We've recently seen a few submissions about a new low cost active magnetic loop antenna called the K-180WLA which sells for around US$50 - US$60 over on eBay and Aliexpress. While it appears to be very similar to the well known MLA-30 loop, it's main defining feature is that it's power feeder is battery powered via a built in Lithium ion cell which would make it useful for portable operation. It also advertises a wide usable frequency range of 0.1 - 180 MHz with an amplified gain of 20 dB. They note it can also be pushed up to 450 MHz with reduced gain of 8.9 dB. The battery run time or power draw is not advertised. They write:
The P.BOX feed box has a built-in 3.7V 18650 flat-head lithium battery with integrated power supply module. It is the only active antenna that does not require an external power supply and integrates a charge management chip. The MICRO USB charging port is compatible with the 5V charging head of Android phones. And charging cable, very easy to use.
UHF low-noise preamplifier is used. The gain flatness is very good within the ultra-wide operating frequency of 0.1-180MHZ. It provides a gain of about 20DB, even when working to 450MHZ gain, there is still about 8.9DB.
The receiving frequency covers long wave, medium wave, short wave, FM broadcasting band and VHF aviation band. The small ring diameter 55CM is simple to set up. It can be set up outside the window, balcony, terrace and roof. Lovers erected.
All the screws of the antenna are made of 304 stainless steel, and the preamplifier box is fully waterproof, which can be used for long-term outdoor wind and rain.
Suitable models include Desheng S-2000 PL-660 PL-880 ICOM R71E YAESU FRG-8800 and all short-wave receivers, especially for SDR receivers.
The antenna is equipped with a dual SMA male adapter cable, an SMA to 3.5 plug adapter cable, and an S2000 BNC adapter, which means that your radio can be used with SMA female, BNC, and 3.5 jacks. Requires additional accessories. Receivers and radios with other interfaces need their own adapters.
SMOG-P is a Hungarian nano satellite developed by BME University. It's payload consists of an on board spectrum analyzer that is designed to measure electromagnetic pollution (electrosmog) from space, and to also monitor the DVB-T spectrum. It currently holds the title of the world's smallest satellite in operation. ATL-1 is another Hungarian satellite this time developed by ATL Ltd. Its mission is to test a new thermal isolation material in space and to monitor the DVB-T spectrum.
To receive telemetry from these satellites you can use a Raspberry Pi, RTL-SDR, Yagi, and optionally an LNA and filter. In his post Zoltan shows how to install the SMOG-P decoder, and provides a script that automatically decodes, uploads packets to the BME University server, and archives old IQ files and packets.
We note that if you wish to receive these satellites, now is the time to do so as these nano satellites are in a very low orbit and only have an orbital lifespan of only 6-8 months total.
Thank you to M Khanfar for submitting his YouTube tutorial on how to build a passive IMSI catcher with an RTL-SDR. He writes:
In this video im processes of easy step by step building a passive IMSI catcher. The purpose of this video is to be educational - to highlight the ease of which these devices can be built, and to practically show how privacy is already being compromised today ! easy step by step install and running under virtual machine Ubuntu 18.04 and cheap SDR dongle! .
Intro An IMSI catcher is a device commonly used by law enforcement and intelligence agencies around the world to track mobile phones. They are designed to collect and log IMSI numbers, which are unique identifiers assigned to mobile phone subscriptions. Under certain circumstances, IMSI numbers can be linked back to personal identities, which inherently raises a number of privacy concerns.
The purpose of this video is to be educational - to highlight the ease of which these devices can be built, and to practically show how privacy is already being compromised . Nothing in this video is necessarily new, and those with less than honest intentions are most certainly already using these (or similar) devices.
This video walks through the processes of building a passive IMSI catcher, which is distinctly different from traditional IMSI catchers in that it does not transmit nor does it interfere with cellular networks in any way.
Traditional IMSI catchers are illegal in most jurisdictions due to the fact that they transmit on cellular frequencies (which requires a license), and that they essentially perform a man-in-the-middle attack between a phone and mobile base station (which breaks all sorts of anti-hacking laws). A passive IMSI catcher does neither of these.
How it works The passive IMSI catcher works by capturing IMSI numbers when a phone initializes a connection to a base station. The IMSI is only disclosed during this initial connection. In an effort to protect privacy, all subsequent communication to that base station is done with a random Temporary Mobile Subscriber Identity (TMSI) number.
This means you will only collect IMSI numbers for devices as they move between base stations. Traditional IMSI catchers work differently, by spoofing a legitimate base station and forcing subscribers to connect to itself. They have the added ability to collect data about stationary devices, and can potentially have a more targeted range.
The only hardware required is a PC and SDR receiver that supports GSM frequencies. Generally this means 850/900/1,800/1,900 MHz. Most of the inexpensive RTL2832U based receivers have an upper-frequency range of about 1,700 MHz. You can get by with one of these, but of course, you won't be able to listen to stations at 1,800 or 1,900 MHz.
