CurtPalme.com Home Theater Forum

[gjaky]

An inch of single wire has an inductance of about 20nH, a coaxial cable might have less inductance but I bet it is in the same ballpark as its capacitance.

[redfox001]

[redfox001]

Well I took the trouble of ordering 30m of the best RG6 I could find and was affordable. Three times shielded and 100 meter would be 18db down at 1GHz. So 1 db for 5 meter at 1 GHz. If it acts as a transmission line it will be an almost flat response.

Also a connector to the VGA without any cabling or stray capacitance.

So I must have a comparable setup as Casey.

And all of that in the name of science I do believe there is something special happening here and the fact that I could not immediately reproduce it can be explained by the exceptional setup so I took exactly the same length cables and that I believe might be the most important parameter. At 50MHz the wavelength is around 6 meter so above that we might get a transmission line behavior just not very much. I can't wait to test this

[redfox001]

Ok I tried again with bad results. I have a high quality rg6 vga to bnc cable of 6 meters just like Casey.

It still shifts the image vertical on 1080p on 720p the image was a little better and more stable but on both the bandwidth was nowhere near the screenshots that where placed here.

I remember Francisco wrote in the Eisemann thread that he tried too with coax soldered to the vga card and got nowhere near these results.

To conclude it is a complete mysterie and I am a little pissed that I had to spend another 50 euro on this

[redfox001]

This is what Francisco wrote on the topic

[redfox001]

I still will not give this up. My next idea is that it has to do with the implementation of the Nvidea chipset. Mine is an Asus GTX750ti. Casey's is a Gigabyte. Perhaps the analogue stage is different filtered.

So I am going to try a cheap Gigabyte card. Anyone have experience with Gigabyte that confirms this like 'he I had great results on that ... and I used a Gigabyte too'?

[gjaky]

[redfox001]

Good tip the scope. I'll look for one.

But how do you explain Caseys one on one picture if it was not the graphics card because everything else is the same as far as I can think of.

It might even explain why you don't get the bandwidth out the Nec where Casey does. Perhaps you don't use the same vga card? Or did you use a generator for the signal? Hmm you probable measured after the vga and everything was ok?

Wat is strange with mine is that they also show bad one on one on the Marquee while the Marquee even has MP mods I can not understand that the Marquee would also have a problem with bandwidth. Therefore I keep thinking it must be the vga card.

[redfox001]

He I am thinking could it be that the configuration parameters like anisotropic filtering x times and anti aliasing etc also work on the analogue output?

@Casey how did you fidle with these configuration of the digital filters?

[CasetheCorvetteman]

I leave all those on default.

[redfox001]

Ok but there is some procedure to optimise the system. In my case all these buttons are disabled because my motherboard is very old and I have only 1 GB memory.

[CasetheCorvetteman]

I have set them all up at max settings before, couldnt really see a difference in movies with it.

Ive got 4 gig video card memory and 32 gig system memory, not that i think itll matter much in this case.

[gnnash]

Those settings have absolutely nothing to do with video playback. They are only used for 3D rendering, like when playing games.

[redfox001]

Indeed they do nothing.

The only facts I found after trying 1080p from the 750ti on the Cine 9 and on the Marquee with mods is that the Marquee resolved the bandwidth much better but not 100%. So I don't know if the vga is not 100% or the Marquee is not 100%.

What are the experiences with the Marquee without mods does it resolve 1080p 100% from a Moome?

Also the image from vga is very stable. No jitter and I see little noise but I only looked at testpictures, no movies.

Seems to me the vga card is a great solution for video playback. It looks great.

[CasetheCorvetteman]

[CasetheCorvetteman]

[Melifluonze]

Ok, so this is ancient stuff...

I used to run an ATI Radeon card back in the day, with a Faroudja chip-based scaler in another slot of the HTPC. I always had a problem with signal quality going through 25 feet of coax to BNC inputs until I purchased an Extron 203 Rxi (or equivalent).

These things accept a VGA input (15 pin DIN plug) and output RGBHV. They DO NOT scale or modify the image, but they do display the frequency (dot clock) and they allow you to peak the interface (adjust the signal level and impedance to match the line you are driving) and they allow you to move the image in the x and y direction.

The peaking part of it REALLY improved my image by removing the ringing on the edges of everything...

Is that something you guys need? If so, there are several versions of the Rxi boxes. They are super cheap now ($25 on ebay), you just need one that has the dot clock bandwidth capability you are looking for.

This is a link to the 203 Rxi manual:

http://media.extron.com/download/files/brochure/rgb_203_rxi_bro_revA.pdf

You keep the VGA to VGA cable short (from PC to Extron box) and then drive the long BNC to BNC cable to the projector. And then peak the thing out.

Does a nice job...

[ecrabb]

Hey, Case… I don't mean to thread-crap, but would you mind chiming in on my old thread where I'm asking about video cards? Thanks!

http://www.curtpalme.com/forum/viewtopic.php?p=420999#420999

SC

[CasetheCorvetteman]

No problem at all Crabb, you know things like that dont bother me

Ill take a look shortly.

[CasetheCorvetteman]