How many people do SDR for HAM purposes? - Page 1
Forum section: electronics / rf-microwave

author: technix
author_rank: Super Contributor
timestamp: May 06, 2020, 07:09:44 pm
content: As asked, how many people do that? In the case when both RX and TX uses SDR, it should be possible for such a station to use literally whatever modulation and protocol theoretically possible as long as it can fit in the bandwidth and compute power afforded to the processors that is running the software.For example, an RTL-SDR plus a LNA + wide-band frequency shift frontend for RX, a USB 3.0 high speed DAC that spits out IF directly plus a frequency shift + PA frontend for TX, all hooked to one PC to do all the actual modulation and demodulation on its CPU cores and GPUs.

author: M0HZH
author_rank: Regular Contributor
timestamp: May 06, 2020, 07:32:49 pm
content: I use a Red Pitaya 125-14 board for HF & 6m, with all the required additional circuitry - filters, amplifiers, switching etc. Previously, Tayloe mixers with a quality local oscillator and a decent computer sound card achieved more or less the same thing.The RTL-SDR is suitable for experiments not for actual practical use, due to the very modest receiver dynamic range. Even entry-level equipment from 50 years ago is better in that aspect. However, if used for sampling IF out of a AGC-controlled heterodyne receiver, it can offer SDR-like signal processing.

author: Bud
author_rank: Super Contributor
timestamp: May 06, 2020, 07:55:08 pm
content: Quote from: technix on May 06, 2020, 07:09:44 pmNo, for transmission you can only use the modulation types that are permitted by the Ham license.

author: technix
author_rank: Super Contributor
timestamp: May 06, 2020, 08:08:33 pm
content: Quote from: M0HZH on May 06, 2020, 07:32:49 pmIn the case if I want to build my own, is 10MHz a good IF? In that case, is 8-bit 25MSPS a good spec for the ADC and the DAC at 10MHz IF? (For use with cheap chips like TLC5602 30MSPS DAC and ADC08351 42MSPS ADC.) What is a good interface solution if I want to rely on the main PC to do all the decoding? (Two streams at 25MSPS 8-bit means 50MB/s, which is close to USB 2.0's theoretical maximum of 60MB/s.)Quote from: Bud on May 06, 2020, 07:55:08 pmAt least here in China, while some bands have modulation restrictions, some other bands allow arbitrary modulation as long as you stay within the band limit. Also there is always subcarriers which can sneak within other types of transmissions, for example a 15kHz subcarrier within an audio transmission operating a QPSK-4 data link.There are stories of Chinese operators, probably using modified telecom equipment, jumping from a 400MHz band SSB voice link straight into a QAM-256 data link with 20MHz bandwidth and hosted a digital video call.

author: 9aplus
author_rank: Regular Contributor
timestamp: May 06, 2020, 08:18:26 pm
content: +1rtl-sdr v2 x1sdrPlay RSP1 x2LimeSDR usb x2LimeNET micro x1dedicated AIS SDR RX x1dedicated ADSB SDR x1All of them, not for HAM only

author: M0HZH
author_rank: Regular Contributor
timestamp: May 07, 2020, 12:48:41 am
content: Quote from: technix on May 06, 2020, 08:08:33 pmHigh performance equipment uses 16-bit ADCs, 14-bit is considered good/above average, 12-bit is entry level stuff and anything below that are just toys. 8-bit is what the RTL-SDR sticks / HackRF etc have.AD9866 might be an interesting part to get started with, has 12-bit ADC & DAC and some other goodies.What frequencies are you aiming for ? Requirements and options are very different from HF to VHF/UHF.

author: radiolistener
author_rank: Super Contributor
timestamp: May 07, 2020, 01:15:20 am
content: Quote from: technix on May 06, 2020, 07:09:44 pma lot of people doing it. You can usePowerSDRsoftware for RX/TX and different hardware, for example seeHermesand other HPSDR projectsYou can start from very nice SDR receiver "SDR-Micron" with very good performance, it has much much better performance than any RTLSDR, SDRplay or AIRSPY:http://www.sdr-deluxe.com/publ/sdr_micron_priemnik_s_prjamoj_ocifrovkoj_i_usb_podkljucheniem/1-1-0-74You can find PCB layout and firmware here:https://github.com/Dfinitski/SDR-Micron

author: dropkick
author_rank: Contributor
timestamp: May 07, 2020, 01:26:42 am
content: +1 on the RTL-SDR sticks. Use them often for quick checks on things VHF and above. Not real high performance but does the job and dirt cheap. Can decode almost all digital ham voice formats with DSD+. Will get an SDRplay if I need something a little better. Also use filtered RTL's for ADS-B 1090 & 978.

author: radiogeek381
author_rank: Regular Contributor
timestamp: May 07, 2020, 01:45:47 pm
content: I've been using an Ettus USRP N200 for more than six years now. First with a WBX (70MHz to 6GHz) more recently with a UBX (10MHz to 6GHz).Original use was as an IF for a 10GHz transceiver. Lately (past couple of years) it has been used for WSPR on 30m and 20m.Software is SoDaRadio: written for the Ettus USRP series.

author: srce
author_rank: Regular Contributor
timestamp: May 07, 2020, 04:16:58 pm
content: Quote from: technix on May 06, 2020, 08:08:33 pmYep - free to experiment in the UK too.

author: jujun
author_rank: Regular Contributor
timestamp: May 08, 2020, 03:25:37 pm
content: A great TX and RX SDR for HF is Hermes Lite V2. Fully open source, including FPGA gateware. Built in 5W power amplifier for TX. Gigabit ethernet to computer. Open source protocol with a lot of compatibles softwares. More info here :https://github.com/softerhardware/Hermes-Lite2