|
Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions. |
|
Thread Tools |
21st Jul 2011, 2:31 pm | #21 | |
Retired Dormant Member
Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,700
|
Re: 405-line o/p from Linux
Quote:
As has been mentioned elsewhere, the syncs produced with simple circuits like these are rather crude and can produce poor interlacing on some sets/monitors. I get slight line-pairing on my Pye professional monitor. I'm intending to design something which produces composite video that's a bit closer to spec. (Feel free to start a "405-line o/p from Windows" thread if you like; it's not an OS which has any relevance to me - or this thread.) Kat |
|
21st Jul 2011, 4:39 pm | #22 |
Retired Dormant Member
Join Date: Jun 2010
Location: Co. Limerick, Ireland.
Posts: 1,183
|
Re: 405-line o/p from Linux
I was only mentioning in passing
(crawls back to bed) |
21st Jul 2011, 4:44 pm | #23 | |
Retired Dormant Member
Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,700
|
Re: 405-line o/p from Linux
Quote:
I did post this circuit (drawn in ASCII) and Darius explained what bits to add to combine all three colours. If I can find the thing or find my notes I'll post another circuit (maybe even drawn properly!) But that and a modulator are all that's needed to connect the VGA output to a 405-line TV (with the possibility of line pairing on some sets.) So there's little incentive to get the 'TV out' on some cards/computers working. (Jeffrey Borinsky put me off the idea in 2006; though I did look into it a little further anyway.) Kat |
|
27th Jan 2013, 7:43 am | #24 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: 405-line o/p from Linux
I am buying a GeForce FX 5200 so I can use MythTV to output to my 405 line tv, now all I have to do is build a VGA to composite adapter and an rf modulator, and install linux and MythTV on a spare computer!
all the realy cheap GeForce FX 5200 graphics cards are agp and I cant find a motherboard with agp. |
27th Jan 2013, 12:42 pm | #25 |
Retired Dormant Member
Join Date: May 2011
Location: Sutton Coldfield, West Midlands, Uk.
Posts: 78
|
Re: 405-line o/p from Linux
audion...
405 line Modulator Design: I have come across this design: www.earlytelevision.org/405_modulator.html. based around a MC1374 chip. It looks a lot easier to put together than the MC1396 design - particularly on Veroboard. I have ordered a couple of ICs and will let you know how I get on. John |
27th Jan 2013, 8:35 pm | #26 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: 405-line o/p from Linux
I have some P1 or 2 motherboards, I will set one up with MythTV to test my Bush tv43.
the 405 line Modulator looks good the kit comes with pcb ICs and ceramic coil forms and for $30 with shipping! |
27th Jan 2013, 8:50 pm | #27 | |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: 405-line o/p from Linux
Quote:
I would realy like to know how you get on with the Modulator, did you order the kit? getting the coil forms and pcb take the guesswork out of it, and I have not build that much RF stuff |
|
28th Jan 2013, 12:16 pm | #28 |
Retired Dormant Member
Join Date: May 2011
Location: Sutton Coldfield, West Midlands, Uk.
Posts: 78
|
Re: 405-line o/p from Linux
If you get the kit, I would be pleased to know how you get on.
Crystals are a problem; 15Mhz ones can be used in third ovrtone mode to give 45MHz, but I elected to use Colpitts oscillators which are stable enough for this application. I have just ordered the bare chips which are on their way. I know it is difficult to find coil formers but a few are available from amateur radio suppliers (few and far between these days) and I have some in my spares box. John |
28th Jan 2013, 4:18 pm | #29 |
Pentode
Join Date: Jan 2012
Location: Worcester, Worcs. UK.
Posts: 112
|
Re: 405-line o/p from Linux
I built one of the ETF modulators, and they work very well. I have mine tuned up on channel B4. You need to experiment a bit with the coils and turn spacing to get the range you need, but once done it seems quite stable, even if not crystal controlled. Steve ships them out quite quickly. You only have to add the rest of the components yourself.
I use it coupled up to my FOTH box, which uses a simple VGA/Sync combiner fed from a Pentium P4 computer and Nvidia GEForce 5200FX adapter. The operating system I use is MythBuntu, but any Linux distro could be used with MythTV added separately. Dont forget, you only really need MythTV if you intend to use a tuner/video input device, or remote media server. You can still play DVDs etc, using the built in Linux media player. If you need a 405/625 code portion to put into the X configuration file, and a simple combiner circuit, let me know - might save some time. It won't approach an Aurora in terms of peformance, but as a signal source for your old tellies, it's fine (for me at least!)
__________________
John |
28th Jan 2013, 5:00 pm | #30 |
Pentode
Join Date: Jan 2012
Location: Worcester, Worcs. UK.
Posts: 112
|
Re: 405-line o/p from Linux
Further to the above, here's a few pics to show how I do it.
The first image shows the Linux box at the bottom, and the video combiner/modulator unit on top of the scope. There is a freeview unit on top of that and a Maplin UHF modulator. Second Picture shows Testcard C off a CD as received from that setup by my EKCO T283. Third picture shows an off air image from the freeview box piped through the video input of the PC's capture card. The Moire patterning that can be seen is a camera artefact, and not on the sceen.
