Salamandra is a tool to detect and locate spy microphones in closed environments. It find microphones based on the strength of the signal sent by the microphone and the amount of noise and overlapped frequencies. Based on the generated noise it can estimate how close or far away you are from the mic.
Salamandra can either be used in live mode, or can use data recorded from rtl_power. It seems that the software simply attempts to detect peaks in the spectrum that look like analog audio, and print out their frequencies.
We’ve also seen this somewhat related piece of software called rtlsdr-wwb-scanner which can be used with an RTL-SDR to scan for microphones as well. However, this software is mostly intended to be used with the Shure Wireless Workbench which is a professional program for managing multiple microphones used in conferences, theatre performance, concerts etc.
Apologies for the long out of stock period, we sold out of our remaining Amazon US stock almost immediately a few weeks ago due to a large Reddit thread which popularized the Reddit /r/rtlsdr forums (a big welcome to any new RTL-SDR users!). Amazon is currently processing the new stock and it should be ready to ship out in a few days.
We also have a new antenna set in the works which should be ready for purchase in a few weeks. This antenna set is essentially a custom modified TV dipole with mounting kit. The kit will contain:
1x Telescopic Dipole Antenna base with 20cm RG174 cable
2x removable 22cm to 1M telescopic antennas
2x removable 5cm to 13cm telescopic antennas
1x 3M SMA RG174 extension cable
1x suction cup window mount
1x bendy tripod mount
Antenna Base
The telescopic antennas mount onto the antenna base via a screw, so they can easily be removed and interchanged between the large and small ones, or packed away for storage.
The dipole antenna base attaches to the suction cup or bendy tripod mounts using a 1/4″ camera screw. So any cheap camera mounting accessories like clamps, tripods etc can be used to mount the dipole as well.
The coax cable on the base also has a ferrite core choke on it to help decouple the feedline from the antenna, and there is a 100kOhm bleed resistor added to reduce static discharge.
Mounts
The included suction cup mount allows you to mount the dipole on a window (ideally outside) and orient it into a vertical, horizontal or V-Dipole position. The bendy tripod allows you to use the antenna on your desk, folded over a door, on a tree branch, pole, or anywhere that the tripod legs can be wrapped around.
Usage
The biggest problem that new RTL-SDR users face is the antenna. Most are starting off with a mag mount whip, and have no way to mount them outside where they should be for better reception. Keeping them inside can cause poor reception and increased pickup of local interference from electronics. Our dipole with the mounts aims to solve this problem.
Using a dipole generally results in better reception than with a mag mount whip, and also allows for easier outdoor mounting. The 3M coax extension cable allows you to get the antenna at least to a window in your room.
Note that although we recommend using the antenna outside, please remember to take the antenna back inside when not in use to avoid lightning/ESD/weathering problems. It is not designed for permanent outdoor mounting and please remember that any permanently mounted outdoor antenna should have good grounding to protect your radio against ESD and lightning.
For general use we recommend using the dipole in the vertical orientation as most signals are vertically polarized. The dipole can also be used in a V-Dipole configuration for excellent VHF satellite reception, such as for NOAA/Meteor weather satellites. Just extend the telescopic dipoles to be as close as possible to resonant at the frequency of interest using this calculator. Getting the length perfect is not critical, and actually using any length will still receive something.
Apart from NOAA we’ve also tested the dipole with L-band satellites. Together with an LNA and the smaller telescopic antennas it’s possible to receive Iridium and Inmarsat signals. Reception is not as good as a patch antenna, but you can still get the stronger AERO and Iridium signals quite easily. If you add a reflector made out of a small cookie tin the signals can be boosted further, and this is enough to receive the weaker STD-C and Outernet signals.
Eventually this dipole set will replace the mag mount antenna bundled with the dongles currently. Target price is between $9.95 – $14.95 for the antenna set by itself, and $25.95 for the dongle + antenna set. We expect the antenna set to be ready for shipping in 2-3 weeks, and about 3-4 weeks for the dongle + antenna set. More details and usage examples will be shown nearer to the release.
If you are in Europe you can also make use of the Graves radar simply by tuning to its frequency of 143.050 MHz and listening for reflections of its signal bouncing off things like meteors, planes and spacecraft. Since Graves points its signal upwards, it’s unlikely that you’ll directly receive the signal straight from the antenna, instead you’ll only see the reflections from objects.
