Auto Transcribing International HF radio stations

 For a while I have been enjoying using and learning about Software Defined Radio. I think covid lockdown in 2020 allowed society to take part in hobbies and learning much more easily than at anytime I can recall, and for me I found interest in listening to new frequencies.

I got myself a simple HF setup.

This was my first SDR i purchased. I had no idea about stuff and just bought because it looked funky.

I plugged it in and learned all the things - Zadig drivers, SDR Sharp, GQRX, Tuning, Bandwidth, Modulation and so on. My knowledge grew and grew.

Eventually I learned that it can be set to use 0-30MHz or HF radio frequencies too. in GQRX you had to set the device string like in this image

I also got myself a better antenna than the mini whip that came with the SDR package. I went with cheap advice and went with something called a long-wire antenna.

It is just a 22m length of wire and a 9:1 balun. I think a balun can be bought now for a couple of bucks, and wire can be gotten for pennies. In the picture are a green and red coil of strong string to help you throw the wire over a high tree branch and secure it outdoors, but I never really bothered with that as I wound the wire indoors around my attic space.

All in all this gave me better reception that I had with the mini whip antenna, and I could get some international stations; some Russian, some Chinese, some Spanish, Italian, German, Indian. But I had no idea what they were saying. I wondered sometimes how I could solve that problem and on night I came up with an idea.

I learned that I could take the audio headphone out from one device - A laptop or Smartphone. And connect that to the mic input on a smartphone. Then I could just use google translate or microsoft translate apps to transcribe the spoken adio into understandable text. All processed in live real-time.

I tried it on a chinese station; they talked about increased national production over last year, progress, and always progress. Then I tried on a Russian station and they spoke about russian writers. Italian radio spoke about Taylor Hawkins and the Foo Fighters. Indian music translated as lost love, infidelity and punishment.

So there. I had a better understanding of all these stations broadcasting thoughts and feelings coming from their own countries. I no longer had to imagine ehat they were saying, no more worries about the 39 Steps, Invasion, Boy scouts Brigades or other paranoid shine.

My tests are still ongoing, and I have also learned how to use live translate in a web browser. I get similar results to phone app translate, except I don't seem to get always on, i only get a few seconds translation before I have to press the button again. But it is an option. I use my iMac with software called soundflower to pipe the audio into the browser.

Thanks for reading.

HRPT NOAA & Meteor Satelite

So a few updates on receiving HRPT signals. It has been a very exciting few days! The sun has arrived, longer days, clear blue skies. So it has given me the motivation and comfortable warmth to spend a whole day in the workshop and this is what I produced.

I made a few feeds for an antenna idea.

The signal i got with the patch antenna was meh ok. I tried it out with Inmarsat on GQRX.

 Next I tried the same with the Helical mounted on a DIY parabola

A much stronger signal. For both tests i used a single LNA to boost signals.

Here's my simple setup:

I just cable tied it to a cheap tripod.

So next up, I added a second LNA to the chain

The signal is really good now. I used SDR++ also just to have fun.

Here is a picture of both my LNA in a makeshift power connection

Later in the day I modified the First LNA to power via Bias Tee on the Airspy mini, and also power the second LNA by linking a +V wire from the modified LNA to the second LNA, no GND wire needed.

Here is a short video of this setup receiving Inmarsat

By now the evening pass of Meteor M2 and NOAA 19 is approaching so we try this setup to receive these

Here is Meteor M2 1700Mhz HRPT

And just after came NOAA 19 1698Mhz HRPT

All in all I am happy with this progress.

I handtracked both satelites, however I have built an Antenna tracker rotator and I will of course repeat using this at some point over the spring and summer. I also plan to receive other sats such as Metop, Fengyun, Proba, and other L-BAND signals. If you are interested in receiving HRPT let me know your own progress, tips and improvements. All in all, my HRPT antenna probably cost around £20 to make, excluding LNAs and SDR.

Thanks for reading. Feel free to comment.

Using Spyserver

 

I am building my second antenna rotator this month, one which allows a much larger dish to pick up L-Band. As it will be outside well out the way of my desk imac, I have to find a way to communicate with the rotator from a distance. I decided to check out Spyserver by Airspy which can be downloaded from the link.

Spyserver is a way to send your radio signals remotely over wifi to your desktop or laptop. It is a great idea for many situations. So I gave it a shot to use with rotator 2.0.