__________________
John |
3rd Feb 2013, 3:33 pm | #31 |
Retired Dormant Member
Join Date: May 2011
Location: Sutton Coldfield, West Midlands, Uk.
Posts: 78
|
Re: 405-line o/p from Linux
405 line modulator
I have built the modulator referred to above video section only and it is working well. The coil is a 5 1/2 turn "Toko" type green with ferrite core. Once I had the circuit wired correctly, it worked first time bang on 45 MHz. I had the coponents handy but it would be easier to order the kit. I fed the modulator from the video output from my Aurora but I am now looking for a simple pattern generator circuit to produce a test sgnal perhaps on another channel. The set is a 17" Ekco T284 -refurbed but not by me- and only roughly set up. The bars are because I used the camera on automatic settimg. |
11th Feb 2013, 8:17 am | #32 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: 405-line o/p from Linux
Can other nVidia graphics cars (cards) with the same GPU as the nVidia GeForce 4 or GeForce FX 5200 card be used for 405 line out?
|
11th Feb 2013, 11:43 am | #33 |
Pentode
Join Date: Jan 2012
Location: Worcester, Worcs. UK.
Posts: 112
|
Re: 405-line o/p from Linux
I don't think anyone has had any other type of graphics card than the nVidia family running like this, but that doesn't necessarily mean they won't work - it's just that the research probably hasn't been done!
I was going to try a few other common graphics cards to see if they could be coerced into being programmed to do 405, but to date haven't had the time to look into it. It's a case of finding one with a suitably programmable dot clock frequency. I don't know if Kat Manton has done any more research into it recently either. Meanwhile, an older P4 with an AGP slot is your best bet to use with the nVidia card
__________________
John |
20th Feb 2013, 12:17 am | #34 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
|
Re: 405-line o/p from Linux
I have payed the $30 for the modulator kit, it will probably take a few weeks to arrive, and I now have two GeForce FX 5200 graphics cards.
|
27th Mar 2013, 8:36 pm | #35 | |
Pentode
Join Date: Oct 2012
Location: Dorset, UK.
Posts: 240
|
Re: 405-line o/p from Linux
Quote:
|
|
28th Mar 2013, 10:28 pm | #36 |
Pentode
Join Date: Jan 2012
Location: Worcester, Worcs. UK.
Posts: 112
|
Re: 405-line o/p from Linux
Hi,
To answer the question, I use MythBuntu 11.10, but I suspect your version will work ok. The graphics card should work if its a GeForce 4 family GPU. Without knowing what you've put into the xorg.conf file, it's difficult to suggest a solution but here's how I approach the overall setup. 1) Use the proprietary nvidia drivers, not the open source ones, which won't work. I think you've got the right one anyway. 2) Build the simple VGA and sync combiner using a single transistor, 3 resistors and a capacitor. You can worry about building something more complex later. In practice, I find it works just fine. I can supply the circuit diagram, or you may find it elsewhere on this forum in earlier threads by Kat Manton, who came up with this idea originally. 3) Connect the above to an oscilloscope. This is by far the best way of confirming your video timings are correct. 4) Do your experiments by using an ssh command line session from a pc to the Linux box over a network connection. If you try to switch the X server to 405 lines while the VGA connection is still attached to a hi-res monitor, it'll flash for a split second, and switch back to the original resolution. This is because the graphics card is detecting the monitor you have connected. Use something like "Teraterm" on another PC, while your Linux box is connected to the scope via the combiner. Alternatively, make your xorg changes and at the point of restarting the X server, disconnect the display and connect your combiner/scope. You should see the composite output on the scope. If the switch to 405 lines works, the sync to sync time should be around 98uS. If it is, you're home and dry. I can make the contents of my xorg.conf available for you to try, if you like. I have both 405 and 625 variations built into mine. There may be a reference issue in yours, which is maybe why it doesn't seem to work.
__________________
John |
29th Mar 2013, 2:50 pm | #37 | |
Pentode
Join Date: Oct 2012
Location: Dorset, UK.
Posts: 240
|
Re: 405-line o/p from Linux
Quote:
|
|
29th Mar 2013, 10:53 pm | #38 |
Pentode
Join Date: Jan 2012
Location: Worcester, Worcs. UK.
Posts: 112
|
Re: 405-line o/p from Linux
That's good news indeed. I too have a Sony 9-90 which is how I first proved it was working. At the time, I didn't have a VHF modulator, so I used a UHF modulator, and did the old two button trick to make it do 405 on UHF.
I since built the ETF band 1 modulator, as referred to further up this thread, which works quite well. There are many other variations that have been published over the years. Sync can be a bit critical at times - some sets cope with it better than others. Ultimately, I'd think a separate sync source combined with the video from the computer would be better. Still, it's good fun, and is good for playing CDs, and watching off air programmes via the digital tuner. I use a USB stick with MythTv, which works well. Look forward to seeing some pictures..
__________________
John |