glen herrmannsfeldt wrote:> > > Randy Yates wrote: > >> Jerry Avins <jya@ieee.org> writes: > > > (snip) > >>> One time, when I worked late on the W2HJ transmitter, I found myself >>> locked into the City College without change for a pay phone. I had >>> finished with the 304 TH final, but the modulator wasn't yet installed. >>> My Morse was poor and I couldn't even find a key in the shack. I didn't >>> want to mess with the VFO, so I soldered two tin-can ends to adjacent >>> turns of the driver tank coil and shouted into the nearer one. With a >>> kilowatt to get across Manhattan, even a little phase modulation is >>> enough. A friendly ham called the cops and they came and let me out. > > >> Quite the story, Jerry!!! But what's the "304 TH final"? > > > Knowing only a tiny bit about how they used to build radio > transmitters, and even less about how they build them now... > > There should be a carrier source, modulator, and final amplifier > (and probably other important details along the way). > > If you don't have a modulator, all you could get is unmodulated > carrier. Now, what is the result of modulating the L or C > of the carrier oscillator?Modulating the oscillator produces FM ideally, and both AM and FM in practice. (Modulated oscillators in transmitters of more than a few milliwatts is not allowed.) Modulating the L or C of subsequent a stage produces PM.> I remember stories about vacuum tube amplifiers (maybe phone preamps) > being vibration sensitive enough that you could get feedback placing > them too near the speakers. Presumably motion of the tube electrodes > changes the electrical properties enough to generate a signal.Yes. Sometimes they were shock mounted. Audio tubes were sometimes rated according to how microphonic they were.> All the fun that went away with transistorized amplifiers.I had one that only worked in the dark.> I presume a 304 TH is a final amplifier.Yes. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
PM demodulation
Started by ●November 2, 2004
Reply by ●November 3, 20042004-11-03
Reply by ●November 3, 20042004-11-03
On Wed, 03 Nov 2004 21:28:54 +0100, Sam <totalsam-n.o-s.p.a.m@hotmail.com> wrote:>Thank you all for these answers ! > >Well, OK, I'll try to find an arctan algorithm (if anyone could show me >one... thanks in advance !) > >But I have another question : do I need to derivate the I and Q >components from two mixer products (one sin and one cos) or is that >possible to simply delay the signal from a few samples to get the Q ?? > >Thanks in advance ! > >SamHi, there are several different ways to I & Q components from a real-only time domain sequence, but you haven't told use anything about your implementation. Is your implementation of this phase demod a MATLAB simulation, using a programmable DSP chip , an ASIC implementation, or what? What is the exact nature of the signal of which you're trying to demod? [-Rick-]
Reply by ●November 3, 20042004-11-03
Tim Wescott <tim@wescottnospamdesign.com> writes:> [...] > 304 TH is a high-power vacuum tube; a "final" is a rig's final amplifier.Anyone who knows tubes has my respect! -- % Randy Yates % "Watching all the days go by... %% Fuquay-Varina, NC % Who are you and who am I?" %%% 919-577-9882 % 'Mission (A World Record)', %%%% <yates@ieee.org> % *A New World Record*, ELO http://home.earthlink.net/~yatescr
Reply by ●November 3, 20042004-11-03
Jerry Avins <jya@ieee.org> writes:> That was in 1952. I might have forgotten some details and > misremembered others.After only 52 years? You da' man, Jerry. Listening to you describe the old tube technology is FASCINATING! -- % Randy Yates % "...the answer lies within your soul %% Fuquay-Varina, NC % 'cause no one knows which side %%% 919-577-9882 % the coin will fall." %%%% <yates@ieee.org> % 'Big Wheels', *Out of the Blue*, ELO http://home.earthlink.net/~yatescr
Reply by ●November 3, 20042004-11-03
Randy Yates wrote:> Jerry Avins <jya@ieee.org> writes: > > >>That was in 1952. I might have forgotten some details and >>misremembered others. > > > After only 52 years? > > You da' man, Jerry. Listening to you describe the old tube technology > is FASCINATING!Tubes aren't that old. There's a great big tube in my TV, a smaller one in my microwave, and plenty of them in orbit. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 4, 20042004-11-04
Jerry Avins wrote:>Randy Yates wrote: > > > >>Jerry Avins <jya@ieee.org> writes: >> >> >> >> >>>That was in 1952. I might have forgotten some details and >>>misremembered others. >>> >>> >>After only 52 years? >> >>You da' man, Jerry. Listening to you describe the old tube technology >>is FASCINATING! >> >> > >Tubes aren't that old. There's a great big tube in my TV, a smaller one >in my microwave, and plenty of them in orbit. > >Jerry > >What's this about old tube technology? What do big FM transmitters use today? Only the exciter has changed since the time Jerry was talking about. Regards, Steve
Reply by ●November 4, 20042004-11-04
Hi Rick, I would like to demodulate signals to make a small analyzer with a FPGA. I will then display on a screen the demodulated time-domain signal. But I try to simulate it with matlab first.... Thanks in advance ! Sam
Reply by ●November 4, 20042004-11-04
Steve Underwood <steveu@dis.org> writes:> [...] > What's this about old tube technology? What do big FM transmitters use > today? Only the exciter has changed since the time Jerry was talking > about.Do you doubt that a freshly-graduated BSEE of the day would most likely know little-to-nothing about tubes? When I was going to DeVry in 1976, I was in the last class that was formally taught tubes - the next class was all transistor. -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA randy.yates@sonyericsson.com, 919-472-1124
Reply by ●November 4, 20042004-11-04
On Thu, 04 Nov 2004 12:25:49 +0800, Steve Underwood <steveu@dis.org> wrote:>Jerry Avins wrote:[snip]>>Tubes aren't that old. There's a great big tube in my TV, a smaller one >>in my microwave, and plenty of them in orbit. >> >>Jerry >> >> >What's this about old tube technology? What do big FM transmitters use >today? Only the exciter has changed since the time Jerry was talking about.All "solid state" finals for broadcast FM have been around since the '80s. At the time, they were better in terms of reliability, but not initial purchase price. I don't know how the comparison stands today. Regards, Allan
Reply by ●November 4, 20042004-11-04
Randy Yates wrote: (snip)> You da' man, Jerry. Listening to you describe the old> tube technology is FASCINATING! Somehow this reminds me of the stories I used to read in Popular Electronics many years ago. Well, our library had back issues that you had to request at the checkout desk, as they were too many to put out on the shelves. There was a series of stories about Carl and Jerry, many of them involving tubes and radio transmitters. Somehow putting Jerry and tubes in the same thought reminded me of them. The library didn't have a complete collection, so I didn't get to read them all. -- glen
