KFDA (CBS) reception trouble. Multipath? Bad tuner?

kareemy · 29-Nov-2015, 4:37 PM

Hi all. Here is the link to my signal analysis results:

http://www.tvfool.com/?option=com_wr...b97d885d913fcb

I'm interested in picking up CBS, Fox, ABC, PBS, and NBC. I installed an RCA ANT751R in my attic and have one coax cable going direct from the antenna to my tv. No splitters, no pre-amps, nothing else.

My TV is a Sony KDL-55W900A. In the Signal Diagnostics menu on the sony, every channel comes in perfect with an SNR (dB) between 28-34. ABC comes in the weakest but still perfect.

The problem lies with CBS which is KFDA channel 10. As I said it comes in perfectly, but then after a while the signal strength drops and starts to fluctuate between 23-25 and a lot of errors crop up. The audio drops out and the picture pixelates. This might start to happen after 10 minutes of watching or several hours and it only happens on CBS.

If I change the channel and then tune back to CBS the signal comes back strong at 32-34 but then after a few minutes or even hours it will drop down again.

I'm new to reception issues and antenna problems so this has baffled me. It sounds like it could be multipath interference especially because the antenna is in my attic. But I'm confused that I can solve the problem at least temporarily just by tuning to a different channel and then retuning back to CBS. Could that indicate that the tuner on my TV may be the culprit?

I've spent hours trying to adjust the antenna and could never get rid of this problem. The issue with adjusting the antenna is that CBS will come in great after each adjustment only to fall back down after a few hours of watching. I'm just looking for some advice or any tips to try to solve this issue once and for all.

Thank you,
Kareem

ADTech · 29-Nov-2015, 5:03 PM

It's interference, either multipath or electronic or electrical noise.

The single most effective thing you can do is get the antenna out of the attic and test outside to see if the reception improves.

Could easily be interference from nearby FM radio stations. If you still have any Radio Shack stores or dealers nearby, see if they have an FM Trap (filter) on hand. Catalog number 15-0024 (or 1500024). Call them personally, do not rely on their website.

kareemy · 29-Nov-2015, 8:05 PM

I thought about putting the antenna outside, but as a last resort. I didn't want to deal with any grounding or weather issues. I may test it outside temporarily and if that ends up fixing it then I'll bite the bullet and do it properly.

I never thought about an FM Trap before. I will try that first and report back.

Today CBS is coming in great, of course. I've left the TV on for 3 hours now and haven't seen any interference. Usually the trouble crops up faster than that but I'm certain it will come back sooner or later.

Thanks for the advice.

kareemy · 12-Dec-2015, 3:23 AM

I just want to post a follow up. I had to order the FM Trap online and it just arrived a few days ago. In the meantime I tried the antenna outside. I mounted it on the roof in the best place I could find. Signal strength was equal or better on all channels vs in the attic. However after just about 30 minutes the pixelation and same symptoms appeared on KFDA.

I put the antenna back in the attic. I installed the FM Trap and placed some ferrite beads on the TV power cord and the coaxial cable. It has been three days and there have been no problems at all. Hopefully that solved it. Thank you, ADTech. It looks like it was definitely some sort of electronic interference.