The devices I tried to use:
Raspberry pi Zero W - Did not work: Far too underperforming, not enough GPU or Ram
Nvidia Jetson TK1 - Working.
Did not work: The Airspy deb files for spyserver include an option for Armhf so I tried to use this one. The Jetson TK1 is 32bit. However for now I could still not get it to stream.
Updated: It works on TK1 32bit > I use 'Spy server - SDR Server for Linux ARMHF' from this link
Then I install Airspy on TK1 > sudo apt-get install -y airspy

Then when I run 'airspy_info' i get error:
airspy_info
airspy_lib_version: 1.0.7
airspy_open() board 1 failed: AIRSPY_ERROR_NOT_FOUND (-5)

if I run sudo airspy_info i get success:
airspy_lib_version: 1.0.7
Found AirSpy board 1
Board ID Number: 0 (AIRSPY)
Firmware Version: AirSpy MINI v1.0.0-rc10-0-g946184a 2016-09-19
Part ID Number: 0x6906002B 0x0000xxxx
Serial Number: 0x022C61C82Axxxxx
Supported sample rates:
    6.000000 MSPS
    3.000000 MSPS
Close board 1

So to get airspy mini working in gqrx or spyserver etc we have to run:
sudo usermod -a -G plugdev `whoami`
then reboot TK1
And success! Spyserver and gqrx running perfectly.

Jetson Nano 2GB - Works Like a charm! I used the .deb file for ARM64.

Editing the .config file is as straight forward as it gets, there is nothing there to really confuse.

you can edit it directly on the nano, or ssh then using:
sudo nano spyserver.config

The Spyserver is setup to connect through the Jetson Nano using 0.0.0.0:5555 as a default address

On your main computer, you can connect to spyserver using either SDR# or SDR++ using the IP address of you jetson nano followed by the 5555 port number.

If you have good internet, very fast wifi dongles, powerful computer, you should have no problem streaming an airspy mini at 6Mbps, or you can use 3Mbps and reduce the system demand. There are other tweaks you can perfrom to reduce demands too in the config file.

I am now wondering if Raspberry Pi Zero 2 W will run spyserver. It only has 512MB Ram and I think the wifi is not high speed as I cannot find detailed specs about it's wifi adapter. So it's two possible faults are not enough ram and low bandwidth wifi.

For now, I will stick with a 2GB/4GB Jetson Nano and 1200Mbps wifi dongle.

DIY Rotator

Current state 👌

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SDR++ on Jetson Nano

 

I compiled and installed SDR++ on my Nvidia Jetson Nano :)

How does it compare to say GQRX. I think SDR++ runs faster, has a few more options which are familiar to SDR# users. One feature I like with SDR++ compared to GQRX are the gain options for my Airspy Mini - it has Sensitive/Linear/Free whereas GQRX only has Free.

I also like the Module Manager is SDR++ which allows for the addition of extra functionality such as Meteor decoding, Gpredict integration.

More info: https://github.com/AlexandreRouma/SDRPlusPlus/issues/446

Jetson stats seem favourable:

Autonomous Satellite Tracker & Decoder

 Hi there, I would like to share with you my Satellite tracker and Decoder.

I am using: 

Nvidia Jetson Nano with latest JetPack 4.6 - (https://developer.nvidia.com/embedded/jetson-developer-kits)
DIY Antenna Rotator - (https://wiki.satnogs.org/SatNOGS_Arduino_Uno/CNC_Shield_Based_Rotator_Controller)
GPredict - (http://gpredict.oz9aec.net/)
SatDump - (https://github.com/altillimity/SatDump)
Airspymini SDR - (https://airspy.com/airspy-mini/)

Here are some samples from my setup:

 live decoding testing with Satdump on Jetson Nano

 building my rotator

 all hooked up and ready for testing

Once we are successful with the rotator it is time to exercise while it does it's thing :)

A few other photos and things from my build

testing gpredict with rotator

gpredict tracking

 

Meteor-M2 capture - October 2021

 

FY-3B

 

Jetson Nano Case + USB hub

 

My Airspymini goodness

 

I even made an oled

Couple of videos showing rotator function:

Thanks for reading :)

International Space Station Broadcast 12th October 2021

 Today I was able to capture audio broadcasting from the iss.