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8 votes
Accepted

Calculating satellite passes without an internet tracker?

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 ...
tomnexus's user avatar
  • 11.3k
4 votes
Accepted

Lack of understanding in the APRS specification for LoRa

Why do I have to send these characters at the beginning of the message? It's just an arbitrary header that this group of people used to identify APRS messages, and distinguish them from other packets ...
hobbs - KC2G's user avatar
  • 12.4k
4 votes

Is there an FT8 or other weak-signal digital mode specification available?

The closest I could find to a specification for FT-8 was on the Wikipedia page for WSJT. In answer to your second question. I lead an open source project that is designing an implementation of the ...
Michelle Thompson's user avatar
4 votes

Problem with sample rate

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 ...
hotpaw2's user avatar
  • 13.4k
4 votes

Problem with sample rate

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 ...
tomnexus's user avatar
  • 11.3k
4 votes
Accepted

How do I write a modem for DireWolf?

Actually, direwolf already supports higher data rates since 2017; it will use the G3RUH modem for a speed of 9600 or higher. As shipped it can be configured up to 40000 bps. But it's a mistake to ...
hobbs - KC2G's user avatar
  • 12.4k
3 votes

Calculating satellite passes without an internet tracker?

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 ...
user10489's user avatar
  • 6,455
3 votes
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How to trim out background noise GRC

Since you tagged your question with GNU Radio, I am assuming that is your SDR software package. If you look under level controllers, you will find a function block called "Power Squelch". This ...
Glenn W9IQ's user avatar
  • 18.6k
3 votes

How do blind hams operate?

I'll answer the first part of your question, Ronald. I once witnessed a blind ham (WD8PIC) operate. His solid-state transceiver had a speech synthesizer that audibly spoke the frequency when the ...
Mike Waters's user avatar
  • 8,023
2 votes

Is there an FT8 or other weak-signal digital mode specification available?

I do have the specification for JT9 if that is of interest to you. It is currently in the form of a pdf. Would you like it emailed to you? Or would you prefer I paste it on this forum as ASCII text (...
B. Horn's user avatar
  • 21
2 votes

Is it possible to generate rf by directly programming a pc parallel port?

"Is it possible to generate rf by directly programming a pc parallel port?" Yes, you can. In fact any "alternating current" will produce RF, and a "port" (parrallel or other) from a "computer" can ...
Edwin van Mierlo's user avatar
2 votes
Accepted

Turning raw APT data into an image

The data is AM modulated on the 2.4 kHz subcarrier, with 256 different levels representing a single value from 0 to 255. It's a scanline every 1/2 second from the cameras with sync and telemetry data ...
ElectroNeutrino's user avatar
2 votes

What is the format of Yaesu FT3D's QSOPCTDIR.dat and QSOPCTFAT.dat files?

...
Gabriel's user avatar
  • 21
2 votes

How do blind hams operate?

There are accessories for some radios that provide a speech capability. Here is a link to a web site, HamRadioAndVision, that has some information. https://www.hamradioandvision.com/accessible-...
Jim's user avatar
  • 1,698
2 votes

How to get the "real" number of samples coming in an sdr

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 ...
hotpaw2's user avatar
  • 13.4k
2 votes
Accepted

Not able to understand some operations in rtlsdr library in python

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 ...
hotpaw2's user avatar
  • 13.4k
1 vote

Brandmeister API - How to get the Last Heard from the API

Stephan from BM responded with the API does not provide last heard.
Zippy's user avatar
  • 121
1 vote

Is an Icom radio’s model ID info available via a CI-V command?

ICOM uses "other" CI-V commands to interrogate the radio. If you have any of the radios which use their "Cloning Software" you will notice that there is an "Information" ...
guitarpicva's user avatar
1 vote

Yaesu FT817ND + (Bluetooth) CAT control + ESP32 microcontroller: reading SWR "programmatically"?

it looks like the flrig folks have it sorted out. From the flrig source file in src/rigs/yaesu/FT817.cxx: ...
webmarc's user avatar
  • 4,234
1 vote

Not able to understand some operations in rtlsdr library in python

The number of samples to read. Probably because whoever wrote it wants the graph to read in MHz rather than Hz.
hobbs - KC2G's user avatar
  • 12.4k
1 vote

What value goes in the AX.25 PID field if the Layer 3 protocol is not defined in the standard?

The AX.25 Amateur Packet Radio Link-Layer Protocol Version 2.0 October 1984 document states: "All forms of yy11yyyy and yy00yyyy other than those listed above are reserved at this time for ...
John's user avatar
  • 156
1 vote

Is there an FT8 or other weak-signal digital mode specification available?

I don't believe FT8 has a complete specification besides the source code, which is openly available. RTTY is an option. It doesn't need much of a specification since it's so damn simple. PSK-31 is ...
Phil Frost - W8II's user avatar
1 vote

USRP: Are RX and TX on the same or different channel for single daughterboard?

The TX channels are separate from the RX channels. Hence, there will be a singkle, dual-stream RX streamer, and a single, dual-stream TX streamer. The subdev strings in your pseudocode aren't doing ...
Marcus Müller's user avatar

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