New SDR# Plugin: Multiple VFO’s

Over on the blog the programmer of many well used SDR# plugins has released a new one which allows you to have up to two extra VFO’s in SDR# (note in Russian, use Google Translate). In order words this means that you can now listen to up to three signals simultaneously if they are in the same swath of live bandwidth. Previously on Windows only the SDR-Radio V2 software was capable of doing multiple VFO’s.

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.

Extra VFO's Plugin
Extra VFO’s Plugin

Digital Ding Dong Ditch – Hacking wireless doorbells with Arduino and RTL-SDR

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.

If you don’t like video explanations, Samy has also done a write up of the same material on his website.

Digital Ding Dong Ditch – hacking wireless doorbells with Arduino and RTL-SDR

New Products from Nooelec: Cheaper E4000 Dongles and a 9:1 Balun

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.

E4000 Dongle from Nooelec
E4000 Dongle from Nooelec

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.

Nooelec 9:1 Balun
Nooelec 9:1 Balun

SDR on TV: Using SDR to Break into Homes with Wireless Alarms

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

New RTL-SDR + Upconverter Available

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.

BA5SBA’s new upconverter can be found for sale on Ebay for around $80 USD.

We also posted previously about BA5SBA’s direct sampling kit here.

RTL-SDR + Upconverter in a box by BA5SBA
RTL-SDR + Upconverter in a box by BA5SBA
Example of reception
Example of reception RTL-SDR Giveaway

The guys at the 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

Twelve (12)
NESDR Mini 2 SDR sets
$25.95 value and NooElec Giveaway and NooElec Giveaway

Receiving WSPR with the RTL-SDR

Recently 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.

Some Received WSPR Locations
Some Received WSPR Locations
WSPR Report Information Including Distance
WSPR Report Information
The WSPR Software
The WSPR Software

Listening to FreeDV Digital Speech with an RTL-SDR

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.


Characterizing the SWR of an Antenna with a Noise Source and an RTL-SDR

In our last post Adam 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

Characterizing RF Filters with a Noise Source and RTL-SDR Dongle

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.

The noise source can be built from a simple diode based circuit as shown in a previous post, or if you have the Ham-it-up upconverter you can buy the parts for the noise generator part of the circuit.

In his video he shows the frequency response of a 145 MHz helix filter, a coax notch filter and a 1090 MHz home brew bandpass filter.

Characterize filters with the DVB-T SDR (part 1)

Characterize filters with the DVB-T SDR dongle (part 2)

More filters and DVB-T dongle