PC causing TV inteferance - Page 1
Forum section: electronics / rf-microwave

author: Avi
author_rank: Contributor
timestamp: June 15, 2017, 12:19:29 pm
content: I'm in Melbourne Australia, and my PC seems to be causing a large amount of interference on all of the nine networks digital TV stations (and possibly others to a lesser extent).it effects both the main TV, and also my USB TV tuner.Here is my PC spec:Intel Core i7 4790K 4.0GHz (4.4GHz Turbo) Quad CoreBe Quiet! Dark Rock 3 CPU CoolerMSI Z97-GUARD-PRO MotherboardBe Quiet! Pure Power L8 600W Power SupplyDeepcool Tesseract SW USB 3.0 Mid Tower Chassis Black/BlueCorsair Vengeance Red CMZ16GX3M4X1866C9R 16GB (4x4GB) DDR3Samsung 850 EVO Series 500GB M.2 SSD (M.2)Seagate Barracuda 2TB ST2000DM001Gigabyte GeForce GTX 970 G1 Gaming 4GBPioneer BDR-209DBKS 16x Blu-Ray Writer BlackMicrosoft Wired Desktop Keyboard 600ASUS PB278QR 27in Widescreen IPS 2560 x 1440 Monitor with cables and speakersICY BOX 5.25in Multiport Panel with Card ReaderTP-Link TL-WDN4800 450Mbps Wireless N PCIe Adaptor (802.11a/b/g/n)Targus Bluetooth 4.0 USB AdapterNote, the side of the PC case has a transparent window (I don't know if that is relevant), I have tried covering it with foil, and grounding it. It completely obliterated CH9 reception!Sometimes the position of where I am standing near the PC can improve the reception.If i connect the audio output of the motherboard, to the front panel audio jacks (see icy box above), and then plug in the headphones, this greatly degrades CH9 reception even further. However, if i connect it to the case's inbuilt audio out jacks at the top, and then plugin headphones, the interference is not increased as much.I'm not sure what is going on here, or how to solve it. Ideally, the reception should work without, and with headphones, and regardless of socket used.so in short:PC: interferencePC with foil: massive interferencePC with front headphones connected: a lot of interferencePC with top headphones plugged in: a bit more interference then no headphonesPC with person standing in the right position nearby: interference reducedPC off: reception is fine.It changes from day to day, and even time of day, and seems to have nothing to do with how loaded the PC is, even while idle the effect is the same.

author: P90
author_rank: Frequent Contributor
timestamp: June 15, 2017, 12:28:02 pm
content: I'm betting on the transparent case cover...

author: X
author_rank: Regular Contributor
timestamp: June 15, 2017, 12:30:55 pm
content: Is the TV's RF input wired to a wall socket or a separate antenna?Are you able to test this with another PC or even just swap out the PSU? The main culprit I can think of is EMI being sent back into the mains as a result of the high-frequency switching within your PSU (bad internal EMI line filter?)Also try turning off the PC monitor or change its refresh rate to eliminate the possibility of EMI from the monitor. What sort of monitor do you have?

author: cdev
author_rank: Super Contributor
timestamp: June 15, 2017, 12:31:44 pm
content: Get a bunch of ferrite cores and put them on all cables, also check BIOS settings. Yes you need to cover the hole.

author: Muttley Snickers
author_rank: Unknown
timestamp: June 15, 2017, 12:40:10 pm
content: I'm betting the antenna, cabling or connections are questionable, as X has already asked please give us an over view of the antenna arrangement.I'm also in Melbourne and was an antenna installer for 20 odd years, don't do much of it nowadays but still know a thing or two and still have all my test gear.

author: wraper
author_rank: Unknown
timestamp: June 15, 2017, 01:01:30 pm
content: Try changing the cable connecting PC and monitor. And not by cable from ebay. You could also just try changing resolution, therefore pixel clock and interference frequencies will change. Just be sure to verify actual resolution in the monitor OSD as sometimes scaling happens in the GPU, not monitor.

