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Video signal amplifier.

Discussion in 'Audio' started by HANKMARS, Jul 28, 2019.

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  1. HANKMARS

    HANKMARS

    78
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    Jul 28, 2019
    Howdy. The following configuration gives me a gain of 2 and reliable color signal thru 500 feet of spooled cable.

    DSCF2463.JPG
     
    Last edited by a moderator: Dec 20, 2019
    davenn likes this.
  2. HANKMARS

    HANKMARS

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    Jul 28, 2019
    HELLO. Well, not sure if you saw last post. Anyway, a gain of 2 was too much to dampen so I paralleled a 2.2K resistor with the existing feedback resistor which gave me 1100 over 2200 or .5 + 1 for a gain of 1.5. Much nicer. I did have to change my output to ground to 130 ohms to make my color signal stable. I'm guessing that I'm encountering a DC level problem. I guess I'm bulling my way thru it
    Oh contrare hare. My eyes may deceive me but video image seems satisfactory. No apologies for stalling of project for I free lance and work on my own time table.
    . BOARD ASSEMBLY 1.0.jpg
     
  3. WHONOES

    WHONOES

    910
    226
    May 20, 2017
    You shouldn't need the 39R resistor in parallel with the cable otherwise it changes its effective impedance.
     
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  4. HANKMARS

    HANKMARS

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    Jul 28, 2019
    Ok. Good to know. Truthfully, it is there to dump off some gain. Didn't work well enough. I will be cutting the gain to approx 1.1 to 1.2 by changing feedback resistor values. This is my first rodeo with video signal manipulation and I do greatly appreciate your help. Thank you.
     
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    It is unfortunate that you found this particular rodeo about forty years too late. I suggest you find some articles in the Internet archives that describe the "how" and "why" of NTSC analog video. DC levels in the video are extremely important. It was fascinating to play with this stuff in the late 1960s through the 1970s before the digital revolution decimated the analog video market. You can still find the technology (sometimes) on the amateur radio bands but OTA (over the air) analog video is no longer available in the USA, and it's becoming almost impossible to find an NTSC monitor, black-and-white and much less possible for RGB shadow-mask color.
     
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  6. HANKMARS

    HANKMARS

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    Jul 28, 2019
    My best guess is that the DC level was the primary problem. I have no idea when I will work with video signals again. They certainly produce a ghostly trace on the Oscope and are rather hypnotic to watch as one changes the camera input. My previous experience with video signals exists on in tech school where we received elementary info. We were introduced to some lingo, sync pulse, front porch, color burst, blanking, back porch, etc., and were given a cursory explanation. I enrolled in school with intentions of demystifying radio operation but was led down the digital path of micro controllers, which is quite alright, after one considers that in the world of radio, antenna design is a science unto itself. Thank you for your helpful information on my project and the interesting side issues. I am sure that I will visit ELECTRONICS POINT quite often. Best regards
     
  7. Audioguru

    Audioguru

    2,873
    644
    Sep 24, 2016
    Hevans,
    Did you play with NTSC scrambled cable signals like I did?
    1) They suppressed the sync but that was easy to fix.
    2) They made the images negative at random that was also easy to fix.
    My circuit worked well but it was not automatic, I had to turn it on.
     
  8. HANKMARS

    HANKMARS

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    Jul 28, 2019
    No I have not ventured there but it does sound interesting. If time provides, I may very well nose around some in that matter.
     
  9. HANKMARS

    HANKMARS

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    Jul 28, 2019
    I believe that I still have a DC level problem. If camera strains to get an image in low light (practically total darkness) color is lost, even after light is reintroduce. Same goes for a screen white out because of over exposure. Maybe the amp rails out and latches up. Cycling the power will recover the color imaging. I ground my monitor to the power supply at the work station. Actually, I use the negative side of the +12VDC supply. This is 6 volts below what the 811 considers 0 volts but I figured at 500 feet, that the amp would deal with it. Perhaps I should make a voltage divider which to ground my monitor to and see if that makes my amp and its amplified signal more cooperative.
     
