9666	2014-01-20 03:56:36	Ashhar Farhan	ssb out of the raspberry pi
Message	Date	From	Subject
is this for real? http://pe1nnz.nl.eu.org/2013/05/direct-ssb-generation-on-pll.html basically, it claims that you read the mic, figure out the frequency and amplitude of the signal and move the PLL and change the amplitude. i can imagine doing this for a single tone. how does it simulate multi-tone modulation? what about the none sinusoidal stuff like the sound of 'rrrr' and 'kkkk'? i spent some years porting voice codecs so my gut feel is that this can't be it. but then, i may be wrong. - f
9667	2014-01-20 13:24:48	Corey Minyard	Re: ssb out of the raspberry pi

9668	2014-01-20 15:56:35	kb1gmx	Re: ssb out of the raspberry pi
>>>I've actually been pondering if this could be done. The ARRL homebrew contest had a winner (David Cripe) that built an amplifier that extracted the amplitude and frequency separately and used a class E amplifier to amplify the frequency portion and a audio power transistor to control the amplitude of the amplifier. If that's possible, it should be possible to directly synthesize the amplitude and frequency.<<< While his approach was by far the most interesting I'd seen. There is a huge gap between detecting amplitude and using that to modulate a saturated [switch mode] amp and creating SSB on the fly. One is easily done with simple analog circuits while the other is a true tour de force of mathematics at high speed. I've looked at the possibility of using the Raspberry Pi to run the usual baseband transceiver software to use with something like the Softrock RXTX ensamble. Its get enough processing power for that and then some. So I'd expect some of the more aggressive methods are will within the range of the 'Pi. The little RaspberryPi is a lot of processing power in a small package and price. Allison/Kb1GMX
9669	2014-01-20 15:56:47	Eamon Egan	Re: ssb out of the raspberry pi
I never heard that SSB was reducible to an FM modulation. Here is one of the comments. I think there is such a silence because this technique does not work.. sorry. Had a go at coding it myself, then realized you cannot get fundamentally AM sidebands by just FMing a constant carrier, no matter how cleverly.. anyone else had a go? Hugh G6AIG - Eamon VE2EGN
9670	2014-01-20 17:16:59	Ashhar Farhan	Re: ssb out of the raspberry pi
There was a very brief mention of this simultaneous envelop and frequency modulation of carrier to generate SSB in the EMRFD. The citation is unfortunately behind a paywall. - f
9671	2014-01-20 18:00:22	iq_rx	Re: ssb out of the raspberry pi
The technique of generating an SSB signal, either electrical or mathematical, separating it into envelope and phase modulated components, amplifying the phase modulated component with a saturated (perhaps class C) amplifier and then putting the envelope back on with a high level modulator has been widely known since the early 1950s. The best known amateur radio example is the 8 watt linear mode B transponder in Oscar 7, launched in 1974, designed and built by Karl Meinzer DJ4ZC. I have built a number of experimental models on the bench, and friends have built large commercial versions. The technique simulates beautifully using Matlab. As Allison mentioned, the block diagram is compelling and simple, but implementation is difficult--requiring fluency with the both afore mentioned analog signal processing mathematics and the subtleties of envelope modulation--both rare these days, among my graduate students at least. A philosophical difficulty is that the bandwidth of both the envelope and phase modulation must be considerably wider than the actual signal you would like to amplify. The resulting broadband spectral products magically disappear in the mathematics and simulations, but are not as easily suppressed in practice--particularly when efficiency is required. As with phasing SSB generation (and for similar reasons) it is relatively easy to generate a two-tone SSB output signal that has all the undesired outputs 20 dB down from either of the two tones. 