Re: [44net] OFDM Modem

Not cheap, but I'm using a Kuhne amplifier for 70cm. https://www.kuhne-electronic.de/funk/en/shop/industrial/prof-power-amplifie… You can order it with a 40 dB gain option. Also, hams can order industrial equipment from Kuhne no problem. Here it is outputting 2 watts average power. This is DVB-S2 8PSK. The spike on the right is the DC offset of the B210 shifted out of the passband. http://www.w6rz.net/2ws2.png and 4 watts. The PAPR of DVB-S2 8PSK is about 4.6 dB, so the PEP is around 12 watts. http://www.w6rz.net/4ws2.png Ron W6RZ On 09/01/2017 06:36 PM, David Ranch wrote: > > Very interesting project there Ron and thanks for sharing! One thing > that I've been wanting to ask and you might be able to answer is: what > options do people have to give something like this setup some real > POWER? SDRs like an Ettus B200 are amazing but with a power output of > only 10dbm (0.01w), it drastically reduces the real world uses of it. > I know that lots of people say gain is cheap but to do it cleanly for > say a full 8Mhz at say 10w is not exactly simple. I'll completely > leave the legality of the spectrum width here to other folks. ;-) > > --David > KI6ZHD > > > > On 08/31/2017 03:06 PM, Ron Economos wrote: >> Hopefully this isn't too far off topic. I've just completed testing >> of an OFDM modem using IP over DVB-T2. It uses an SDR transmitter and >> a commercial DVB-T2 receiver to implement the RFC 4326 Unidirectional >> Lightweight Encapsulation (ULE) for Transmission of IP Datagrams over >> an MPEG-2 Transport Stream (TS). ULE is supported in the Linux kernel >> for DVB receivers. >> >> https://tools.ietf.org/html/rfc4326 >> >> It's a full-duplex modem capable of up to 50 Mbps (in both >> directions) in an 8 MHz bandwidth. The current test bed consists of >> an Ettus B200 SDR transmitter, PCTV 292e DVB-T2 USB receiver, Kuhne >> down converters for 13cm and 9cm, Microlab BK-26N diplexer and >> RFSpace TSA600 Vivaldi antenna. >> >> http://www.w6rz.net/IMG_0119.jpg >> >> http://www.w6rz.net/traceroute.png >> >> The transmitter is based on the DVB-T2 transmitter in GNU Radio and >> uses this OOT module for the ULE protocol. >> >> https://github.com/drmpeg/gr-ule >> >> To reduce the latency, I've merged the DVB-T2 blocks to avoid having >> so many buffers between blocks. >> >> https://github.com/drmpeg/gr-dvbt2ll >> >> Current test frequencies are 2305 and 3429 MHz with an 8 MHz >> bandwidth. The bit-rate is 28.6 Mbps (symmetrical). >> >> It's intended to replace commercial WiFi equipment for amateur WAN >> interlinks. >> >> Advantages: >> >> 1) Full-duplex. Adding power amplifiers, preamps, diplexers/duplexers >> is easy. >> >> 2) Frequency agile. Can work on any band above 420 MHz. 70cm through >> 5cm direct TX from the SDR and millimeter frequencies with an >> up-converter. >> >> 3) Bandwidth agile. 5, 6 ,7 and 8 MHz bandwidths. >> >> 4) May be legal on 70cm. Although I haven't implemented it yet, a >> small portion of the bandwidth can be used to send a low-rate video >> stream (for example, a still picture of your call sign for ID). This >> would classify the emission as digital ATV, not data. >> >> Disadvantages: >> >> 1) Latency is a bit high. It's currently 100 ms (200 ms round trip). >> This is a function of buffering in GNU Radio and the USB 3.0 >> connection to the SDR. An FPGA implementation of DVB-T2 and a >> different SDR architecture could solve this. >> >> 2) Cost. It's difficult to compete with commercial WiFi equipment. >> However, lower cost components can be used instead of the "Cadillac" >> test bed I constructed. For example, a ADALM-PLUTO at $99 could be >> used instead of the Ettus B200 for transmit. Two antennas instead of >> a diplexer and lower cost down-converters than the Kuhne units. >> >> 3) Requires a Linux computer to run it. An Odroid XU4 may be >> adequate, but I haven't tested it. >> >> 73, >> >> Ron W6RZ >> >> >> _________________________________________ >> 44Net mailing list >> 44Net(a)hamradio.ucsd.edu >> http://hamradio.ucsd.edu/mailman/listinfo/44net > >