Category: HF

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.

Aircraft Messages with HFDL, MultiPSK and the RTL-SDR

Over on YouTube user k2nccvids has posted two videos showing how he was able to decode High Frequency Data Link (HFDL) packets using the RTL-SDR, Ham-it-up upconverter, MultiPSK and HFDL Display. HFDL is a service similar to ACARS but sent over HF frequencies. It is used to sent short messages to and from aircraft and ground stations.

In the first video k2nccvids uses MultiPSK with the RTL-SDR directly and also uses the add on software HFDL Display to more clearly view received HFDL packets. In the second video he uses SDR-CONSOLEv2 to monitor three HFDL frequencies simultaneously, with MultiPSK and HFDL Display still being used for decoding and display.


Direct Sampling Mode with No Hardware Modifcations

Update: There is now a newer driver that allows HF tuning without hardware mods via a different mechanism. The new mod seems to work better than this one. Read about it at https://www.rtl-sdr.com/new-experimental-r820t-rtl-sdr-driver-tunes-13-mhz-lower/.

Over on the Reddit RTL-SDR forums user Jengal has posted a modified RTLSDR.dll dll file for SDR# which allows the direct sampling mode to be used on the R820T without the need for any hardware modifications. The modified dll is compiled from keenerds experimental branch of the RTL-SDR driver, which uses code for the no hardware mod written by tejeez. The no hardware direct sampling code was inspired by Anonofish’s discovery where he found that the E4000 based RTL-SDR could tune to AM radio without the need for the direct sampling mod (though this appears to be now patched in the newer rtlsdr drivers).

The direct sampling mod is a hardware modification to the RTL-SDR which allows it to receive HF frequencies between 0-14.4 MHz without the need for an upconverter. It works by connecting an antenna directly to the RTL2832U chip, thus bypassing the tuner. Teejez’s modification tells the RTL-SDR to bypass the tuner in software, allowing antennas to be connected to the normal antenna port. HF reception with the experimental driver is very poor in comparison to the direct sampling hardware mod or an upconverter, but even so Jengal was able to receive AM Radio, an SSB ham radio signal and an HF weather report with a simple longwire antenna.

To use the modified dll, simply download it from this link, rename it to rtlsdr.dll, and replace the original rtlsdr.dll in the SDR# folder. Then connect an HF antenna to the normal antenna port and in SDR# tune to a frequency between 0-14.4 MHz. Next turn ON the RTL AGC option in the configure menu. Jengal replaced the function of the RTL AGC option with the direct sampling mod. He found that best reception occurred when he set the gain to 48 dB.

No Hardware Mod Direct Sampling in SDR# Receiving AM Radio
No Hardware Mod Direct Sampling in SDR# Receiving AM Radio

Receiving Weather RTTY and FAX with the RTL-SDR

YouTube user Tiago Sousa shows how he was able to receive weather Radioteletype (RTTY) data using the RTL-SDR, an upconverter and MultiPSK. Weather RTTY is broadcast by weather services such as the Deutscher Wetterdienst (DWD) which is broadcast from Hamburg, Germany. It is intended for people at sea.

Tiago used an RTL-SDR with upconverter and an 11 meter long wire antenna. For the software he used SDR# and piped the audio to MultiPSK.

Weather RTTY - DWD Hamburg heard in Portugal

Tiago has also uploaded a second video showing him receiving Weatherfax with the same setup. Weatherfax is a signal that transmits a fax image showing weather patterns.

Weather Fax - DWD Hamburg heard in Portugal

Building an Upconverter from the LNA4HF

Adam the manufacturer of the LNA4HF has recently uploaded a video showing how to easily build an upconverter from the LNA4HF. The LNA4HF is a low noise amplifier intended for use with SDRs like the RTL-SDR. The video shows how to connect up two components, the Mixer and Oscillator which are required to create the upconverter.

HF upconverter built from the LNA4HF

Using the RTL-SDR as a Panadapter

PW2VLW’s shows on his blog how to adapt an Icom IC-706 hardware radio to be able to use an RTL-SDR as a cheap panadapter (Note site is in Portuguese, so use Google Translate). A panadapter is device that allows you to visually see the RF spectrum and waterfall being received by the ham radio.

He shows instructions on how to perform the required modification to get the IF output of the ICOM, and also shows how to interface the PC with the ICOM so that it may be controlled directly via HDSDR.

Panadapter
Panadapter

RTL-SDR + Upconverter vs. Portable Shortwave Receiver

Akos from the SDR for Mariners blog has put together an article doing a comparison between the RTL-SDR + ham-it-up upconverter and a Grunding G8 Traveler II Digital conventional portable hardware shortwave radio.

His results show that the RTL-SDR and portable receiver are comparable in terms of performance, with a slight edge to the RTL-SDR. He adds that software tweaks available in SDR# can improve the voice quality for the RTL-SDR. However his final recommendation for general shortwave listening is that the portable is still the better option due to it’s ease of use.

RTL-SDR + Upconverter vs. Portable Shortwave Radio
RTL-SDR + Upconverter vs. Portable Shortwave Radio

KN0CK and KF7LZE Custom HF RTL-SDR Receiver Revision 5

Update: KN0CKs products are now available at http://www.kn0ck.com/HF_SDR/.

Previously on this blog we’ve seen KN0CK release his custom modified RTL-SDR tuners which have built in upconverters for accessing the HF bands. Revision 5 of the KN0CK receiver is now almost ready for sale, and will be sold over at KF7LZE’s webstore Easy-Kits.com.

Revision 5 promises to be lower priced as it will run using the direct sampling mod instead of using an upconverter which would require more components. It will also use a Mini-Circuits MAR 8 wideband amplifier to improve weak signal performance.

Kn0CK and KF7LZE RTL-SDR HF Receiver Rev. 5
Kn0CK and KF7LZE RTL-SDR HF Receiver Rev. 5