30 dB down requires more care, and 40 dB indicates a carefully engineered, highly evolved system. Some of the accuracy needed for 40 dB suppression of wideband distortion products requires burning current, and one might be better off with a conventional linear amplifier. That has often been the conclusion for nearly 6 decades. Some modern modulation techniques are more suitable than SSB for separating the envelope and phase and recombining them at the final or penultimate stage. The technique has been given many names, the oldest and arguably most respected is the Envelope Elimination and Restoration or EER technique. More recently, Polar Modulation has been applied. To read more, Google EER, Frederick Raab, Leonard Kahn, and follow the links. Phase modulation is relatively easy, but it is quite amusing to design and build high quality envelope modulation systems, and a challenge to get beautiful pictures on the scope. I suspect that some of the modern AM crowd is having an awful lot of fun, and students who understand envelope modulation are in high demand in some wireless circles. Incidently, the recent QST article that compares the effectiveness of various modes in dB contradicts 6 decades of very careful amateur and professional communications theory and measurements, much of which was reported in QST in an earlier era. I wonder how it got past the reviewers. Best Regards, Rick KK7B
9673	2014-01-21 03:00:41	Stephen Farthing	Re: ssb out of the raspberry pi
Hi guys, Yes, it is for real. I have received Guido's RPi SSB signals on 40 meters transmitted from his shack in the Netherlands here in the UK on my K2. Also my good friends Jan, G0BBL and Alan M0PUB have carried out many experiments with SSB on the Pi using Guido's code. The Pi is an interesting platform for radio work. The big problem is the lack of documentation for the processor. As I recall this is a policy decision by Broadcomm to protect their secret smoke. I have copied Guido in on this. Hopefully he will join the group and share his wisdom with us. Regards, Steve G0XAR
9674	2014-01-21 10:08:11	Russ Ramirez	Re: ssb out of the raspberry pi
I enjoyed your reply Rick, in particular the opening paragraph, and the fourth (which I guess speaks volumes about your application knowledge). re: QST, I think ARRL has lost some technical edge anyway IMO. Russ K0WFS
9675	2014-01-21 10:40:21	johnsorj666	Re: ssb out of the raspberry pi
Hi All If you have interest in using Phase Modulation, you may want to look up the background information on the RCA Ampliphase system used by AM broadcasters. My local AM station, KSTP 1500, used such a transmitter at the 50kW level---please note that this was 40 years ago when I toured their transmitter site so I am not sure if it is still widely used.... Interesting concept though.... ray johnson WB0EBG / KE3QY EN35la
9677	2014-01-22 08:59:03	Don Hackler	Re: ssb out of the raspberry pi
The RCA Ampliphase system hasn't been used by AM broadcasters for quite a while. It was basically a Doherty amplifier system, modified slightly to get around Western Electric patents. It was an interesting concept, but difficult to keep adjusted properly in routine operation. RCA also used special tubes that have not been manufactured for a long time. Most 50Kw stations are digitally modulated solid state rigs now, as they are less expensive to operate. The savings on the power bill paid for the newer technologies quickly. On Jan 21, 2014 10:40 AM, <johnsorj@aol.com> wrote: Hi All If you have interest in using Phase Modulation, you may want to look up the background information on the RCA Ampliphase system used by AM broadcasters. My local AM station, KSTP 1500, used such a transmitter at the 50kW level---please note that this was 40 years ago when I toured their transmitter site so I am not sure if it is still widely used.... Interesting concept though.... ray johnson WB0EBG / KE3QY EN35la
9688	2014-02-02 09:28:45	drmail377	Re: ssb out of the raspberry pi
This may be a bit OT, but the RTL_FM demod lib has just been updated (as of my post time) faster-better is claimed. Can do AM, FM, USB, DSB with a low footprint and resources. This may be a nice candidate for the RPi. Haven't tried a cross compile as of post time, but there should be a binary out there soon. With a bit of work RTL-FM may be adopted for Tx as well as Rx with the proper hardware, I remember seeing it done somewhere (sorry no links folks). RTL_FM UPdated http://www.rtl-sdr.com/rtl_fm-updated/ http://kmkeen.com/rtl-demod-guide/