the RPi with the radio(...
I can imagine a device that listens on a ham frequency to record voice messages and decode commands, and then retransmits recorded voice messages on the same frequency on command. Such a device would be relatively easy to design and build. But there are legal issues, at least in the US.
Legally speaking, I presume that you're talking about an automated ...
With correct settings for the transceiver's CAT interface in the Winlink software, Winlink should be able to control the transceiver. There should be no need for another "computer control program" interfacing with Winlink.
Remove all copies of your Echolink program and install it from a reputable source. This sounds like a virus or worm.
From my experience, Echolink runs fine and the only files created are in the %temp% folder.