Thanks Mike Not had any experience with TV cards as you may be able to tell! I made a 'splitter' ( two monitors from one graphics card ) last night and witnessed the degradation of the signal. However this may well be the way to go. Thanks Graham North -----Original Message----- From: Michael Rigby-Jones [SMTP:mrjones@NORTELNETWORKS.COM] Sent: 25 May 2000 10:58 To: PICLIST@MITVMA.MIT.EDU Subject: Re: [OT]:Video card output in dos? No, the output of VGA cards with TV out is not a (75 Ohm) UHF signal, it's a 50 Ohm composite video signal, at least on all the cards I've seen it is. You will need to have some form of composite video in on the TV's, such as either the old phono style connector or the newer Scart type. The video output from the card has an impedance of 50 Ohms. To correctly terminate this and stop reflections which really upset the picture, you must terminate this with a 50 Ohm load. Now the TV composite in is a 50 Ohm load, so normally you would just plug the video out on your card to the back of the TV and everything would be fine. If, however, you try to connect the same source to two TV's, it will see a load of 25 Ohms (50/2). You will still get some kind of picture, but the chances of "ghosting" occuring are quite high, and on a computer generated signal this means that any text will be pretty well unreadable. You could ouput the compostite signal into a modulator to convert this UHF and then distribute it with an aerial amp, but you will definately lose a lot of quality. The modulators come in small metal cans that accept video in, sometimes sound in, power and have a coax connector for the TV out. Nintendo etc use them to connect their consoles to a TV. The proffesional solution would be a proper distribution amplifier, but I suspect that this item will have a "professional" price tag! Regards Mike > -----Original Message----- > From: Graham North [SMTP:graham.north@LANDINST.COM] > Sent: Thursday, May 25, 2000 10:04 AM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [OT]:Video card output in dos? > > Thanks for the info. > > What exactly do you mean when you say it must be terminated properly? > > I was planning on connecting the output from the card into a cheap TV > mains > amplifer, and connecting the other TV's to this. > > Is this OK? > > Thanks > > Graham North > > -----Original Message----- > From: Michael Rigby-Jones [SMTP:mrjones@NORTELNETWORKS.COM] > Sent: 25 May 2000 09:51 > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [OT]:Video card output in dos? > > > -----Original Message----- > > From: Graham North [SMTP:graham.north@LANDINST.COM] > > Sent: Thursday, May 25, 2000 9:39 AM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: [OT]:Video card output in dos? > > > > Hi all. > > > > You may remember a post by me asking how many monitors could be > powered > > from > > one graphics card. Well I am still playing with multiple > monitors. > > > > Here is my problem. > > > > I race model cars and my local club is holding a regional event > in > a > > couple > > of weeks. The software used runs in dos (it needs total control > of the > > com > > ports). We would like to have monitors around the track for the > refs and > > spectators. > > > > There is a system we could buy but it would cost over £400. > > > > My friend suggested the idea of using a TV card with an analogue > output > > and > > send the picture via coax to portable TV's set up around the > track. > > > > What I am trying to ask is whether there will be an output from > the card > > while the dos software is running? > > > > Sorry for the long post, hope someone can help me on this. If > you > have > > any > > other ideas how I could do this then please let me know. > > > > Thanks > > > > Graham North > > > The answer is a definate maybe. I have an NVIDIA Riva128 card > with > TV out, > and also an ATI Expert@Play (Rage Pro chipset I think). TV out > works OK, > under windows, but when the PC is booting and still in text mode, > my > TV > (addmitedly rather ancient) dosen't seem to be able to handle > whatever > refresh rate the card is giving out, I get a flickering, rolling > picture > (maybe defaulting to NTSC?). I've not tried booting striaght into > DOS which > I imagaine would give the same results, but I can use a DOS box > under > windows. > > The composite output is a 50 Ohm source which must be correctly > terminated. > You can't just feed it to lots of TV's without serious picture > degradation > (and it's bad enough to start with) You will need some kind of > distibution > amp, which should be reasonably simple to make using e.g. high > speed > op-amps > or a discreet transistor design. > > So I guess the answer is that it probably depends if the card you > are going > to use has some kind of dos support such as a utility run from > autoexec.bat/config.sys to setup the TV mode properly. > > Cheers > > Mike