[WaveRider] is using a type of phase shift keying called BPSK to transmit digital sound and video for remote telemetry. Though a higher signal to noise ratio (SNR) is generally sought after with communications, legal limitations are imposed on total radiated power. To balance the two headed beast, he opted out on frequency shift keying due to binary shift keying’s ability to work with lower SNR. This adds the difficulty of properly reconstructing the digital signal at the receiver. A PLL based carrier regeneration circuit is used to reconstruct the signal. Using the Rabit2000 processor as the host controller on both transmitter and receiver, 96KB/Sec serial data is obtained. On the other side of the spectrum is the Homemade regenerative tube radio.
Ok. I don’t get this hack at all. Besides there is no arduino :P
burp
excellent hack
I was hoping for a nice open source 8-bit software-based modulation/demodulation implementation.
concino: think of the rabbit2000 module as an arduino. But trust me when I say to avoid them like the plague.
^ watership down !!!
great hack btw – i’ve never done any hifreq rf projects, but i have respect for those who can fab that kind of stuff.
Nice build.
If he had utilised some form of forward error correction scheme you can obtain the same BER as BPSK with 4-QAM, which would increase the spectral efficiency and in turn increase the throughput.
Software Defined Radio (SDR) would be a nice platform to initially build and mess around with structures without building an application specific circuit, it would allow interleaving, FEC, puncturing, etc to be implemented easier.
I wonder why he chose BPSK instead of something like QAM. QAM would’ve given him higher bitrates.
@qam: Probably because BPSK and QPSK are essentially 2-QAM and 4-QAM.
4QAM is not QPSK, they are similar in nature, but also slightly different. Many authors simply class them as one scheme which is wrong.
4QAM produces a slightly better result over an AWGN channel, but QPSK is more suitable for producing a resilient OFDM mapped signal.
utilising FEC, interleaving, etc will result in them producing almost identical BER vs SNR waterfall graphs. which you see in almost any referenced material.
A large number of satiellites use BPSK along with SDR to transmit images, etc. The work would be good for receiving data along those lines.