On Sun, Feb 28, 2010 at 12:50:07AM +0000, Gordon JC Pearce wrote: So if I understand this well the input (which has to be in the audio range) is a complex signal already near to zero Hz carrier and the plugin shifts it to exactly zero ? Does it do SSB as well ? Ciao, -- FA O tu, che porte, correndo si ? E guerra e morte !

On Saturday 27 February 2010, Folderol wrote: Why were you laughing? Zenith did this, with a self excited circuit, using a type 6BN6 gated beam tube to recover the audio directly from the 4.5 mhz inter carrier frequency, starting in the fall of '51 with the intro of the '52 model year. It worked fairly well too. Stable, not sensitive to the fine tuning setting, so folks out in the fringes could tune for a slightly better if not as sharp a pix. I even made a minor improvement to the circuit that reduced the AM sensitivity noticeably that was incorporated into the next 3 years production runs. I was all of 17 at the time and working in the service dept., the only one, at a zenith wholesaler. It still, like all tv's of the day, had some synch buzz, and it took the FCC 35 damned years to let us broadcasters fix that. As the CE of a tv station, one of the things I did when they allowed us to experimentally reduce the aural transmitters power output from 100% of visual to 20%, was to try 10% on the sly, which helped even more. Then a year or so after I came to WV, I thought 5% might be worth a try, but couldn't get even a bad final tube that low, so I bypassed it one night, saving us many KW a day in electricity since the final took 12 volts at 180 amps (2160 watts/hour just to light it up, and used about 10KW/hour in high voltage draw) which took it down to about 900 watts from the driver stage output, compared to 26kw of visual, figuring I would hook it back up if the phone started ringing. 18 years later the phone still hadn't rung. The tubes were out of production & tired, and it was down to about 500 watts when we turned it off (NTSC) for good. Nary a complaint in all that time about weak signal, not even from the cable folks. Quadrature detection works, and there are even some integrated circuits that do that, they take an fm signal in, need about 6 parts including a tuned coil circuit for the frequency of the fm input, work at less than 1% THD at 4.5 mhz with its +-25khz modulation, or about 1% THD at 10.7 mhz with its wider modulation. If you need any lower THD than that, go find a 50 year old McIntosh C8 tuner and restore it. They were, in their day, the absolute cream of the crop and to my extended knowledge, such performance has never been even close to duplicated at any price, and that one was con$iderable when new in '60. Yeah, I'll plead guilty to being an old fart, 75 now. And its been one hell of a ride to get to this day. Mostly enjoyable, I'd do it again almost exactly as it happened. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) I did this 'cause Linux gives me a woody. It doesn't generate revenue. -- Dave '-ddt->` Taylor, announcing DOOM for Linux

On Sat, 27 Feb 2010 22:50:02 -0500 Gene Heskett &lt;gene.heskett(a)verizon.net&gt; wrote: < snip .. very interesting stuff actually :) > That must have been in the USA I guess, over here the intercarrier is 6MHz Us young 'uns laughed on two levels. The first was that most of us didn't have a clue how the things worked, due to pathetic instruction from our employers (I'm looking at you Radio Rentals). When asked what, exactly, quadrature demodulation was, there was a pregnant pause after which the instructor said 'Well it's demod in quadrature of course' then swiftly moved on to the next topic. Our next cause of merriment was the horrendous EH90 heptode (yes I did say heptode) implementation. See, it scarred as all so badly I can still remember the precise details! The screen feed was via an 18k - 5k6 potential divider, only there was something very strange about the composition resistors used for this. In the first place they were under-rated (especially the 18k. If you did the math you could prove it. Secondly, where resistors normally go high if they overheat these went low, so a nice little thermal runaway ensued. This actually set fire to the (paxolin) PCB, burning a hole through it. If you were very unlucky it also cooked up a wirewound resistor further along the board, which then de-soldered itself, arced and burned another hole in the board. In those days we were expected to fix these things on site, so after scraping out all the carbon, you were left with point-to-point wiring across the gaping holes, supporting the replacement components as best you could. Such fun we had! -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song.

"Solder-head: Rhyme of the repair technician" Version 0.0.0.1 I made my bread for many years, all circuits known to man. From USA and Britain, and from Sweden and Japan. When cheap hi-tech met lust for crap, I could no longer face it. For everything today my friend, is module replacement! I'm thankful for computer skills, they might keep me afloat. I wrote this application, in which I wrote this note.

On Mon, 2010-03-01 at 20:15 -0500, Gene Heskett wrote: Especially these days, when everything is broken by design :-D

On February 27, 2010 07:50:07 pm Gordon JC Pearce wrote: I read about this in Nuts And Volts magazine. They describe in some detail how SDR works and neat DSP techniques in general. I searched the web but could only seem to find Windows related stuff. Some more Linux stuff would be cool. One still needs to build or buy a front-end first though, right? Tim.

On Sat, 2010-02-27 at 22:06 -0500, Tim E. Real wrote: You can buy a Softrock kit for about £10 as an entry-level approach to it. If you feel particularly hardcore you can build your own; there's not a lot to it. Gordon MM0YEQ

Pardon the ignorance, but are the RF signals brought down to AF before AD conversion? Otherwise, it sounds like a silly SR will be needed. Is this the flowchart? antenna -> RF demodulation -> ADC -> your software -> DAC -> audio So what exactly does your plugin do? Victor On 28 Feb 2010, at 10:28, Gordon JC Pearce wrote:

On Sun, Feb 28, 2010 at 11:46:21PM +0000, Gordon JC Pearce wrote: It's similar to Steve Harris' Bode Shifter plugin, except that this takes a single (real) signal and converts it to complex internally using a Hilbert transform. Ciao, -- FA O tu, che porte, correndo si ? E guerra e morte !

On Sunday 28 February 2010, Gordon JC Pearce wrote: So did mine Gordon, heck, while I know what it is, and that its symetrical, I could write an FFT or even a butterfly transform with a gun to my head. But I have sure made heavy use of gear that can do it over the years. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Aren't we lucky our documentation is so sparse noone can accuse us of being inconsistent? 8) - Rusty Russell on linux-kernel

On Sat, Feb 27, 2010 at 10:06:44PM -0500, Tim E. Real wrote: I lost the link, but there are open-source RF interfaces for Linux. IIRC quite powerful stuff as well. Ciao, -- FA O tu, che porte, correndo si ? E guerra e morte !