# Helicopters and OTA? WTF?



## Sir_winealot (Nov 18, 2000)

The wife was watching Ellen the other day and called for me to come look at the picture. It was dropping out pretty badly every minute or two.

At the same time, there was a helicopter going back and forth behind my house. I checked the signal strength, and each time the chopper went by, the signal strength dropped from 90 down to near zero.

This went on for nearly 5 minutes.

Once the helicopter left the area, the problem stopped and our signal went back to a solid 90. 

How is it possible for this to happen?


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## bpdp379 (Feb 25, 2004)

When I lived in Seattle, our local ABC channel used to get three equally spaced signal drops of about five seconds each beginning at about 8:10 PM every Wed night. After months of troubleshooting by the station it was found to be a Navy aircraft doing electronic signal jamming. They changed their freqs for training and the problem went away.

Do you know the kind of helo? Military or civilian?


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## JimSpence (Sep 19, 2001)

Sir_winealot said:


> The wife was watching Ellen the other day and called for me to come look at the picture. It was dropping out pretty badly every minute or two.
> 
> At the same time, there was a helicopter going back and forth behind my house. I checked the signal strength, and each time the chopper went by, the signal strength dropped from 90 down to near zero.
> 
> ...


One word - Multipath. Causes ATSC tuners to lose signal loss.


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## Sir_winealot (Nov 18, 2000)

bpdp379 said:


> Do you know the kind of helo? Military or civilian?


It was definitely civilian.



JimSpence said:


> One word - Multipath. Causes ATSC tuners to lose signal loss.


Jim, so you don't think it had anything at all to do with the helicopter, or are you saying that the signal was somehow being bounced while the thing flew between our house and the signal source?

The only other time this happens, is when we gets storms and high winds....it's the equivalent of OTA rainfade.

Since there are so many trees here, I figure that the winds are blowing tree branches around that are messing with the signal ....causing multipath. But I didn't think that rain/clouds would affect the OTA signal like it does a satellite signal?


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## phox_mulder (Feb 23, 2006)

Sir_winealot said:


> Jim, so you don't think it had anything at all to do with the helicopter, or are you saying that the signal was somehow being bounced while the thing flew between our house and the signal source?


Big chunk of metal between you and the "line of sight" transmitters.
Yes, bounced the signal around enough that your tuner lost lock.

phox


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## Markman07 (Jul 18, 2001)

Are you by Area 51? /jk


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## Lije Baley (May 12, 2004)

Back in the sixties (when I was a teenager) we lived about 40 miles from SF and on the east side of the hills in Contra Costa County. We got our five stations from SF and three or four from Sacramento with an antenna mounted on a forty-foot high mast. Our area must have been on the flight path of one of the Bay Area airports. Many planes would pass over several thousand feet above the house. Every time one did, the television signal would deteriorate. Obviously, the planes were not blocking the signal at their altitudes, but they were reflecting a second signal to our antenna. Your helicopter was creating the same multipath problem, but HD tuners have even greater difficulty with those signals.


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## Billy66 (Dec 15, 2003)

Yep, I'm in a flight path and when a plane comes over the signal will often break like that.


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## bonscott87 (Oct 3, 2000)

Yep, it happens. I live about 2 miles north of an airport and landing planes will go right over my house when the use the north runway. OTA signal will dropout and freeze for a couple seconds when that plane goes over. Luckily it's a smaller regional airport so it doesn't happen often.


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## ipfreely (Sep 16, 2005)

UNIComm is nasty.


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## JimSpence (Sep 19, 2001)

IOW, the helicopter's blades caused multipath.


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## smarsh66 (Apr 17, 2004)

JimSpence said:


> One word - Multipath. Causes ATSC tuners to lose signal loss.


100% agree..... i've had the same happen when a small airplane flys overhead.... just check you signal meter when you experience this and you will find it bouncing all over the place.... multipath!


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## TyroneShoes (Sep 6, 2004)

It may also be the transponders on the aircraft which can pulse RF that can interfere with reception, although this is more likely to affect sat reception than OTA (frequencies are closer). Most commercial antennae farms have to install filters for this very purpose.

I once had a similar situation as a cable headend tech in Galveston, TX. One day a Navy ship docked (fairly unusual) and its radar glitched every channel on our system for hours, interfering with sat reception directly. Not our best day.


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## TonyD79 (Jan 4, 2002)

How low was the chopper? Could it have been blowing trees around? Since you get multipath when the wind is high.

This has been an issue with OTA even back in the analog days (like that was so long ago). Planes going overhead causing ghosting and shifting and audio buzz. The signal is still on analog carrier even though the data is digital. The interference just manifests itself differently.


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## jap3 (Jul 14, 2003)

smarsh66 said:


> 100% agree..... i've had the same happen when a small airplane flys overhead.... just check you signal meter when you experience this and you will find it bouncing all over the place.... multipath!


Corbin Dallas, Multipass!


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## Sir_winealot (Nov 18, 2000)

TonyD79 said:


> How low was the chopper? Could it have been blowing trees around? Since you get multipath when the wind is high.
> 
> This has been an issue with OTA even back in the analog days (like that was so long ago). Planes going overhead causing ghosting and shifting and audio buzz. The signal is still on analog carrier even though the data is digital. The interference just manifests itself differently.


Nope, it wasn't low enough to have blown the trees. I just found it amazing that the thing could actually interfere with the signal each time it made its' pass. When I told my wife "it's the helicopter," she was like..."yeah....right." LOL


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