--- you can easy search GSM towers around you and show its frequencies then select specific tower then access its HLR data, then you can locate tower location in google map when you have specific data collected from SDR in terminal like : MCC,MNC,LAC,CELLID , then you can easy add these data in this website: https://cellidfinder.com/cells then locate it on map, and you can use IMSI number that you sniff to collect details info from database that have access with subscription to full database from this website :https://www.numberingplans.com
Over on the SWLing Post Blog Thomas has uploaded an excellent tutorial showing how you can build your own YouLoop (aka a Noise-Cancelling Passive Loop). If you've been following our previous posts you'll know that we recently started selling the "YouLoop" which is designed and produced by Youssef from Airspy. The YouLoop is a passive loop antenna designed for HF reception, but also works well up until VHF. The main catch is that you need to use it with a receiver with a low noise figure front end, like the Airspy HF+ Discovery (SDRplay units should work well too). The RTL-SDR Blog V3 in direct sampling mode does somewhat work with it to an extent, but RTL-SDRs relying on upconverters for HF will probably see poor results.
We are selling the loop in our store for $34.95 including free shipping to most countries. Batch 2 is currently in preorder, but is almost sold out and should begin shipping soon. Batch 3 will also be available for preorder soon and is about 2 weeks away from shipping. We also expect there to be a high quality pre-amp available for sale in a few months too which will help those with higher noise figure radios or longer feed line runs.
Alternatively, as the YouLoop is a relatively simple and openly shared design it is possible to homebrew your own if you want to. Over on the popular SWLing Post blog, author Thomas has written up a full tutorial on hombrewing your own. The parts you need include coax cable, a BN-73-302 wideband 2-hole ferrite core, magnet wire, heat shrink tubing and electrical tape. The guide takes you through the process of winding the balun and constructing the loop using simple tools and a soldering iron.
Back in February 2019 we first posted about Radwave, an Android SDR App for RTL-SDR dongles. It has some interesting features not found in other Apps like the ability to easily zoom, pause and rewind the spectrum at any time.
The author has decided to make use of these spectrum browsing enhancements by providing access to full SETI (Search for Extraterrestrial Intelligence) spectrum data sets which can be browsed via the app for a small fee. From a post on our forums the author of Radwave writes:
This data comes from Breakthrough Listen. These datasets are quite large, and Radwave does all the bulk downloading, processing and hosting of the datasets, allowing you to easily navigate your way through the spectrum. If you find something cool, you can tag it and share it.
Currently there are three datasets available in the first bundle ($10 USD): Voyager 1 and two 'Oumuamua collections (surveys of the the first observed interstellar object in our solar system). The data is big, and is hosted in AWS. That gets pricey, so I'll be adding more collections to this first bundle as funding permits. If there are certain datasets you're interested in seeing, definitely let me know.
Over on YouTube William IU2EFA has been uploading multiple short "meteor scatter" videos. This involves using an RTL-SDR to briefly receive distant radio stations via the RF signal reflecting off the ionized trail left by meteors entering the atmosphere. However, in a similar fashion satellites orbiting the earth can also reflect distant radio stations.
In one of his latest videos William caught a train of Starlink satellites reflecting the signal from the Graves radar in France. To do this he uses a 10 element VHF Yagi, and an RTL-SDR running with HDSDR and SpectrumLab. In the video you can see and hear the change in frequency caused by the doppler shift.
Starlink is a SpaceX project aiming to bring ubiquitous satellite internet to the entire world. Currently 358 Starlink satellites are in orbit, and the end goal is to have 12000.
The built in equipment includes a GNSS receiver, orientation sensors, AIS receiver, 4G and WiFi, lightning EMI sensor and alarm, optional autopilot integration, rudder angle sensor, connections to boat instruments like wind, depth, speed, temperature, barometric and humidity sensors, an Iridium receiver, and finally an RTL-SDR for receiving weather fax, NavTex, satellite weather, AIS, RTL 433, morse code and more. It really is an "all-in-one" device.
His blog post explains in detail how each of the components work in the system, and in particular for the RTL-SDR he shows how you can use the boat computer to receive FM via GQRX, and NavTex via the Java based Frisnit Navtex decoder. Navtex is a marine radio service that transmits at 518 kHz or 490 kHz. It provides text data regarding weather forecasts, weather warnings, navigational information, and urgent maritime safety messages. For his antenna he writes that he uses a 10 kHz - 30 MHz Mini Whip antenna that he purchased on Aliexpress.
Over on YouTube ModernHam has uploaded a video showing how to create an APRS I-Gate and Digipeater with Baofeng and RTL-SDR. He also makes use of a Raspberry Pi as the computing module and an audio cable to connect the Baofeng to the audio jack of the Pi. The tutorial then consists of a walk through of the various software setup steps, and finally how to connect the Baofeng and RTL-SDR to the Pi.
If you weren't already aware, Automatic Packet Reporting System (APRS) is a digital VHF mode used in amateur radio. It allows for packets of data to be sent to receiving nodes over a local area via RF. Typical uses for it are vehicle tracking, weather station telemetry, text messages, announcements and other wireless device telemetry like high altitude balloons. An I-Gate is an internet connected node which receives local APRS RF signals and uploads them to the internet, to be seen on sites like aprs.fi. TX capable I-Gates may also broadcast to the local RF network messages from APRS transmitters on the other side of the world.
APRS I-Gate and Digipeater with Baofeng and RTL-SDR