DK8OK also explains in his post how you can use SDR-Console V3 to create a level diagram which shows power vs time, allowing you to count reflections and visualize the response of the reflection.
Any SDR that can tune to VHF frequencies such an an RTL-SDR can be used for monitoring reflections like this. If you aren’t in Europe you might consider looking for distant strong transmitters such as for TV/FM which you could also monitor for reflections.
Graves reflection of a meteor trail visualized in SDR-Console V3.
Erwin Rauh, DL1FY: Charly25 – SDR Transceiver Project – Community Development (Link)
Črt Valentinčič, S56GYC, Red Pitaya: HamLab (Link)
Evariste Courjaud, F5OEO: Rpitx : Raspberry Pi SDR transmitter for the masses
Low cost RTL-SDR democratize access to SDR reception, but is there an equivalent low cost solution for transmission : Rpitx is a software running on Raspberry Pi which use only GPIO to transmit HF. This presentation describes how to use it as a SDR sink but also describes details of how it is implemented using PLL available on the Raspberry Pi board. Warnings and limits of this simple SDR are also provided before going “on air”. Last paragraph shows what are potential evolutions of this system : low cost DAC and third party software integration.
Evariste Courjaud, F5OEO: Rpitx : Raspberry Pi SDR transmitter for the masses
Stefan Scholl, DC9ST: Introduction and Experiments on Transmitter Localization with TDOA
Time-Difference-of-Arrival (TDOA) is a well-known technique to localize transmitters using several distributed receivers. A TDOA system measures the arrival time of the received signal at the different receivers and calculates the transmitter’s position from the delays. The talk first introduces the basics of TDOA localization. It shows how to measure signal delay with correlation and how to determine the position using multilateration. It also covers further aspects and challenges, like the impact of signal bandwidth and errors in delay measurement, receiver placement and synchronization as well as the requirements on the network infrastructure. Furthermore, an experimental TDOA system consisting of three receivers is presented, that has been setup to localize signals in the city of Kaiserslautern, Germany. The three receivers are simple low-cost devices, each built from a Raspberry PI and a RTL/DVB-USB-Stick. They are connected via internet to a master PC, which performs the complete signal processing. The results demonstrate, that even with a simple system and non-ideal receiver placement, localization works remarkably well.
Stefan Scholl, DC9ST: Introduction and Experiments on Transmitter Localization with TDOA
Frank Riedel, DJ3FR: The HackRF One as a Signal Generator
The usability and performance of the HackRF One SDR experimental platform as a signal generator up to 6 GHz is examined by means of an HPIB driven measurement system. The effective circuit of the HackRF One used in the CW TX mode is described and its components are linked to the parameters of the command line tool ‘hackrf_transfer’. The frequency accuracy of the HackRF One is measured against a frequency standard, output signal levels and spurious emissions are determined using a spectrum analyzer.
Frank Riedel, DJ3FR: The HackRF One as a Signal Generator
Bitcoin is the worlds first and most popular digital currency. It is steadily gaining in value and popularity and is already accepted in many online stores as a payment method. In order to use Bitcoin you first need to download a large database file called a ‘blockchain’, which is currently at about 152 GB in size (size data obtained here). The blockchain is essentially a public ledger of every single Bitcoin transaction that has ever been made. The Bitcoin software that you install initially downloads the entire blockchain and then constantly downloads updates to the blockchain, allowing you to see and receive new payments.
Blockstream is a digital currency technology innovator who have recently announced their “Blockstream satellite” service. The purpose of the satellite is to broadcast the Bitcoin blockchain to everyone in the world via satellite RF signals, so that even in areas without an internet connection the blockchain can be received. Also, one problem with Bitcoin is that in the course of a month the software can download over 8.7 GB of new blockchain data, and there is also the initial 152 GB download (although apparently at the moment only new blocks are transmitted). The satellite download service appears to be free, so people with heavily metered or slow connections (e.g. 3G mobile which is the most common internet connection in the third world/rural) can benefit from this service as well.
