Question: Losing channels when strong signals are present

Radioman447

DTVUSA Jr. Member
#1
I have Magnavox Converter box. I also have a directional antenna(VU-75XR) on a rotator in the attic with a 10 DB signal injector. When I am picking up distant stations during a band opening if I point the front of the beam in the direction that Most of the skip channels are coming from the converter box will pick up nothing. Not even local channels. I will do a scan and it will pick up nothing. I can then rotate the antenna 45 degress and pick up local channels. I I rotate it 180 degrees on the back of the antenna I will be picking up skip channels from the direction that the skip is coming from. My question is will strong signals cause your converter box to pick up no channels during a rescan or does it sound like there is a problem with my converter box it did not seem to do this until the big solar flares we had a few months ago came along. It did not do this last year
Any advise would be helpful
Radioman447
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#2
Radioman447,

I wonder if your Magnavox converter box is being overloaded by your signal injector (amplifier). Too much digital signal will appear on your screen the same as not enough signal ... no picture. If you are on the threshold of overloading your converter box, your channels could come and go, but having this happen to more than one or two channels is odd. Another possibility is your antenna is capturing a level of multipath that is just above the noise floor and your amplifier is raising that level high enough to be confusing your converter box. You could test by removing the signal injector from your setup to see if this restores dependable local station reception.

Regarding distant stations received from the rear of your antenna, is it possible there is a reflector (tall building, mountain, etc.) that is the 'actual' source of those signals and the antenna is behaving as it should? Although not DX, I use a home-brew 12-bar cut-to-channel Yagi to capture a reflected signal coming from one local station that is reflected from something (probably a skyscraper) located in downtown Seattle.

Jim
 

MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#3
I have a U-75r (similar to the UHF section of your VU-75XR, only larger) and I do pick up a strong signal off the back of it. I use it to my advantage, since I have towers 10 and 30 miles distant in opposite directions.
 

Radioman447

DTVUSA Jr. Member
#4
I will try that Jim. I appeciate your quick response. I did not get the rotator untill August of last year so I had a comprimised position for the antenna untill then. But last year I never had anything like this occur even after I got the rotator.
Radioman447,

I wonder if your Magnavox converter box is being overloaded by your signal injector (amplifier). Too much digital signal will appear on your screen the same as not enough signal ... no picture. If you are on the threshold of overloading your converter box, your channels could come and go, but having this happen to more than one or two channels is odd. Another possibility is your antenna is capturing a level of multipath that is just above the noise floor and your amplifier is raising that level high enough to be confusing your converter box. You could test by removing the signal injector from your setup to see if this restores dependable local station reception.

Regarding distant stations received from the rear of your antenna, is it possible there is a reflector (tall building, mountain, etc.) that is the 'actual' source of those signals and the antenna is behaving as it should? Although not DX, I use a home-brew 12-bar cut-to-channel Yagi to capture a reflected signal coming from one local station that is reflected from something (probably a skyscraper) located in downtown Seattle.

Jim
 

Tim58hsv

DTVUSA Member
#5
When the skip phenomenon is happening I usually lose a couple of the weakest OTA channels too but the strong ones still come in. It's probably like Jim said and the amps are overloading the receivers.
 

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