Tagged: ham radio

The Open Source OVI-40 SDR Transceiver

Thanks to various contributors for letting us know about the OVI-40, a new open source DIY SDR ham radio transceiver project that is now available for ordering. The OVI-40 appears to be a German project that is based on the mcHF transceiver. It is a standalone SDR transceiver (no PC required) with a frequency range of DC - 75 MHz. Most discussion appears to be happening in German on their forums, so it is a little difficult to get English information about it.

The kit has recently been released for preorder. The transceiver is a kit involving SMD soldering, but can be ordered fully soldered for 202 Euros (~$240 US) + taxes. The LCD screen is an additional 24 - 27 Euros. The kit without soldering done costs 112 Euros (~$132 US) + taxes.

The advertised details and specs are listed below:

OVI40-SDR is a transceiver which covers VLF...75MHz. It is mainly a DIY project - but all PCBs will also be available as soldered, aligned / programmed PCBs for all those, who do not have the skill to build a complex SMD project by themself or do not want it. OVI40-SDR will also be available as "only RX" and can be expanded with TX stages later.

Developer team takes inspirations from all existing commercial and DIY projects to get a SDR which combines possibly the best of all of them. But OVI40-SDR is not only a TRX - it is a philosophy. A community based working together, regardless of different countries, languages, religions, political systems - all are working together to get a very nice transceiver for themselfes and for others who are coming to the project later - wants to show, what people can reach if they are working together and do not struggle against each other. HAM radio always has connected the world - using the possibilities of the internet adds much more power for community working.

  • RX from VLF (~ a few KHz) ... 4m, possibly 2m Including
  • TX 160m ... 4m: 50W, 2200m, 630m and 4m (2m if Implemented): 10 ... 20mW SMA Out
  • continuosly tuned preselection
  • PA works using double LDMOSFET, independent BIAS adjusted. BIAS is internally Measured via A / D and can be set in menu Directly in [mA].
  • TX and RX mixer with very low capacity to minimize LO leakage
  • true RX QSD mixer using instrumental amplifiers
  • all internal Voltages (8V, 5V) are generated using well-shielded switching regulators. Additionally switching frequency is shifted via firmware so that never harmonics are present in the RX spectrum
  • included hardware for measuring antenna (sweep) using logarithmic amplifier
  • output of an independent selectable rf to SMA plug. I am experimenting to use this as a beacon WSPR Which can run parallel to radio
  • usage as possible network analyzer
The OVI-40 Kit Assembled
The OVI-40 Kit Assembled

SvxLink Now Supports the RTL-SDR

SvxLink is an EchoLink and general purpose voice services system for controlling ham radio repeaters. A repeater is a radio tower that receives a weak transmission from a handheld or remote radio and then repeats the same message with greater power over a wide area. With repeaters radio communications can cover a much further distance.

Ham radio enthusiasts often set up repeaters for their own frequencies, so that they can be heard over a wider range. To control the repeater software like SvxLink is required. In the latest software update of SvxLink they added RTL-SDR support. They write:

The biggest news in this release is the support for RTL2832U based DVB-T USB dongles. This make it possible to use such USB dongles as cheap SDR (Software Defined Radio) receivers. This will open up the world of cheap receiver hardware to all SvxLink users. It will for example be very cheap to set up an extra receiver with local coverage for a SvxLink based repeater, as long as there is a network connection to the repeater. The modulation forms supported are: FM, FM narrow, AM, AM narrow, USB, LSB, CW, CW wide and wideband FM (broadcast). Running multiple receivers on the same dongle is supported as well as using multiple dongles.

SvxLink Logo

 

Receiving BPSK63 with an RTL-SDR and Ham-It-Up Upconverter

Over on YouTube user Java’s Toys has uploaded a video showing a demo of his reception of a BPSK63 signal using his RTL-SDR and the Ham-it-up upconverter. BPSK63 is a text based digital communications mode used by ham radio enthusiasts to make contacts. It is twice as fast compared to the more commonly used BPSK31 mode.

Java’s toys used HDSDR together with Fldigi to receive and decode the signal.

Decoding D-STAR Headers with the RTL-SDR

D-STAR or Digital Smart Technologies for Amateur Radio is a digital voice and data protocol used in amateur radio. I was tweeted a link earlier which shows how the RTL-SDR can decode D-STAR text messages and headers (link is in Italian but Google translate can help, and the pictures show more than enough information). By using SDRSharp and stereo mix you can tune to a D-STAR signal, and pass the audio to a command line based decoding program (dstar.exe) which can be downloaded from the above link, which will then decode D-STAR text messages.

dstar7

Here is also an older video showing D-STAR decoding with HDSDR in action.

RTL-SDR as a Cheap Panadapter

For people already with expensive ham radios, the RTL-SDR can be used as a cheap panadapter. A panadapter is device that allows you to visually see the RF spectrum and waterfall being received by the ham radio. There are multiple (expensive) commercial panadapters available, but combined with a PC or laptop, the RTL-SDR will work just as well.

In this video YouTube user akdude47 shows a tutorial on setting up the RTL-SDR as a panadapter for a Yaesu FT-857. The setup involves connecting the IF output of the radio to the RTL-SDR, and putting in some settings into HDSDR.

Receiving SSTV with RTL-SDR

Over on the Radio Antics blog fellow RTL-SDR enthusiast Andrew has been using the RTL-SDR to receive Slow Scan Television (SSTV) amateur signals. SSTV is a method ham radio enthusiasts use to send small images to one another. The images often contain their ham call sign overlaid on the image.

Andrew was able to receive several SSTV images using an R820T dongle tuned to the 27 MHz (11 meter) band. He also used a Funcube Dongle+ and got similar results.

Check out his post for some of the images he received, and his video below for an example of the receiving process.

RTL-SDR Tutorial: Decoding DRM Radio

Digital Radio Monodial (DRM) radio is a type of digital shortwave radio signal that is used by international shortwave radio broadcasters. It provides superior audio quality compared to AM signals by using digital audio encoding. With an upconverter, good antenna, and decoding software the RTL-SDR software defined radio can receive and decode DRM signals. This tutorial is also applicable to other software defined radios that can receive HF with or without an upconverter, such as the HackRF, Airspy, Softrock and Funcube dongle.

Examples of DRM Decoding

YouTube user Superphish shows DRM reception with his Ham-it-up upconverter, and rtl-sdr.

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