Tagged: krakensdr

KrakenSDR: Finding Multiple GSM Base Station Transmit Towers with the Multi-VFO Feature

If you weren't already aware, KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding. KrakenSDR is in stock and can be purchased from CrowdSupply or Mouser. More information is also available on our website at krakenrf.com.

Last month we used the KrakenSDR to find the location of a low power FM transmitter. Now in this video we're using KrakenSDR to find the location of GSM base station transmit towers for four frequencies. We're also using the multi-vfo feature to capture the bearing data of these four frequencies simultaneously which can save us some search time.

Once we've found the first transmit tower, we already have some logged bearing data that can be used to help us find the second tower faster. Then the third and fourth towers are even faster to find due to even more data having already been collected.

Interestingly, it also turns out that the first frequency we search for is actually being used by another tower that we pass along the way back. The location of this tower was picked up on the drive back to the first tower. It's possible that these two towers which are a few kilometers apart are covering different areas with directional antennas.

Also note that the first two transmitter searches use the "auto-zoom" map camera feature, which will automatically zoom the screen to show both the vehicle and estimated transmitter location. The second half uses the standard free camera mode.

This is on a new build of the App which is currently in testing, so some things may look slightly different to the currently released version. The new app version will have some minor feature improvements.

KrakenSDR: Finding Multiple GSM Base Station Transmit Towers with the Multi-VFO Feature

 

Fox Hunting with the KrakenSDR

Over on his YouTube channel Mark Jessop has uploaded some dash cam footage showing him using a KrakenSDR and a custom LED display to hunt down three amateur radio transmitters during a fox-hunt.

An amateur radio fox-hunt is an activity where someone will hide a transmitter within a defined area, and it is up to the hunters to use radio direction finding equipment to find it. The KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding.

Mark uses a custom four element array on the roof of his car, which is connected to his KrakenSDR. Instead of the KrakenSDR app, Mark prefers to use his custom LED HUD to displays the bearings and signal power directly.

Some annotated and sped-up dash-cam footage captured during the July 2023 Amateur Radio Experimenters Group Fox-hunt. We run these monthly, and usually have three transmitters hidden around the Adelaide (South Australia) area.

I run a KrakenSDR with a custom-built 4-element antenna array mounted to the roof of my car. This gives me direction estimates to the target transmitter, at least when the signals are strong enough!

I've also build a heads-up-display which helps me safely make use of the KrakenSDR's output data while driving. The source code for this is here: https://github.com/darksidelemm/neopixel-doa-display

The display is shielded so it's not visible from outside the car - Red & Blue lights on your dashboard can give the wrong impression!

AREG Fox-hunt - 14th July 2023

KrakenSDR Low Power FM Transmitter Hunt

If you weren't already aware, KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding. KrakenSDR is in stock and can be purchased from CrowdSupply or Mouser. More information is also available on our website at krakenrf.com.

In this video we are using a KrakenSDR to hunt for the location of a low power FM transmitter (LPFM) station at 106.7 MHz. These low power FM transmitters are legal as unlicensed transmitters as long as they operate under certain restrictions, the main one being that they transmit at under 1 watt EIRP. LPFM stations are typically operated by local communities or niche radio stations.

Because they are unlicensed, there is no official record and their location doesn't show up in the radio spectrum management database. A requirement of LPFM is that the station broadcast the contact information of the owners regularly, but it can be difficult to locate non-compliant stations that don't do this. But the KrakenSDR makes finding them easy.

The array is 45cm in radius, which is about the maximum that my RAV4 car roof can fit. Some of the antennas sit on a slight curve on the roof, but this appears to have negligible effect. The spacing factor is about 0.19 (optimal is 0.5 - a much larger radius), but even 0.19 is sufficient to find the transmitter fairly easily.

KrakenSDR Low Power FM Transmitter Hunt

 
 

DragonOS: KrakenSDR and DF Aggregator Connected via a 1km WiFi Link

DragonOS is a ready to use Ubuntu Linux image that comes preinstalled with multiple SDR software packages including a tool called DF Aggregator, which can be used for radio direction finding with a device like our KrakenSDR.

In his latest video, Aaron, creator of DragonOS tests out a long range one kilometer WiFi link between a KrakenSDR, and his base station running DF Aggregator. The WiFi link is achieved by using a ALFA Network 802.11ah (900 MHz US) adapter. The remote KrakenSDR is running on a 'DragonDeck', which is a SteamDeck gaming console with DragonOS installed on it.

In the video Aaron shows that when he transmits with his handheld radio, the remote KrakenSDR is able to provide an accurate bearing towards the transmitter. At the end Aaron also briefly tests out automatic speech transcribing via WhisperCPP.