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    I suppose the statue of limitations applies for this answer... so, yes. I subscribed to early cable television in the 1960s, provided on poorly-shielded coaxial cable by Time Warner, who has a monopoly on cable TV in Dayton, Ohio. Reception of their frequency-division multiplexed TV channels required a set-top box with a multiple-position channel selection slide switch that translated every available cable channel (about 20 or so IIRC) to either TV channel 4 or 5. Later TVs with digital tuners had the capability of directly tuning to the "free" cable channels, of which there were eventually hundreds, but this feature was not available on my old analog Magnavox TV.

    The "free" channels on the cable were translated "in the clear" without modification of their sync or video polarity. The "pay per view" channels, which included Showtime, HBO and soft-porn channels like Playboy, required sync restoration and color-burst synchronization and perhaps video polarity inversion. Fortunately I was able to discover (after removing the covers and ignoring the warning that no consumer serviceable parts were inside) that all these analog video shenanigans could be easily corrected by moving (or adding) a single jumper wire inside the set-top box. Of course my tampering would have been immediately evident to any technician examining the set-top box, but we never experienced any failures that required on-site repair help. AFAIK my tampering went undiscovered with the roll-out of digital high-definition TV. The analog set-top boxes were then all replaced (and presumably discarded) with new digital set-top boxes, along with increased prices for basic TV services.

    So we reverted to Over-the-Air (OTA) reception with an outside antenna for awhile and canceled our cable TV service. Meanwhile, the Internet beckoned, but data rates were slow over dial-up telephone connections. Eventually, through attendance at a trade show, I got connected with a Detroit company, glasscity.net, who was offering "high speed" ADSL to selected customers who lived closed enough to a central office switch. We had already tried this route with AT&T but they had said we were too far away from their closest switch. Glasscity did their own tests and said they could provide service roughly equivalent to an AT&T T1 line (about a megabit per second). So we bought an ADSL modem and purchased a router with four hardwired ports to connect two personal computers to this new "high speed" Internet connection. Neither my wife nor I missed the garbage programming available from commercial television. There was (and still is) plenty of garbage programming available on the Internet, most of it available for free binge watching from various "on demand" streaming services. Or, if you want commercial-free programming, subscription services are also reasonably priced.

    We stayed with glasscity for several years, but eventually Time Warner upgraded their physical plant and began offering wide-band internet service. They also improved their coaxial cable and the connectors that were used to tie everything together. No more OTA leakage of TV transmitters into the cable network. But we had to purchase a new cable modem that was capable of "bonding" two or more cable "channels" together to achieve up to 25 Mbps symmetrical bandwidth. Our routers were still good to go, but by now wife and I both had lap-top computers, so we needed to upgrade to a wireless router. Good side of this upgrade was we now had 25 Mbps up and down speeds. It stayed that way for several years, sometimes with cable television service but most of the time not, until we retired to Florida in 2016.

    We now have symmetrical 50 Mbps up and down delivered to our home via fiber-optic cable by Frontier, which was formerly Verizon. We declined their cable TV bundle offer and stream video from Netflix, Amazon Prime, HBO, and several other "on demand" Internet video streams. We didn't buy into either the 3D or (later) the 4K video hype but did replace the old Magnavox analog TV with two Samsung wide-screen, flat-screen, 1080p, LCD TVs: one for the bedroom and a slightly larger one for the living room.

    The fiber-optic cable is very reliable, but still requires a "black box" transition from optical signal at the entrance of our house to an electrical signal distributed on coaxial cable inside the house. We also needed a corresponding modem for the broadband electrical signal. I decided to rent the Frontier modem to avoid any "finger pointing" if we ever experienced a service failure. It has been three years now without any problems attributable to the modem, so maybe it's time to purchase our own cable modem and save the ten bux monthly rental fee. Unfortunately the cable modem we used on the Time Warner network will not work with Frontier (or so we have been told) but I keep it around "just in case" we decide to revert to the "other" cable TV company here in Venice, FL. I actually did try them out for a month last year, while waiting for Frontier to replace a fiber-optic cable I accidentally damaged with a shovel while digging up a garden in my back yard. The cable service was okay, and the bandwidth was adequate, but I cancelled after Frontier got the fiber-optic working again.


