sattech2000 0 Posted January 26, 2009 Afternoon! Need some advice from experience. Need to try and get this right on the first order I place. I have a 4ch dvr being modulated with a 4ch Channel Plus Modulator. That is being feed into a channel plus 8200 amplified distribution block. When the cable was installed (fed to the 8200, basic cable only) the Modulated channels turn very fuzzy. The cable CO looks fine. From what I understand, correct me if I’m wrong, is the cable line coming in is very hot overpowering the modulated channels. I figure I need a notch filter but haven’t found one for four channels. Any advice there? Also should I consider trying to amplify the modulated channels or some type of filter on the cable line? Any tips or suggestions are greatly appreciated. Thank you Share this post Link to post Share on other sites
scorpion 0 Posted January 27, 2009 Diagrams and Layouts http://www.channelvision.com/files/guides/diagramsLayouts.pdf Filters and Digital Cable Support Guide http://channelvision.com/files/guides/Filters_And_DigitalCable.pdf http://www.channelvision.com/ http://channelvision.com/ Affinity Digital Cable Combiner http://www.channelvision.com/products/index/88 http://www.channelvision.com/products/view/427/88 http://beta.channelvision.com/uploads/1215557281_P-0321_MixedSystem.pdf Share this post Link to post Share on other sites
sattech2000 0 Posted January 27, 2009 are you saying i'm not going to be able to make my current system work? Share this post Link to post Share on other sites
scorpion 0 Posted January 27, 2009 No. I just do not know what components you have used to set up your "system". You know your system better then I do. I thought I would give you the "shotgun" effect, and see what pellets "hit the tree". I can relate to what you are saying about the cable feed being stronger then your modulated system. The modulator should have a variable screw/knob to adjust the modulated feed. You need to add "gain" out of the modulator, and you need to make the modulated signal stronger than the cable feed. Think of it as a Teeter Totter. You have to balance the two signals. Do you have a CVT 15PIA in the system? This goes between the cable feed, and where you "mix" the two signals. You turn this amp down to match the modulated signal. The tricky part is getting the teeter totter perfectly balanced. Is there anything here that can get your system up, and running? http://www.channelvision.com/files/products/1215042484_CVT1stereo_CVT1ub_CVT2ub_CVT3ub.PDF If you have any BNC T's in the camera video cables then you may create distortion. I am not saying you are having this problem, There may be people who come to your post from a search engine, and I just want to add this in. I have found T's where the signal is split from the camera with a BNC T. One split goes to the DVR input, and the other goes to the modulator. I find this with the kind of DVRs that do not have loop through. Once you have the CVT 15PIA in to the circuit, and get it balanced then you should be good to go. If you have digital cable, or high def then you cannot modulate the system. It will kill the digital signal, and you will lose Hi Def. It will kill the on demand channels also. Do you have a buddy who is a cable installer? Can you borrow is RF meter? This will help get the two branches at the same signal strength. Share this post Link to post Share on other sites
sattech2000 0 Posted January 27, 2009 Thank you for taking the time to help me on this. I will try to explain the current setup better. Currently I have three cameras that go to a four channel modulator. http://www.channelplus.com/product_detail.php?productId=101 the modulator is capable of doing pass through, however I have to use the T-BNC splitters and remove a jumper on the unit to enable this feature. I’m guessing the jumper is to not terminate or something like that. Then the lines feed the DVR unit from the T-BNC. The DVR Quad output is then fed back to the fourth modulated input. The modulated output is run to an 8 port bi-directional Rf Distribution Amp. http://www.channelplus.com/product_detail.php?productId=59 The distribution amp has an input for the cable company and two inputs for modulated options (The combiner) and then distributes to 8 TV’s. I’m only using one modulated input although I tried both inputs with the same results. I would have to check again to make sure, but I’m fairly certain the DVR recording (which is after the modulator using the BNC T’s) is not affected. Also when the cable line is removed the modulated channels look great. I believe this would point the problem to the difference in signal strengths between the modulator and the Cable Company. However I’m not certain of this and that’s why I’m here asking you experienced guys. I have to place an order tomorrow and have it overnighted for a Wednesday delivery so I want to make my best educated guess on what to order to fix the problem. I read another post, which I think you wrote, explaining the teeter totter affect. That makes a lot of sense and is where I got the idea of the problem being a difference in strengths. My ideas to fix the problem would be a notch filter, that would blank out the Cable Channels. But I’m not certain that would entirely fix the problem and haven’t found one that would give me the ability to have four modulated channels. I did find a band pass filter that would block out everything above channel 90(I think it was). But would that affect the HD signals? The cable service is basic cable, no set top boxes, but does have some HD channels. And/Or should I try to get the two signals to be relativity matched? And what exactly would I use to decrease the cable co signal or do I just increase the modulator to match the Cable strength? I might have access to a strength meter but not the knowledge to go along with it(long story and I should know for sure tomorrow). Again thank you for any ides you might have on this problem. It’s helping me out a lot. I’m getting into doing this stuff and kinda got burnt on the $180 distro amp that I thought would fix the problem. Randy Share this post Link to post Share on other sites
coolie11 0 Posted January 27, 2009 Add a NF-471 to the Cable feed and set your modulator above 100 skipping 2 channels, eg:- 100, 104, 107 & 110. and you should be good to go. What's happening is, you're suppling the system with 2 feeds alike (within the same frequency and channel line). Share this post Link to post Share on other sites
sattech2000 0 Posted January 27, 2009 the one you recommended won't work according to the specs I found. Am I missing something? This one will only give me two modulated channels with a once channel spacing. NF-471 Specs Rejects CATV channels 75 to 80 Allows insertion of CATV channels 76, 77, 78, & 79 Share this post Link to post Share on other sites
coolie11 0 Posted January 27, 2009 You're right. You should be using the LPF-600. Sorry about that, I didn't pay attention to the details, I only use Channel Vision Equipment. Share this post Link to post Share on other sites
sattech2000 0 Posted January 27, 2009 I think I might be better off using two filters. NF-470 and NF-471. That way I won't mess with any of the digital channels above channel 100. The NF470+NF471 would block out channels 70-80. See any problems with that? Share this post Link to post Share on other sites
coolie11 0 Posted January 27, 2009 Add a NF-471 to the Cable feed and set your modulator above 100 skipping 2 channels, eg:- 100, 104, 107 & 110. and you should be good to go. What's happening is, you're suppling the system with 2 feeds alike (within the same frequency and channel line). Share this post Link to post Share on other sites
