JOG 0 Posted August 7, 2017 My cctv DVR has EMI issue. I know it’s the DVR unit because I isolated the problem by using a power supply with an EMI filter for both the camera and DRV unit, and only used one camera connected to a five foot RG6 coaxial cable. Can the DVR be fixed, or do I need to buy a new unit? Thank you for your help! Share this post Link to post Share on other sites
the toss 0 Posted August 7, 2017 your fault finding /explanation is a bit short on detail. * Has this setup EVER been working ok? (or is it a new setup) * You say the issue has disappeared with the use of EMI filtering power supply. This could be due to the reconfiguration of your power rather than the EMI filtering properties. This would point to an earth loop problem * Do the cameras normally use a RG6 coax . If so then be aware that RG6 does NOT provide effective noise shielding at CCTV baseband frequencies. It is designed for shielding at digital TV frequencies * EMI filtering via a power supply seems to be a bad joke since EMI (electromagnetic interference) by its very nature is interference induced via the radio frequency spectrum and hence NOT something a power supply will have much influence on hope this information is helpful Share this post Link to post Share on other sites
JOG 0 Posted August 7, 2017 Thanks for the reply. However, I did not state the EMI power supply resolved the issue, it didn't, therefore the problem has to be the DVR itself. The unit is two years old, if it was new I would just send it back to the manufacturer. The 5 foot RG6 cable was used to elimate the existing cables as the possible source, hence the 5 feet. What interference could a 5 foot piece of cable would have to guard against? What I need to know is what component in the DVR could cause this fuzzy view? It's not horrible, but I like to clean it up. Share this post Link to post Share on other sites
the toss 0 Posted August 8, 2017 ............and I did not read it as fixing the problem. I was simply making the point that somewhere there is a salesman laughing his tits off over people buying EMI power supplies Share this post Link to post Share on other sites
JOG 0 Posted August 9, 2017 (edited) I laughed so hard and for so long, I have to say thank you. However, EMI filters are used to remove noise from electric currents that are conducted through wiring and are found in all electronic devices. Whether the power supply truly has an EMI filter, I can only trust the word of the manufacturer. I wish you well. Ciao Edited August 9, 2017 by Guest Share this post Link to post Share on other sites
the toss 0 Posted August 9, 2017 I think a definition of EMI is called for at this point. EMI is electromagnetic interference caused by unwanted EMR which is electromagnetic radiation. Electomagnetic radiation , by its very nature is transmitted in the radio spectrum. Now while it is possible that electrical transmission lines can (and do) act as a ginormous radio antenna, the received signal strength is still in the mV region at best (or should I say worst) and is negligable when superimposed on the network voltage of 11Kv/30Kv. Now that is not to say there is no interference on the mains. You will find lots of switching noise , control tones and arcing - all potential sources of noise in your CCTV system. BUT other than arcing they should not be called EMI. Arcing on the other hand can cause problems over an enormous amount of the spectrum. The first morse code transmissions were simply arc transmitters with a very primitive tank circuit for tuning. If the interference is still there with no cameras OR cable connected then the problem is with the DVR. Modern DVRs are not economical to repair. Maybe a pic of the "fuzzy view" would help Share this post Link to post Share on other sites
