View Full Version : OTA ATSC Audio Drop Outs


acesk8er
06-23-09, 10:37 PM
I live in South Florida, the lightning capital of the world, in an area with a couple of high band VHF TV stations. I'm only 10 miles away from the transmitters and both stations are high powered, more than 50 kW ERP each. I'm watching with a Zenith DTT-901 CECB and an indoor "rabbit ears" antenna setup. The Zenith's signal meter is pegged at almost 100% most of the time with some minor variations.

We've had some pretty severe thunderstorms roll through today. The audio on the VHF stations drops out every time there is a lightning flash, it is VERY ANNOYING and the result is that the programs they are showing are, for all practical purposes, unwatchable. No problem at all on strong UHF stations...

Question: Is there a CECB or receiver that has better error correction or that just does a better job of masking audio drop outs? (Analog NTSC has FM audio so the video would get sparkles but the audio was hardly ever affected by lightning, I'm looking for a similar digital experience.)

D-6500
06-23-09, 10:48 PM
I live in South Florida, the lightning capital of the world, in an area with a couple of high band VHF TV stations. I'm only 10 miles away from the transmitters and both stations are high powered, more than 50 kW ERP each. I'm watching with a Zenith DTT-901 CECB and an indoor "rabbit ears" antenna setup. The Zenith's signal meter is pegged at almost 100% most of the time with some minor variations.

We've had some pretty severe thunderstorms roll through today. The audio on the VHF stations drops out every time there is a lightning flash, it is VERY ANNOYING and the result is that the programs they are showing are, for all practical purposes, unwatchable. No problem at all on strong UHF stations...

Question: Is there a CECB or receiver that has better error correction or that just does a better job of masking audio drop outs? (Analog NTSC has FM audio so the video would get sparkles but the audio was hardly ever affected by lightning, I'm looking for a similar digital experience.)

As long as the digital spectrum continues to occupy a portion of the AM-errr, ehh, VHF - band these problems will continue to manifest. All it takes is a paper and pen or a PC and for people to write the FCC with all the complaints they are posting on AVS Forums, Google Groups, & elsewhere, and things will change - slowly - but they will.

acesk8er
06-23-09, 11:07 PM
As long as the digital spectrum continues to occupy a portion of the AM-errr, ehh, VHF - band these problems will continue to manifest. All it takes is a paper and pen or a PC and for people to write the FCC with all the complaints they are posting on AVS Forums, Google Groups, & elsewhere, and things will change - slowly - but they will.

I agree with you that obvious problems like audio dropouts should have been vetted out long before the very capable but also problematic ATSC system was foisted on an unsuspecting public. But at this point the barn doors are wide open and the horses are long gone...

Is there a TECHNICAL solution to this problem? Better and stronger FEC for the audio stream? A receiver that repeats audio packets to compensate for dropouts?

R Johnson
06-25-09, 08:55 PM
Audio dropouts were very bad with early generation ATSC tuners -- whether on VHF or UHF frequencies. The latest generation tuners are far better. That suggests that even better tuners might be able offer improvements in this regard. (I have not followed tuner developments recently, but I've never seen any boxes claiming improved reception.) The parameters for the ATSC audio stream appear to be etched in stone.

The ATSC Mobile option being developed may very well offer improvements here, as it uses lots of extra bits to assure that enough bits can be successfully received in a mobile environment. However this cannot be received by any current STBs or TVs. Any bits devoted to a mobile stream are taken away from the present signal. This could seriously hurt the ability to transmit a high quality HD signal. Given antenna dimensions, VHF stations would seem to be at a disadvantage to UHF stations for mobile reception, especially for hand held devices.