This is an amazing video – hand-made vacuum tubes! About 17 minutes long – well worth the watching if you have any interest at all in old equipment!
https://vimeo.com/47812871
Enjoy!
Robert Gulley, AK3Q, is the author of this post and a regular contributor to the SWLing Post. Robert also blogs at All Things Radio.
(Source: RTL-SDR.com)
Nexmon SDR: Using the WiFi chip on a Raspberry Pi 3B+ as a TX capable SDR
Back in March of this year we posted about Nexmon SDR which is code that you can use to turn a Broadcom BCM4339 802.11ac WiFi chip into a TX capable SDR that is capable of transmitting any arbitrary signal from IQ data within the 2.4 GHz and 5 GHz WiFi bands. In commercial devices the BCM4339 was most commonly found in the Nexus 5 smartphone.
Recently Nexmon have tweeted that their code now supports the BCM43455c0 which is the WiFi chip used in the recently released Raspberry Pi 3B+. They write that the previous Raspberry Pi 3B (non-plus) cannot be used with Nexmon as it only has 802.11n, but since the 3B+ has 802.11ac Nexmon is compatible.
Combined with RPiTX which is a Raspberry Pi tool for transmitting arbitrary RF signals using a GPIO pin between 5 kHz to 1500 MHz, the Raspberry Pi 3B+ may end up becoming a versatile low cost TX SDR just on it’s own.[…]
Many thanks to SWLing Post contributor, Thomas Cholakov (N1SPY), who shares his latest video explaining the operation of a simple homebrew AM loop antenna:
Click here to view on YouTube.
Brilliant video, Thomas! I love the fact you included a demonstration with your SDRplay RSP1A as well. Via the spectrum display, it’s easy to see the the loop’s bandwidth and also the gain it provides when tuned to a station.
I love your AM loop antenna as well–such a simple design and ideal for demonstrating the mechanics of a passive loop antenna since all of the components are visible. I’m willing to bet you built this antenna for less than $10. Smart design as it’s both portable and effective! Keep up the excellent work, Thomas! We look forward to all of your future videos.
Many thanks to SWLing Post contributor, Gary (W4EEY), who writes:
I want to recommend an excellent presentation on RF Interference from
the Radio Society of Great Britain (RSGB) Convention in 2015. The
presenter is Ian White, GM3SEK, who has a Blog website here:You can find the presentation video on YouTube here:
Click here to view on YouTube.
The presentation runs for about one hour and contains some valuable
information to help you fight noise and interference in your shack.
Thanks for the tip, Gary!
Last month, on “Pi Day” (March 14, 2018) an upgraded Raspberry Pi 3 B was announced on the Raspberry Pi website. The new $35 B+ sports a few performance enhancements over the original–most notably:
Here’s a short promo video posted with the announcement:
I immediately navigated to my favorite Raspberry Pi source–AdaFruit–and requested a notification when the new units were available to purchase. A few weeks later, I got the notification and placed an order within minutes (you see, when the Pi 3 B was first released, I hesitated a day and had to wait a few weeks for the second shipment!).
I received my RPi 3 B+ a few days ago:
I immediately attempted to put this unit into service but learned that it requires the latest firmware which was only released a week or so ago. If you have have an RPi 3 B+, here’s where to fetch the latest firmware:
NOOBS:
https://www.raspberrypi.org/downloads/noobs/
or if you want Raspbian:
https://www.raspberrypi.org/downloads/raspbian/
and install on SD per instructions here:
https://www.raspberrypi.org/documentati … /README.md
After receiving this latest Pi, I quickly realized I’ve bought a number of Raspberry Pi models over the years and currently have them in service for a variety ofc projects. Here’s a list of all of my current Pi-powered applications:
That’s a total of seven RPi projects that are in service at time of posting!
As I mentioned earlier, I try to buy most of my Pi equipment from the amazing AdaFruit retailer–I like supporting what they do even if I pay a small premium.
