RG-59 seems to be the standard small (0.25 inch) 75 ohm coax - however, different makes may be of differing qualities.
RG-59 seems to be the standard small (0.25 inch) 75 ohm coax - however, different makes may be of differing qualities.
-- Peter Bennett, VE7CEI peterbb4 (at) interchange.ubc.ca new newsgroup users info : http://vancouver-webpages.com/nnq GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver.powersquadron.ca
Check out
GG Always make NEW mistakes.
From what I have read, RGB video cables are 75 ohm impedance. However, I have never seen a recommendation for the RG number (or other qualifier). I am looking for a good quality cable as we want to go about 15ft with the signal. (Moving a monitor from one part of our lab to another.)
Any suggestions, recommendations, links to FAQs, etc, etc will be greatly appreciated!!
Thanks!
Don
RG59. Belden 1426A has 8.5 dB/100ft loss at 1 GHz.
Alternately, RG6. Belden 1694A is 5.9 dB/100 ft at 1 GHz.
If you can't find those, just pick up any old RG59 at Radio Shack or Fry's and try it.
Good luck.
John
Probably RG-6 would do the job -- cheap and reasonably low loss.
-- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form che...@prodigy.net.
First of all, "Thanks!" to everyone who has commented so far! Your insights have been extremely helpful.
Some additional info for things that folks have had to make assumptions about:
The signal is an RGB video signal with sync on green (i.e. there are only three outputs - RGB - from the video card to the monitor.
The system is an old DEC Alpha VME system. I have not been able to dig up any info on the video output. General consensus in the lab is that the display is running at 1280x768, but since the system is currently down for maintenance, no way of really checking.
The monitor is a DEC 21" VRCX1-WA with RGB and high density DB15 inputs. Obviously, we are using the RGB inputs. The monitor it self is spec'ed at
1600x1200 at a 75Hz update rate. This should give the upper end of the video bandwidth, but I am not sure how to convert it into an equivalent video bandwidth in MHz.Right now I have got my hands on some double shielded RG-59 and looking for some 75ohm BNCs. Our lab has a boat load of 50 ohm stuff, but one poster's comments about the connectors being the weak link have me real concerned and I am going to try to minimize any impedance mismatch. Unfortunately, the video card end is a basic DB-15 (not the normal high density type used for PC video).
Again, thanks for the help!
Don
I
You could look for a monitor extension cable:
Good Luck! Rich
That's an odd size, 1280x1024 or 1024x768 would be normal.
1600 x 1200 x 75 = 144e6That's a maximum pixel clock of 144MHz.
You'll be glad of that when you solder your RG59 to it, the high-density DE-15s are a pig to solder conductors that thick to.
Dave.
Actually, the pixel clock rate may be closer to about 190 MHz.
A typical raster scan monitor uses a horizontal retrace blanking time that is typically 20% of the total horizontal line time. In this particular case the monitor would need 2000 pixel clock cycles/line (1600 Active and 400 Blanking). That takes the clock rate up to 180 MHz. Adding in some additional blanking time for vertical retrace and you are close to a 190 MHz dot clock
-- Chuck Wozniak
David Jordan wrote:
Thanks to everyone who responded!!
Looks like I am going to go the RG-59 cable with BNCs on one end and the DEC DB-15 on the other.
Don
IUsed about 18ft of RG-59 and BNCs and it works!
DEC
Igreatly
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.