Category: Amateur Radio

SDR(X): New Upconverter for the RTL-SDR

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.

Image of the SDR(X)
Image of the SDR(X)

Using a Mixer to Listen to HF on a RTL-SDR Dongle

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

New Japanese HF Upconverter for the RTL-SDR

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.

Currently the upconverter is only available for sale on the Japanese Amazon store, but it is possible to still order it through the jzool-agent Japanese shopping service.

Japanese HF Upconverter
Japanese HF Upconverter

Assembling the Chinese RTL-SDR Direct Sampling Kit

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.

Chinese RTL-SDR Kit
Chinese RTL-SDR Kit

Receiving a VLF Transmission using a PC Soundcard

Over on YouTube user Alex swl has uploaded a video showing his reception of a Very Low Frequency (VLF) radio signal using a laptop running SDRSharp and a Chirio Mini Whip antenna connected directly to the laptop’s sound card input.

Every year on Alexanderson Day (this year on 29/06/2014) and some other days the Varberg VLF Radio Station in Sweden transmits a morse code message using a 1.9 km (1.2 mile) horizontal wire antenna at 17.2 kHz with callsign SAQ. Because the transmission frequency is so low, a standard PC soundcard can be used to directly receive the signal.

Alex swl was able to receive this signal in Italy.

Using Xastir with the RTL-SDR

Xastir is a Linux based program that is used for plotting Automatic Packet Reporting System (APRS) data on a map. APRS is is type of packet radio system used by ham radio for real time local area digital communications. It is often used for sending messages, plotting positions on a map or providing weather station data.

Over on his blog, KJ6VVZ’s has uploaded a post showing how he was able to get the RTL-SDR working with Xastir. He uses rtl_fm piped into MultimonNG for the APRS decoding and then sends the decoded APRS information to Xastir via a FIFO buffer.

Xastir Message Log
Xastir Message Log

KN0CK HF Upconverting and Direct Sampling RTL-SDR Receiver Store

In previous posts we have featured Marty KN0CK’s popular modified RTL-SDR dongles which have either a miniature built in high quality HF upconverter with amplifier and filter, or an amplified and filtered direct sampling modification applied to them. With these modified dongles you can receive the HF frequencies from 0.5 MHz to 54 MHz. These kits were previously available for sale on a webstore, however that store has since closed down.

Fortunately, Marty’s modified RTL-SDR dongles are still available at http://www.kn0ck.com/HF_SDR/. The HF upconverting dongle can be bought for $75 and the direct sampling dongle at $60. The store page also shows example videos of the performance you can expect.

KN0CK HF Upconverting RTL-SDR Modification
KN0CK HF Upconverting RTL-SDR Modification
KN0CK HF DIrect Sampling RTL-SDR Modification
KN0CK HF DIrect Sampling RTL-SDR Modification

YouTube Review of the DX Patrol 100 kHz to 2 GHz SDR Receiver

The DX Patrol 100 kHz to 2 GHz SDR receiver appears to be a custom built RTL-SDR with upconverter built in. It is made by CT1FFU who is also known to be a good manufacturer of upconverters for the RTL-SDR. The DX Patrol SDR can be bought for 79 Euros at CT1FFU’s website. It’s features are as follows:

  • Ultra Wide-band Coverage SDR Receiver
  • Full coverage reception form 100KHz to 2GHz SDR
  • Independent antenna inputs for Shortwave and VHF
  • USB computer connection ( mini usb)
  • Very High dynamic range receiver
  • Low noise pin-diode band switch
  • Accurate and efficient band filters
  • Very clean audio reception
  • SMA golden antenna connectors
  • LED power and band indication
  • 40MHz local oscillator for HF conversion
  • DBM balance diode ring mixer
  • Small size board
  • Freeware software
  • Up to 3.2 M Sample rate.
Ultra Wide band SDR Receiver 100KHz to 2GHz
Ultra Wide band DX Patrol SDR Receiver 100KHz to 2GHz

We aren’t sure how this compares to a standard RTL-SDR with conventional upconverter, or direct sampling mode and we also aren’t sure about the truthfulness to their very high dynamic range claims as the RTL-SDR is known to have dynamic range that isn’t what could be called very high (8 bits ~ 50 dB).

Over on YouTube user OfficialSWLchannel has uploaded a video review. OfficialSWLchannel gives a generally positive review of the hardware.

DX Patrol SDR Receiver Review and Observations