My HRPT setup

Hello there, I would like to share with you my HRPT satellite setup which I use to collect weather images.

It is a 1m folding parabola with a custom antenna feed tuned to 1698Mhz. It all mounts onto a tripod, but I tend to hold it and handtrack the satellite. It is extremely lightweight and as such it is comfortable to hold for a 14 minute pass without feeling like you need to put it down. It allows you to track very accurately.

It all fits nicely together, and it can be quickly taken apart and stored safely.

I use a Nooelec Sawbird Goes+ LNA along with an Airspy Mini. I power the Sawbird using an external Bias Tee because the spec sheet says that the airspy mini is unable to power the LNA effectively.

Sample images using this setup:

NOAA 19

Meteor MN2

I capture using satdump, I use the live decode feature and the image is produced just after the satellite has passed.

If you would like one of these setups please get in touch or if you have any feedback please let me know.

Thanks for reading :)

Harmonic Drive Antenna Rotator

Here is an example of a Harmonic Drive rotator I have been working on.

Video example 1:

Video 2:

The antenna in this example is a 1546Mhz Helical.

Thanks for reading.

:)

What...The...F....Unun?

 

Hi, Yesterday I decided to test a long wire antenna I got cheap last year. It came with a 9:1 Balun...Or so it was advertised. Anyhow, I decided after first test that it worked, but I wanted to open it up and have a look inside to see what was going on.

 Opening her up there seemed to be a spare loose wire. So I posted a quick question about it over to the nice bunch at rtl-sdr group on facebook. It quickly turned heavy, and we all debated Balun vs Unun until the sun came up.

But some great information was given, and we decided that this cheap WTFun must in fact be (possibly) a type of unun. It is still ongoing lol. Balun/Unun/Autotransformer Balun. You tell me in the comments.

So anyway, today I decided to do a simple test to see if any of the suggested alterations help with signal noise or performance.

To test, I soldered some dupont connections to quickly allow me to change through the ideas.

Pin 1) dupont pin soldered to original loose wire which we think should be counterpoise/GND or to pin 2

Pin 2) Another dupont pin to test the connection that Watcharapong Chuginda did

Pin 3) Another dupont pin which runs a few metres of wire to a crocodile clip to connect to a good ground source.

Pin 4) Another dupont pin to connect to Ground/Counterpoise on pin 3

Now to test (p.s i don't have an antenna tester yet, so I have to just compare in SDR software sorry for my amateurishness haha)

So onto the quick test.

Test number one) - in original format

 

Connecting up the long wire to the WTFun Red connector, and connecting RTL-SDR device to BNC connector at the base.

Picking up some signals on 19Mhz. It seems to be a good day to get HF signals, yesterday was stormy and things were dropping in and out a lot. from 1Mhz-30Mhz I can receive some stations.

I am however getting quite a lot of static and what seems to be POCSAG interference/overloading as I am in between two hospitals. There must be a lot of pagers going off.

Test number two) Pin 1 to Pin 3

Ok. Looking at the same 19Mhz station, it seems to be a little bit stronger, clearer, less noisy.

A marked improvement. The POCSAG interference seems to still be there. But stations which were inaudible before are now listenable. I can pick up stations at 7Mhz. 9Mhz is much more strong than before.

Test number three) Pin 1 to 2

 

 

This connection was described by Watcharapong on the RTL-SDR group.

 

Seems to be between the factory wiring and setup two. There is a signal improvement, however it does not improve as much as test two. It feels a bit different does test three.

Test number four) Pin 1 to Pin 2 - and - Pin 3 to Pin 4

This setup was suggested by Harold over at RTL-SDR facebook group. It seems to work similarly as test two and three.

The same 19MHz station comes through well. I'm starting to struggle to hear any major differences to the tests apart from the original wiring as that was definitely worst of all.

Bonus test five) - Pin 3 to Pin 4
For some strange reason... I don't know why, this wiring setup seemed to be best of all.

Things just seemed least statically noisy, stations seemed clearest. I have no idea how or what the maths onvolved is, but it's just an observation. It is a narrow margin but I think this might be the best. Correct me if I am wrong.

Conclusion
It seems for now I am choosing test 5 setup. it is all about personal preference, but at the time i did this test it seemed to give the clearest sound.

The test shows that connecting a ground or counterpoise is the most important thing to add to this 9:1 WTfun (balun or unun?) to obtain a much improved signal compared to how it arrives from the store. I would say it is junk as it comes from the store. However making a simple ground connection will significantly improve it to the point that I feel I already have made progress with my HF reception.

I would like to thank all the RTL-SDR contributors over at the Facebook group for making suggestions and providing feedback. I hope this provides some answers to this device for others.

Thanks for reading.

Update:

For comparison to the wtfunun from china, this morning I made a true 9:1 Unun using a micrometals toroid and It provides significantly stronger cleaner HF reception. So there you go
Thanks again for helping. I plan on later removing the insides of the wtfunun and placing the micrometals unun inside.

Reference Circuit:

Update 2:
I rewired the Wtfunun. I learned that if we follow the above unun schematic then the wtfunun is wired backwards. I did not have to rewind the wiring just change the connections to the above image.

rewired to match the wiring of the micrometals unun i made. Now testing it with gqrx

 

rewired wtfunun to 9:1 unun top, micrometals 9:1 unun bottom

 

It is similar. But different if we look around 1Mhz the radio stations are much higher peaks.

Now, I must work on reducing overall RF noise
- setup long wire outside instead of attic
- Try SDR HF using battery power instead of household mains
- Go out to the countryside and test
- Try a different HF adapter such as Airspy spyverter.

I read that most RTL SDR devices use a 1.2v switching power supply and that it is a source of harmonics and RF noise. I could modify the pcb, but I may just search for a better noise-free device.

Thanks.

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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