Aarons tests were run together with @VibesGoon who shows a few great pictures of his KrakenSDR setup on his Twitter Feed.

DragonOS FocalX 1km Remote Connect to KrakenSDR/SDR4Space w/ 802.11ah (hackRF, Halow-U, SteamDeck)

Aaron also shows another picture on his Twitter feed, which also shows the SteamDeck.

PySDR Guide on DOA & Beamforming

PySDR is a free online textbook created by Dr. Marc Lichtman which explains many digital signal processing (DSP) and software defined radio (SDR) concepts in a clear, concise and easy to understand way. The guide includes multiple images and animations, as well as Python code examples.

In a recent update, Dr. Lichtman has begun adding a new chapter on Direction of Arrival (DOA) and Beamforming which are core concepts for coherent radio direction finding devices like our KrakenSDR. As with the other chapters the guide is made easy to understand with many images and animations.

The introduction reads:

Direction-of-Arrival (DOA) within DSP/SDR refers to the process of using an array of antennas to estimate the DOA of one or more signals received by that array. Once we know the direction a signal of interest is arriving from, we can isolate it from other signals/interference/jamming.

It is just like isolating a signal in the frequency domain by filtering it, except we are now working in the spatial domain (you can certainly combine both!).

We typically refer to the antennas that make up an array as elements, and sometimes the array is called a “sensor” instead. These array elements are most often omnidirectional antennas, equally spaced in either a line or across two dimensions.

DOA is a subset of beamforming techniques, where as the receiver, we are trying to steer a beam (our receiver’s antenna beam) towards the direction of an emitter. We may also steer a beam blindly across a wide range (e.g., 0 to 360 degrees) to figure out what signals are being received and from what direction.

A visual example of what happens to two signals when the interelement spacing of a direction finding antenna array is reduced below half a wavelength.

Tech Minds: Testing an RTL-SDR Wideband Scanner with WebUI

Over on YouTube Matt from the Tech Minds YouTube channel has put up a video demonstrating an open source program released on GitHub called "RTL SDR Scanner", or "rtl-sdr-scanner-cpp". This program is compatible with RTL-SDR and HackRF software defined radios, and allows users to record multiple analogue FM audio channels within the active bandwidth simultaneously. 

To get a wider bandwidth, you can use a HackRF as your SDR, or you can also use multiple RTL-SDR dongles, or a device like the KrakenSDR which has multiple RTL-SDRs built into it. Alternatively, you can also have the software scan a much larger swath of bandwidth, however this could result in some transmissions being missed. 

The audio is recorded as a wav file, and can be accessed through a web UI. We note that currently only FM recordings are supported but AM may be supported in the future.

RTL SDR Scanner - FULL Bandwidth Recording With WEB UI

KrakenSDR Locates a Repeater Jammer in 1 Hour

Over on YouTubem channel NotaRubicon Productions has uploaded a video describing how a KrakenSDR was used to find the location of a person jamming a repeater site. Amateur radio enthusiasts can utilize VHF or UHF repeater towers, which receive signals from lower power handheld or other radios, and retransmit that signal at high power on a slightly different frequency over a much wider area. Unfortunately malicious people can jam these repeaters by transmitting at the same time as other users, effectively denying use of the repeater by legitimate users.

If you weren't already aware, KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding. We successfully crowd funded the device on Crowd Supply, and the device is currently available for sale on Crowd Supply, Mouser and direct from our website krakenrf.com.

In this video I read the story of how we caught the jammer that had been jamming our GMRS repeater for months, and how by using the KrakenSDR Radio Direction Finder (RF locator), we were at his house in 1 hour.

The KrakenSDR can track a signal being transmitted from 100Mhz to 1Ghz - so I can track ham repeater jammers, GMRS repeater jammers, ham-radio transmitters, GMRS radios - pretty much any transmitter with a signal strong enough for you to receive.

How The KrakenSDR Located Our Repeater Jammer In 1 Hour. Overview of the KrakenRF Inc. RF Locator

KrakenSDR now in stock in our shop

As per our previous post we wanted to note that our direct sales KrakenSDR shop is now up and running with immediate shipping available. There is only a limited number of KrakenSDRs and antenna sets that we can sell direct to customers. After this stock is depleted all sales will need to go through Crowd Supply again. Regardless, both Crowd Supply and our direct sales shop are in stock right now.

If you weren't already aware, KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding and passive radar. We successfully crowd funded the device on Crowd Supply.  

KrakenSDR Shop now open
KrakenSDR Shop now open