Allan Herriman wrote:>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 > >I said big FM transmitters. 100kW ERP from a silicon final stage? I haven't seem that used Up to a couple of kW things are OK, but you need to stack too many well matched transistors to keep scaling things. Minor mismatches cause a lot of stress, and reliability tends to be rather poor. Regards, Steve
PM demodulation
Started by ●November 2, 2004
Reply by ●November 4, 20042004-11-04
Reply by ●November 5, 20042004-11-05
Jerry Avins <jya@ieee.org> wrote in message news:<2uv024F2fvkf5U1@uni-berlin.de>...> Randy Yates wrote: > > > 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. > > If you want to think about old technology, consider amplidynes and the > magamps that drove them. Some were used in the servos that rotated > battleship turrets in WW II. The transducers were selsyns. What scares > me is that I know how to build that stuff. Crudely, at least.Don't you worry. I wouldn't consider that scary until you actually built one of the things from wire and carboeard, in order to operate the garden gate in front of your house. ;) Rune
Reply by ●November 5, 20042004-11-05
On Thu, 04 Nov 2004 07:18:19 +0100, Sam <totalsam-n.o-s.p.a.m@hotmail.com> wrote:>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 ! > >SamHi, is the signal you want to demodulate a real-only signal, or is it a complex (quadrature) signal with I & Q samples? [-Rick-]
Reply by ●November 5, 20042004-11-05
r.lyons@_BOGUS_ieee.org (Rick Lyons) writes:> On Thu, 04 Nov 2004 07:18:19 +0100, Sam > <totalsam-n.o-s.p.a.m@hotmail.com> wrote: > > >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 > > Hi, > is the signal you want to demodulate a > real-only signal, or is it a complex > (quadrature) signal with I & Q samples?Hey Rick, Haven't you been listening to Jerry all these years? THERE'S NO SUCH THING AS A COMPLEX SIGNAL!!!! :) --Randy -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA randy.yates@sonyericsson.com, 919-472-1124
Reply by ●November 5, 20042004-11-05
> Hi, > is the signal you want to demodulate a > real-only signal, or is it a complex > (quadrature) signal with I & Q samples? > > [-Rick-] >Hi ! It is a real-only signal... Sam
Reply by ●November 5, 20042004-11-05
Randy Yates wrote:> r.lyons@_BOGUS_ieee.org (Rick Lyons) writes: > > >>On Thu, 04 Nov 2004 07:18:19 +0100, Sam >><totalsam-n.o-s.p.a.m@hotmail.com> wrote: >> >> >>>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 >> >>Hi, >> is the signal you want to demodulate a >>real-only signal, or is it a complex >>(quadrature) signal with I & Q samples? > > > Hey Rick, > > Haven't you been listening to Jerry all these years? > THERE'S NO SUCH THING AS A COMPLEX SIGNAL!!!! > > :) > > --RandyNot on one wire there isn't. On the other hand, if you use quadrature modulation and orthogonally polarized signals, You can transmit 8 KHz worth of signal in 4 KHz of bandwidth. :-) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 5, 20042004-11-05
Jerry Avins <jya@ieee.org> writes:> [...] > On the other hand, if you use quadrature modulation and orthogonally > polarized signals, You can transmit 8 KHz worth of signal in 4 KHz > of bandwidth. :-)I'd say that we always have 8 kHz worth of bandwidth available - we just don't always use it. -- Randy Yates Sony Ericsson Mobile Communications Research Triangle Park, NC, USA randy.yates@sonyericsson.com, 919-472-1124
Reply by ●November 5, 20042004-11-05
Randy Yates wrote:> Jerry Avins <jya@ieee.org> writes: > >>[...] >>On the other hand, if you use quadrature modulation and orthogonally >>polarized signals, You can transmit 8 KHz worth of signal in 4 KHz >>of bandwidth. :-) > > > I'd say that we always have 8 kHz worth of bandwidth available - we > just don't always use it.True, but it's hard to take advantage of orthogonal polarization om a wire. That was my point. jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●November 5, 20042004-11-05
Jerry Avins wrote:> Randy Yates wrote:(snip)>>I'd say that we always have 8 kHz worth of bandwidth available - we >>just don't always use it.> True, but it's hard to take advantage of orthogonal polarization om a > wire. That was my point.Do you count quadrature modulation, as in the NTSC color subcarrier? But since it is double sideband supressed carrier AM, each takes twice the bandwidth already, so pretty much you are just getting that back again. -- glen
Reply by ●November 5, 20042004-11-05
Jerry Avins <jya@ieee.org> writes:> Randy Yates wrote: > >> Jerry Avins <jya@ieee.org> writes: >> >>>[...] >>>On the other hand, if you use quadrature modulation and orthogonally >>>polarized signals, You can transmit 8 KHz worth of signal in 4 KHz >>>of bandwidth. :-) >> >> >> I'd say that we always have 8 kHz worth of bandwidth available - we >> just don't always use it. > > True, but it's hard to take advantage of orthogonal polarization om a > wire. That was my point.You mean like vertical and horizontal? You know, I think I'm still confused on this point after 25 freaking years of engineering! For example, why is it that you can apparently get a complex signal down a wire FOR THE SAME BANDWIDTH as a real signal by using QPSK (looked at as two orthogonal bitstreams encoded on a sin and cos carrier)? -- % Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven. %% Fuquay-Varina, NC % She love the way Puccini lays down a tune, and %%% 919-577-9882 % Verdi's always creepin' from her room." %%%% <yates@ieee.org> % "Rockaria", *A New World Record*, ELO http://home.earthlink.net/~yatescr