author: DimitriP
author_rank: Super Contributor
timestamp: June 15, 2017, 04:18:34 pm
content: QuoteEspecially on the audio header cable feeding the "front" and "top" headphone jacks.If the PC will still function without it, try it with the cable feeding this top and front headphone connection disconnected from the motherboard.If this is a new build, remove the motherboard and scrape off the powder coating/ paint from the case's motherboard mounting points.

author: dmills
author_rank: Super Contributor
timestamp: June 15, 2017, 04:20:30 pm
content: When you covered the hole, did you make sure there was direct metal to metal contact all the way around the perimeter (Also between the various case panels)?Gamer style PC cases are notorious for not getting the metal to metal contact thing right, and any time you have a slot, you have a potential radiator (The slot acts as a resonant antenna).Check for cable radiation, an E and H near field probe is useful if you have access to a SA (Also good for checking for slot radiators), but even a UHF scanner can be used in a pinch. Check that the IO shield is making good contact all the way around, and check that the motherboard has at least one metal mounting stud so that it is bonded to the chassis, add clip on ferrite on any cables that show common mode radiation.Failing all that throw the system back at whoever built it as unfit for purpose, they chose the parts they should be certifying the EMC performance.Regards, Dan.

author: P90
author_rank: Frequent Contributor
timestamp: June 15, 2017, 05:31:27 pm
content: why do you think OEM cases like Dells etc have such well shielded cases with plenty of grounding fingers on all the case parts...

author: Avi
author_rank: Contributor
timestamp: July 01, 2017, 12:19:43 pm
content: Quoteseperate antenna, but I imagine the grounds are linked?Quoteantenna>splitter>TV and PC tv tunerQuoteno just in 1 spotWell the company does not seem to sell case sides only!the only option is to debuild the entire pc and put it in another case, the closest they say they have without a window (it has an air grille there instead) ishttp://web.archive.org/web/20150401131724/http:/www.pccasegear.com/index.php?main_page=product_info&products_id=29393&cPath=547Do you think it would be suitable?

author: BigBoss
author_rank: Regular Contributor
timestamp: July 01, 2017, 04:02:14 pm
content: I think the antenna input is connected with a poor shielded cable ( or cable is damaged,stripped etc.).The TV can also be interfered directly from the Motherboard or via electrical network but their possibilities are relatively low.Using a well shielded cable and tightly crimped antenna plug will resolve the problem.

author: Avi
author_rank: Contributor
timestamp: July 23, 2017, 01:21:44 pm
content: changing between DVI and quality HDMI makes no difference, I can even cause it to happen (sometimes) by just running a cryptocurrency miner (which has nothing to do with video output cables).If i remove the video card altogether, and use the onboard video, then the TV reception becomes fine, and my pc tv tuner goes from no reception at all to really bad reception.should i replace the power supply? the video card? the computer case? all? something else?

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 24, 2017, 04:24:31 am
content: Get a RTL-SDR and make a simple near field probe for it. Then you can zero in on the culprit.Also try switching the spread spectrum settings in the BIOS. (Enable it if disabled and vice versa.) That it interferes with OFDM indicates the noise is either very strong or broadband in nature.

author: stj
author_rank: Super Contributor
timestamp: July 24, 2017, 05:11:23 pm
content: it sounds like your radiating from the groundplane!completely check your house earthing from where it enters the house all the way to the socket, the power cable, and the pc psu.i assume you tried without the monitor plugged in?

author: D3f1ant
author_rank: Frequent Contributor
timestamp: July 25, 2017, 06:03:12 am
content: I had something similar but with audio, everytime the gpu/cpu load went up there was audible hissing. Long story short, by process of elimination it turns out the expensive but pretty all alloy case was the problem. Replaced it with cheap china steel case and ALL my noise problems went away.