But AdaFruit seems to rarely have stock in some of my favorite Pi bundle packages. If I’m buying a Raspberry Pi for a new application, I look for a package with at least a case, a 2.5 amp power supply, a 32 or 64GB MicroSD card, and two heat sinks (though I’m not certain the B+ needs a heatsink). I tend to grab this one or this one from Amazon (affiliate links).
Post readers: Have you ever used a Raspberry Pi? If so, in what sort of applications? How many do you own? Please comment!
Many thanks to SWLing Post contributor, Tudor Vedeanu, who has kindly shared details about his portable Raspberry Pi system which now can run the AirSpy HF+ SDR.
Tudor writes:
I bought the RPi to use it as a Spyserver for my Airspy HF+ SDR.
My main radio listening location is a small house located on a hill outside the city and there is no power grid there (it’s a radio heaven!), so everything has to run on batteries and consume as little power as possible.
My first tests showed that the Raspberry Pi works very well as a Spyserver: the CPU usage stays below 40% and the power consumption is low enough to allow it to run for several hours on a regular USB power bank. If I add a 4G internet connection there I could leave the Spyserver running and connect to it remotely from home.
Then I wondered if the Raspberry Pi would be powerful enough to run a SDR client app. All I needed was a portable screen so I bought the official 7” touchscreen for the RPi.
I installed Gqrx, which offers support for the Airspy HF+. I’m happy to say it works better than I expected, even though Gqrx wasn’t designed to work on such a small screen. The CPU usage is higher than in Spyserver mode (70-80%) but the performance is good. Using a 13000 mAh power bank I get about 3.5 hours of radio listening.
I made a video showing how it works:
Click here to view on YouTube.
This is fantastic, Tudor. Thanks for taking the time to put together a video for us. I’ve just ordered the latest Raspberry Pi 3 (Model B+). It has slightly more horsepower than the previous Pi3. Tudor, you’ve inspired me to grab the 7″ touch display as well and try my hand at running the AirSpy HF+ portable.
I’m not sure if the Raspberry Pi 3 will be able to record spectrum without hiccups, but it’s certainly worth a try.
As you tweak your system, please keep us in the loop!
Finished Backpack Loop 2.0 and accessories assembled together
Many thanks to SWLing Post contributor, TomL, who shares the following update about his homebrew Backpack Shack 2.0 portable loop antenna:
by TomL
This is just a quick Field Update for my Backpack Shack 2.0 antenna. It is not the most powerful antenna but in the right location it can be useful, especially with using an SDR. It was used during February in two Forest Preserve (County Park) locations outdoors and once from my usual Grocery Store parking lot!
Please excuse some of the computer generated noises (caused by a slow CPU) as well as some audio connector problems on a couple of recordings.
Each Time is in UTC and Frequency in kHz. Where can you hear unique programming like these samples except Shortwave Radio??? Enjoy!
VOA, @03:00 on 6080 kHz in English from Sao Tome towards Africa (backside of their antenna, opposite of my location)
Audio PlayerChina Radio Int’l, @23:00 on 9415 kHz in Vietnamese from Beijing (not sure if this traveled around Antarctica to get to me or a backside of their antenna over the North Pole?)
Audio PlayerWHR, @15:59 on 9965 kHz in Korean from T8WH Palau
Audio PlayerMighty KBC, @01:48 on 6150 kHz in English from Nauen Germany (announcer sound effects included!)
Audio PlayerVoice of Greece, @20:34 on 9420 kHz in Greek from Avlis (unique stylized Greek music, INTERESTING artistic expression)
Audio PlayerVatican Radio, @20:27 on 9660 kHz in English from Vatican City to Africa
Audio PlayerWINB, @21:30 on 9610 kHz in English from Red Lion, PA USA (a FUN song about promoting Radio listening!)
Audio Player Audio PlayerI will be working on a larger version of this antenna to transport in my car as well as a small VHF loop antenna for the outside deck for Air/Police/Weather scanning.
Hope to report sometime this Spring.
Thank you so much for the update, Tom! It looks to me like you’re having an amazing time with you homebrew loop in the field!
As always, keep us in the loop! (Yeah…bad pun, I know!)