Over on YouTube user radio innovation has uploaded a brief screen capture showing his Raspberry Pi 3 and RTL-SDR dongle being used as an always-on monitor for low transmit power based signals such as FT8, JT65 and JT9. These signals are transmitted by ham radio enthusiasts for the purpose of making contacts, and determining propagation conditions. This is a good application for an RTL-SDR and Raspberry Pi 3 as it enables cheap monitoring of these signals without the need to tie up a full sized ham radio.
To do this "radio innovation" runs Linrad on the Raspberry Pi, which is a program like GQRX that interfaces with the RTL-SDR dongle. Then the WSJTx software is used to decode the signals. He writes:
Remote Desktop screencapture of my Raspberry Pi3 monitor receiver on 40m amateurradio band with WSJTx and decoding FT8,JT65 and JT9. Receiver hardware is RTL-SDR(tcxo) + simple converter and homemade bandpass filter.
Over on YouTube FairlawnARC.org have uploaded a talk about SDRs and ham radio by Ria Jairam (N2RJ0). The talk is a good overview of the current state of SDRs for ham radio use, and she discusses the various hardware and software options as well as giving many tips for improving your ham station. The blurb reads:
Our speaker was Ria Jairam (N2RJ), a world class contest operator and member of the Frankford Radio Club. Ria discussed the latest technology and offerings from Flex Radio, the HPSDR project (Ananradios), RTL SDR and others, as well as practical tips for contesting, DXing and rag chewing using your SDR. This presentation was held on Friday, October 20, 2017, 1900 hours at the Fair Lawn Senior Center, 11-05 Gardiner Road, Fair Lawn, NJ. The event was open to the public & refreshments were served.
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
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.
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.
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.
Here is also an older video showing D-STAR decoding with HDSDR in action.
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.