A new UK designed and manufactured upconverter that goes by the name SDR(X) has recently become available for purchase. This upconverter connects to a RTL-SDR dongle and allows it to receive from 100 kHz up till 1850 MHz. Some of its features include:
Four user selectable HF pre-filters (0-2, 2-6, 6-11 and 11 to 30MHz) or single 0-30MHz pre-filter.
Band pass filter after mixer and band pass filter after Oscillator
User selectable MMIC 18db amplifier external to RTL chip set (lower noise level, than RTL chip and compensates for pre-filters).
User selectable HF and VHF/UHF mode (HF 0-30MHz, VHF/UHF mode 24MHz to 1850MHz).
Microchip PIC controller for above.
Diode protection on RF input.
The board comes as a prebuilt kit which is currently selling for 79.95 GBP which includes an RTL-SDR dongle. The device also comes with complete documentation. The SDR(X) can be purchased from 6v6.co.uk.
Over on YouTube user w2aew has uploaded a tutorial video that clearly explains the theory behind upconverters. Upconverters are commonly used with the RTL-SDR to receive the HF (0 – 30 MHz) bands. In the video he shows how to make a simple homemade double-balanced diode ring mixer for the RTL-SDR and shows its performance in HDSDR.
#174: Using a mixer to listen to HF, shortwave, ham, etc. on RTL-SDR dongle
The second plugin is a Digital Code Squelch (DCS) decoder plugin. The plugin will display the DCS codes that are transmitted with the signal and will display all possible compatible codes. DCS is a squelching system similar to CTCSS which allows for radio user sharing by ensuring that radio users are not bothered by communications not intended for them. The DCS Decoder plugin can be downloaded from http://www.rtl-sdr.ru/page/novyj-plagin-dcs-decoder (note page in Russian).
Digital Code Squelch (DCS) Decoder Plugin for SDR#
Over on the Reddit discussion boards user gat3way has posted about his newly released software project called swscan. Swscan is a Linux console based program that can be used to scan and listen to shortwave broadcast stations. It has a built in database of shortwave station frequencies as well as their broadcast schedules and it will even show you the stations power level and distance you are from the transmitter. Swscan is based on GNU Radio 3.7, so you will need to have that installed first.
As shortwave stations exist at frequencies below the normal tuning range of the RTL-SDR, you will need an upconverter or be using the latest R820T experimental driver which can tune down to around 1 MHz.
Over on the Osmocom mailing list, Oliver Jowett an RTL-SDR experimenter has posted about his new experimental driver for the R820T RTL-SDR which extends the tunable range down to around 13 and up to 1864 MHz (previously 24 – 1766 MHz). Oliver writes
You can get these changes from https://github.com/mutability/rtl-sdr/ (you’ll need to build from source yourself). There should be no application changes needed, just tune as normal. (gqrx needs the “no limits” option turned on) These changes work by limiting the tuner to a range of frequencies that it can reliably tune to, then allowing tuning beyond those bounds by making the 2832’s downconverter do the final bit of tuning. This can add up to 14.4MHz to each end of the range. Also, the tuner is switched to low-side mixing at the top of the range which gives a bit more range there. The practical range is limited by the width of the IF filter and aliasing effects at the extreme edges of the downconverter’s range. I’ve been able to pick up broadcast AM and amateur CW/SSB down to around 15.5MHz without too much trouble. I’d be interested to know how this works for others. Also.. these changes are likely to have broken offset tuning, direct sampling mods, and tuners other than the R820T, as it touches all those areas but I only have an unmodified R820T to test against. If you have different hardware and are willing to spend some time testing then please let me know. I expect that the range of the other tuners can be extended in the same way with not much trouble.
Over on the Reddit RTL-SDR discussion board there has been talk about this patch. Most users are reporting that it works well down to around 15 MHz, but some people are reporting that they have been able to receive signals down to around 4 MHz. Testers also report that this modified driver works much better than the no-hardware direct sampling mod patch released a few months ago.
A new HF upconverter designed for the RTL-SDR has gone up on ttrftech’s Japanese language blog (use Google Translate). The upconverter is called the ‘SC-HFCONV-100’ and comes with 100 MHz oscillator, SMA connectors, USB mini-B power.
A few months ago we posted about a Chinese individual (BA5SBA) who had begun selling RTL-SDR dongle kits for receiving HF frequencies. Back then it wasn’t entirely clear what these kits were or where they came from. Now over on Reddit, poster SidJenkins has bought one of these kits and assembled it. He has uploaded images of the construction which can be found here and the Reddit discussion can be found here. The kit is essentially an RTL-SDR extension PCB board that aids in building a direct sampling RTL-SDR with good performance by including filters and impedance matching.
SidJenkins notes that the kit came with no instructions, so he used this thread in Chinese (use Google translate) to help put the kit together.
Over on YouTube user crookedninja5 has uploaded a video showing what he calls the “Easy HF dongle mod”. The mod involves soldering a wire from Pin 1 on the RTL2832U chip to the static protection diode near the antenna input. At the same time he also uses the modified RTL-SDR dll file for SDR# which enables the “no hardware mod” direct sampling mode.
Using this mod he is able to get decent coverage of 0 – 14.4 MHz.
