HF Airspy Mini + Spyverter + Random Long Wire

 

Hey you. Look what I got. Thats right, I got an airspy mini & spyverter :)

I have had the airspy mini for a while now, I use it for listening to satellite communications. It seems to be my go to SDR, having also a RTL-SDR and an SDRplay RSP1. I won't go into reasons why it is my go to more than that it is more able to pick up signals and is more user friendly with my computer, and has bias tee.

my rtl sdr HF usb dongle - beginner level on HF?

I wanted to see if I can extend it's capabilities to using HF bands (0-30Mhz) just to be able to explore RF and learn a bit more. I tried with my RTL SDR HF dongle which gives basic results (0-14Mhz) but lacks bias tee and has EMF noise in the waterfall, the SDRplay has good potential but it is so terrible at integrating with SDR# or SDR++ on Linux or Mac it is just not worth going down the Rabbit Hole; if this issue is sorted then I might come back to SDRplay.

So, I bought myself an Airspy Spyverter last week and here are my first impressions. I bought all devices myself and I am not doing paid promotions or product endorsements.

Firstly, the Airspy and Spyverter do not come with a printed manual, so you must research ho to hook it all up correctly or else you could damage the devices. I connected my Airspy Mini & Spyverter up like this:

note the position of the micro usb socket on the spyverter. It helps to know this for orientation. Also it is suggested not to connect usb power to it while at the same time using bias tee power, as it might cause damage.

I get it connected like this:

I stuck on the self adhesive heat sinks to the airspy mini as i was worried about the amount of heat it produces - I am told on forums that the very high heat is a normal feature of airspy mini, similar to the heat produced from running Jetson nano's, Raspberry pi 3's or 4's wihout heatsinks or fans attached.

My antenna for basic first time HF reception is a random long wire antenna connected to a 9:1 unun. I use over 16m of wire for the main element, and a few metres of wire going to a grounding source which is supposed to reduce electrical noise. in between I use a self-made unun/balun using a ferrite ring, wire, and connectors housed in a plastie box:

my homemade 9:1 unun/balun

And so onto the results of the Airspy mini + Spyverter HF combo. Am I pleased?

Well, it's a mixed bag. I am only a week or so into using it so perhaps I have not got the setup creases smoothed out yet. 

Things I like about AirSpy Mini + Spyverter:
1 - this combination gives me the HF 1-30Mhz I was looking for (the rtl-sdr only does 0-14Mhz HF).
2 - the gain controls seem to actually have an effect on signal performance.
3 - it is more straight-forward to get up and running receiving signals.
4 - it has bias tee power.
5 - I am definitely getting more radio stations than I did with either RTL-SDR HF dongle or RSP1 dongle.
6 - The stations I get are more clearer than when using either two other dongles.
7 - using the Airspy Mini + Spyverter with SDR# software, it is the best combination I have used to fine-tune audio and noise reduction to achieve clear speech even in high static, faint HF radio stations. It almost seems like a magic trick sometimes.

Things I am yet unsure about Airspy Mini + Spyverter:
1 - Is my location in the centre of a busy built up urban area causing me to pick up more EMF and RF noise using the more sensitive Airspy mini?
2 - What is causing the different wave pattern in the SDR software?
3 - Is my antenna sub-par?

Using the various SDR devices I own, they all produce different and varying outcomes on the RF waterfall of various SDR computer software. As a mostly MacOS user I have used GQRX, CubicSDR, SDR#, and SDR++.

I tend to use different software packages mostly because as yet, I haven't been able to find a one-for-all complete software package yet. SDRplay devices are the big stumbling block here. My RSP1 I can only get working using CubicSDR on Mac or SDRuno or SDR# on Windows 7/10. I  very rarely use my RSP1 maybe once a month I take it out the box, and that is just to compare against other devices.

SDR++ comes close to being the most one-for-all complete package, but as yet, it does not have the magic audio processing that SDR# has. And as you may realise, SDR# is a Windows only package. Having a Mac version would be tremendous. Many people would be happy.

So onto my signal tests.

Using my Airspy Mini + Spyverter combination, it does undoubtedly produce lots more radio stations and listenable signals for me than my other devices. It is as simple as that.

However I am now contending with some other things which I want to know more about and try to find solutions for.

Mostly. What is causing these RF peaks?

When I read up on HF sdr, I saw waterfalls which looked like this:

Nice, flat spectrum, with nice clear well-defined station peaks. 

Using my Airspy mini + Spyverter setup I get this:

I get the nice clear well-defined station peaks. But I also get this huge fat arch of doom. Why do I get this? What is causing it? Why! Why! Why! My life!

I don't get this result using RTL SDR HF dongle, but I also get fewer clear stations. Here is my result using RTL-SDR HF dongle:

 

Is it because the Airspy mini or Spyverter is damaged?
Is it because the Airspy mini and Spyverter are more sensitive to ALL RF signals including noise?
Is it because of my long wire antenna?
Is it because of my location and my antenna position (in the attic of my end terrace urban house)?

I can reduce this mound by reducing the airspy mini gain to level zero or 1, but also I reduce the clear stations too, they are synchronous:

Airspy Mini + Spyverter set to Linear gain level 16:

 

 

 Airspy Mini + Spyverter set to Linear gain level 8:

 

 

RTL SDR HF Dongle set to max gain level 49dbi:

Using Airspy min + Spyverter this mound also exists all through the HF reception, an example at 7Mhz is here:

I have tried to correct using:
- Ferrite chokes on the wires - no noticeable difference

Then:
- Testing on a different computer, a laptop:

Laptop - Airspy Mini + Spyverter + Long Wire antenna set to Linear gain level 16: 

 Laptop - Airspy Mini + Spyverter + Long Wire antenna set to Linear gain level 8:

 It seems to be a different RF noise pattern than with Desktop computer. So what now?

- Testing with a different antenna:

I try also using a simple telescopic antenna with 'First test' Desktop like this:

Airspy Mini + Spyverter set to Linear gain level 16 (using simple telescopic antenna): 

 

It looks like the RF noise 'Desktop' mound is gone, but I think it is because the antenna is simple, it is not picking up stations as good perhaps less sensitive? It is similar to Airspy Mini + Spyverter set to Linear gain level 2 or less.

But because my RTL-SDR HF dongle at full gain is not making this, then it could be assumed that it is something to do with the Airspy mini + Spyverter combination? or Long wire Unun Antenna? What next?

It seems that with the Airspy mini + Spyverter combination it is much more sensitive to RF noise from various things perhaps?

So what next?

Further tests:
- Testing outside far away from the house.
- Testing using laptop on battery power instead of AC power adapter.
- Testing using a antenna far away from house.
- Somehow shielding from RF the Airspy mini more? Or is the noise coming from USB computer?

Will update soon.

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.