Listening to multiple frequencies simultaneously has many uses including the ability to now monitor multiple ACARS, AIS, pager and other data frequencies at the same time. However, as of yet it seems that the ability to output to other audio devices such as a virtual audio cable is not yet implemented.
Over on YouTube user Samy Kamkar has uploaded a video showing how he was able to use an RTL-SDR to copy his friends wireless doorbell signal and prank him by replaying it using an Arduino and 433 MHz transmitter. His video goes through the entire reverse engineering process he used from recording the wireless doorbell signal with the RTL-SDR, to analyzing and understanding the signal and finally to programming the Arduino with the code to replicate the doorbell signal.
The online store Nooelec has recently started selling two new RTL-SDR related products.
The first product is a lower cost RTL-SDR dongle with the E4000 tuner (ebay). The E4000 tuner was one of the original tuner chips used in RTL-SDR dongles when they were first discovered. Unfortunately Elonics, the company that owned the rights to the chip went under and the production of E4000 chips stopped, making them rare and expensive. The E4000 tuner has a tuning range of approximately 55 MHz – 2300 MHz, compared to the R820T tuner which has a range of around 24 – 1766 MHz. The cheaper R820T is better in most cases, but if you need the higher frequencies the E4000 may be an option. The new E4000 dongle is currently selling for around $50 USD, compared to the other E4000 models which went for around $100 USD.
They have also begun selling a low cost 9:1 balun for about $10 USD (ebay) which can be used with a long wire (or random wire) antenna when receiving HF on the RTL-SDR with an upconverter. The impedance of a long wire antenna is approximately 450 Ohms (very approximate, impedance varies with frequency and length). A 9:1 balun allows a match with a 50 Ohm receiver, which is close enough to the 75 Ohm input of the RTL-SDR.
Earlier this year the American TV show Good Morning America featured a segment on software defined radios being used to break into houses with wireless alarm sensors. The story is based on a Defcon 2014 paper “Home Insecurity: No Alarms, False Alarms, and SIGINT” by Logan Lamb. In the TV segment Logan shows how he uses a USRP software defined radio to send a false alarm signal, jam a wireless sensor and finally to record sensor activation data from the alarm system.
Although Logan used a USRP, the same attack could be done with the cheaper HackRF.
SDR HackRf: Home Insecurity: No Alarms, False Alarms, and SIGINT
BA5SBA, the creator of the Chinese direct sampling kit (and fully assembled version) recently wrote in to let us know about a product that he is now building. His new product is a fully assembled RTL-SDR + Upconverter. The upconverter design uses a DBM balanced ring mixer design which he writes makes less noise and has greater dynamic range. He also writes that compared to direct sampling the upconverter model should have greater sensitivity as it allows use of the R820T LNA. His design uses a 40 MHz local oscillator, comes with increased RF input protection and comes in an aluminium case.
The guys at the AmateurRadio.com blog have teamed up with Nooelec to bring everyone a worldwide competition giveaway of 20 RTL-SDR prizes. The top prizes include the rare E4000 chip tuners, ham-it-up upconverters, adapters and aluminium enclosures while the regular prizes include an R820T2 RTL-SDR set.
To enter the competition all you need to do is leave a comment on their competition post. The competition is open for one week from 11 December 2014 to 18 December 2014. The complete list of prizes are quoted below.
Three (3) Complete NESDR XTR HF SDR packages including:
NESDR XTR SDR Set (E4000 chip)
Ham It Up upconverter
Upconverter Enclosure (silver)
Male MCX to male SMA pigtail (SDR cable)
Male SMA to female BNC adapter (antenna adapter) Estimated $129.95 value
Five (5) Complete NESDR Mini 2 HF packages including:
NESDR Mini 2 SDR set
Ham It Up upconverter
NESDR Mini 2 enclosure (silver)
Upconverter enclosure (silver)
Male MCX to male SMA pigtail (SDR cable)
Male SMA to female BNC adapter (antenna adapter) $111.95 value
Recently RTL-SDR.com reader DE8MSH wrote in to let us know about his experiments with receiving WSPR with his RTL-SDR. WSPR is an acronym for “weak signal propagation reporter” and is a software program and RF protocol designed for very weak signal radio communications between ham radio users. With less than 5W of transmitting power, a WSPR signal could potentially be copied all over the world.
To receive WSPR, DE8MSH used a direct sampling modified RTL-SDR dongle together with a 9:1 unun, 10m RG58 coax cable from RTL-SDR to unun and a 12m wire antenna outside his house. Then by using SDR# together with the WSPR software he is able to copy signals from all over Europe and Canada/USA from his home in Germany.
Over on YouTube user BSoD Badgers has uploaded a video showing his reception of FreeDV digital speech at 14 MHz. He uses SDR# combined with the FreeDV software to decode the signal.
FreeDV is a open source software application that allows digital speech to be sent at HF frequencies in a 1.25 kHz wide signal. The same software can be used on the receiving end to decode the signal into speech.
In our last postAdam Alicajic showed us on YouTube how to determine the frequency response of an RF filter using just a wideband noise source an LNA and an RTL-SDR dongle.
In his latest video Adam shows how the SWR of an antenna can be measured using almost the same low cost equipment. One additional piece of hardware required to measure the SWR is a directional coupler which can be bought on Ebay for about $10 USD.
SWR stands for “standing wave ratio” and is a measure that can be used to tune an antenna for a particular frequency. The closer the SWR is to 1:1 at the designed antenna frequency, the better the antenna will receive (and transmit).
In his video Adam shows how he measures the SWR of an ADS-B antenna which he has built and is selling. His results show that the antenna has an SWR of 1:1.02 at 1090 MHz which is quite good.
DIY Characterize the antenna Retrurn Loss / SWR with the DVB-T SDR
Over on YouTube RTL-SDR experimenter Adam Alicajic has uploaded a video showing how it is possible to use the RTL-SDR as a tool to measure the frequency response of an RF filter. To do this he uses a noise source circuit which produces wide band white noise connected to an LNA4ALL, connected to the RF filter and finally connected to the RTL-SDR. Then using the Touchstone spectrum analyzer software he does a 300 MHz bandwidth sweep over a section of the spectrum which shows the response of the filter.