Category: Amateur Radio

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

SoftRock Lite II Build and Test Tutorial Video

The SoftRock Lite II is a (now fairly old) soundcard based software defined radio kitset that is capable of receiving on the HF bands. Over on YouTube user w2aew has uploaded a video showing the entire kitset build process for the SoftRock Lite II SDR radio. He also goes over the circuit blocks explaining their function and how they work.

This is an excellent video if you are interested in learning more about the components and circuits used in some SDRs.

#148: Software Defined Radio kit | Tutorial | Build | Test | Softrock Lite II

RTL-SDR HF Preselector Project

Over on YouTube user Theo Faber has uploaded a video showing his adjustable multiband HF preselector project for his RTL-SDR dongle. The preselector covers the entire HF band. Theo designed and built his own homemade upconverter for this project as well.

Preselectors on the RTL-SDR can vastly improve reception quality. Without preselection, noise and strong images of other nearby stations can cause strong interference.

My project ‘pre selector’ for wideband radios and in particular the popular tv-sticks than can be used for SDR reception. The sticks are very cheap and the software free available on the internet. SDR Sharp in this case, is operating stable under XP and W7. Sticks are sensitive, however the input level can only vary +- 20dB. The sticks are easely overloaded and will produce cross and intermediation. So you need in front of the stick / converter band pass or tunable filters. Hopefully this inspired you to build your own set of filters, to fully benefit from the perfect performing of this affordable SDR.
for more info contact me on: t.faber87__AT__upcmail.nl
kind regards and 73’s

SDR RTL dongle and pre selector with HF converter

Receiving Kicksat Telemetry with the RTL-SDR

Recently a bunch of amateur radio nano-satellites known as ‘Kicksats‘ were launched on the latest SpaceX rocket. So far the Kicksat carrier has been successfully deployed, which is essentially the box containing the nano-satellites. On May 4, the nano-satellites known as ‘sprites’ are due to be deployed from the carrier.

Both the carrier and Kicksat sprites have telemetry signals which are receivable with the RTL-SDR. As the sprites transmit using only 10mW of power, a high gain Yagi antenna and an LNA are required to receive their signals.

Over on his blog, Dolske has been trying to receive and record the Kicksat carrier using his RTL-SDR. He was able to capture a telemetry packet at 437.505 MHz using SDR#. He then tried to use QTMM AFSK1200 to decode the packet, but has been unsuccessful so far probably due to the weak signal he received.

Kicksat 'nano' satellite sprite.
Kicksat ‘nano’ satellite sprite.

Softrock Ensemble II vs the RTL-SDR + Upconverter on Shortwave

Over on YouTube user mutezone has posted a video comparing the RTL-SDR with upconverter against a Softrock Ensemble II software defined radio. The Softrock Ensemble II is an SDR dedicated to the HF frequencies and is thus expected to have better performance for that purpose. Mutezone writes

A performance between the Softrock Ensemble II vs the RTL-SDR (R820T) on shortwave. Here we are trying to see which one is best at receiving AM broadcasters. Both SDRs were using the same longwire antenna connected to an ATU (Antenna Tuning Unit).

Although I know this comparison is somewhat unfair, since the RTL-SDR is not meant for shortwave & the Softrock is, it is to show that there is a difference in performance, even though the RTL-SDR has a much wider frequency range & cannot be beaten when it comes to value for money. My opinion is that if you want an SDR that should deliver on HF / Shortwave performance, then go for a dedicated one like the Softrock, Afedri, SDR-IQ or any others that do the same job on the market. Even when using a decent HF Upconverter, the RTL-SDR will still not match the performance of more upmarket HF SDRs.