    I must say it was certainly worth the thirty-something year wait to progress from the NTSC 525-line interlaced scan to 1024-line progressive scan.
     
  11. Audioguru

    Audioguru

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    Sep 24, 2016
    On Black Friday I bought a wide screen "smart" TV from a grocery store (of course they normally do not sell TVs) for about half the normal cost. Also the tax was free and I got lots of "points" to get other goodies later. My cable TV provider charges a fortune for 4K reception and the smart part of the TV has a YouTube button so my son bought me a Chromecast adapter to allow me to see YouTube at 4K for free.

    4K TV is a big change from ordinary old TV because I never had a high definition TV.
     
  12. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    I have been eye-balling the 4K TVs to see if I can see any significant improvement over our current1080p TVs, two of which we bought at truly exorbitant prices (although they were "on sale" at a "discounted" price) about five or six years ago. Prices have come down a lot, but except on screens larger than about 45-inches (diagonal measurement) with 16:9 aspect ratio (so-called "wide screen"), it's hard or impossible for me to see any improvement in resolution. That may be because 1080p lines may be at the limit of resolution for the human eye at normal viewing distances for that size screen. I haven't done any research on that, although IIRC the initial TV scan standard of 525 interlaced lines was judged to be at the limits of human eye resolution for the size CRTs available at the time, again at "normal" viewing distances. Today of course everyone wants to sit very close to the big screen TV so as to immerse themselves in the "action" so to speak, whether that be a multi-player game or watching a movie.
     
  13. Audioguru

    Audioguru

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    Sep 24, 2016
    On my 37" diagonal HD TV I do not see any lines but if I get within 1' I can see the tiny pixels.
    On my 55" diagonal 4K TV I do not see any lines but if I get within 3" I can see the tiny pixels.
    4K is awesome! I have been so close to the 4k screen watching a game all around me that I missed seeing a few goals.
     
  14. HANKMARS

    HANKMARS

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    Jul 28, 2019
    I will, with clear conscience, confess that I, too, abruptly ended cable TV viewing in a large neighborhood area for part of a day. I was installing a cedar privacy fence for a homeowner, myself being an employee of a business named appropriately, The Fence Store. Perhaps loath is not the exact proper term for my emotion whenever fence building became a labor that I had to endure but in all honesty, I haven't the slightest bit of a feeling of accomplishment from fence construction. I suppose I could parallel its rewards to that of having a bowel movement. It's nothing tragic or horrifying, but the best that you can hope for, is just that things go well. A cable tech came by later that day and spliced the cable back together and put a "Scotch Guard" on the connection and gingerly reburied the cable under perhaps an inch of dead leaves and grass clippings. No harm, no foul. It was always a relief to get off fence detail and back to the work that I was hired for. The installation of overhead doors. Garage doors. Purchased from and installed by, The Door Store. Yes, both companies were owned by the same man.
     
  15. HANKMARS

    HANKMARS

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    Jul 28, 2019
    I share your sentiment concerning learning. If one no longer has a desire to find answers to his questions, he is well on his way to mental stagnation and the resulting rot that it will develop. And God am I surrounded by those that can not escape the prison of their own past. Apparently, they are quite content with the idea that they already know everything. One thing the lot of them did memorize, was the creed, If you can't dazzle them with details, baffle them with bullshit.
     
  16. HANKMARS

    HANKMARS

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    Jul 28, 2019
    Well, the finished article is probably at the bottom of an 8" diameter hole, some 400' below grade. I will be building a new remote camera system and will have less limitations on hardware. Maybe use a cat5 cable. A larger spool for less winds on 500'.Two rather radical specs that I wish to meet are 1: The camera enclosure must pass through a 9/16" diameter hole. 2: Directly above the camera, there needs to be a robotic arm. This will be used to aim the view of the camera. I have ordered a camera that resides on a 3.6mm pcb. I am anxious to see what its performance is like.
     
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