The service appears to be somewhat similar to the first iteration of the Outernet project in that data is broadcast down to earth from satellites and an R820T RTL-SDR is used to receive it. The blockstream satellite uses signals in the Ku band which is between 11.7 to 12.7 GHz. An LNB is required to bring those frequencies back down into a range receivable by the RTL-SDR, and a dish antenna is required as well. They recommend a dish size of at least 45 cm in diameter. The signal is broadcast from already existing satellites (like Outernet they are renting bandwidth on existing satellites) and already 2/3 of the earth is covered. The software is based on a GNU Radio program, and can be modified to support any SDR that is compatible with GNU Radio. They write that the whole setup should cost less that $100 USD to purchase and set up.
To set it up you just need to mount your satellite antenna and point it towards the satellite broadcasting the signal in your area, connect up your LNB and RTL-SDR and then run the software on your PC that has GNU Radio installed.
More details can be found on the Blockstream Satellite website, and technical details about the software and hardware required can be found on their GitHub page.
How the Blockchain satellite works (From blockstream.com/satellite/howitworks/)
Some may wonder what’s the point if you can’t transmit to the service to make payments with it. Over on this Bitcoin Reddit thread user “ideit” explains why it’s still useful in this nice quote.
You sell goats in a small village. A customer wants to buy a goat, but you have no banks so people have put their money into bitcoin. Your customer goes to the village center which has a few computers hooked up to the internet. He sends you payment then comes to get his goat. You don’t have internet near your goat farm, but you’re connected to the satellite so you can see he sent you payment and you give him his goat.
Or, you live in an area that caps your bandwidth. You want to run a full node, but downloading blocks eats away at your cap. Connecting to a satellite reduces your bandwidth usage.
Or, you’re using an air gapped laptop to sign transactions from your wallet for security reasons. You can now connect that laptop to the satellites so your laptop can generate its own transactions without connecting to the internet.
Or, your internet connection is terrible. You can usually broadcast transactions since they’re small, but downloading blocks and staying in sync with the blockchain is literally impossible. Connect to a satellite and now it’s simple.
In the post he shows how to make a cheap quarter wave ground plane antenna for ADS-B and then goes on to show the installation steps required to get PiAware running on the C.H.I.P. He also mentions his Power over Ethernet (PoE) setup which allows him to power the RTL-SDR and C.H.I.P via an Ethernet cable which also provides the network connection. A power setup like this is great for getting your receiver in a remote location without coax cable losses, although you do need to watch the voltage drop on the Ethernet cable.
The C.H.I.P is a cheap $9 single board computer that had a successful Kickstarter back in 2015. Unfortunately since the Kickstarter it has been almost impossible to obtain a unit (we’ve been waiting over a year). Hopefully more will ship soon.
Last year KD0CQ discovered that the SUP-2400 is a cheap $5 – $10 DirecTV (US satellite TV) module which can be hand modded into a downconverter for the RTL-SDR. A downconverter allows you to listen to frequencies above the maximum frequency range of the RTL-SDR by converting frequencies down into a range receivable by the RTL-SDR (or of course any other SDR). The modified SUP-2400 allows to you listen up to just over 4 GHz.
The SUP-2400 modification is moderately involved and requires soldering and desoldering SMD pieces, so this product is great for anyone who just wants a cheap and low cost downconverter which is ready to go. And at $25 USD it’s still very good value. Shipping within the USA is $7.75, and internationally it is about $13.50.
Manuel a.k.a ‘Tysonpower’ has been using his RTL-SDR (and his Baofeng) to listen in on ARISS contacts from the International Space Station (ISS). ARISS stands for Amateur Radio on the ISS, and is a program often used by schools to allow students to contact and ask questions to astronauts on the ISS with a ham radio. It is possible for anyone to listen in on the downlink (astronaut speech) if the ISS is over your location while transmitting. The uplink however may not be able to be heard as the signal is directed upwards towards the station.
For his first try he used a Baofeng (cheap Chinese handheld) and a DIY Carbon Yagi. For the second contact he used his RTL-SDR V3, an FM Trap and an LNA4ALL on a V-Dipole antenna placed on the roof of his car. With this set up he was able to receive the downlink transmissions from 1.6 degrees to 1.3 degrees elevation.
Paolo Nespoli ARISS Kontakt mit VCP-Bundeszeltplatz - 1. August 2017
Paolo Nespoli ARISS Kontakt mit FOFM / Moon Day - 5. August 2017
