I have two ATSC receivers hooked up to my TV. One is an Insignia CECB, and the other is a Samsung DTB-H260F.
The CECB is hooked also hooked to my VCR via the L/R audio and composite video. It's hooked up to my TV via the coax.
The Samsung is hooked to my TV via component and L/R audio.

Both tuners are fed by same antenna, via a splitter. Signal strength for both is very good.

Here's the problem I am having. If I have my Samsung powered on, but am watching the CECB through the coax, it looks like a bad analog signal. Some slight snow, lots of fuzzyness. Turn the Samsung off, everything is fine. When viewing the CECB through the VCR (composite from CECB to VCR, the composite from VCR to TV), everything looks fine, regardless of whether the Samsung is powered on or off. So, no worries when it comes to recording.

Now, the obvious solution is "don't use the CECB w/coax when the Samsung is on". But, I still would like to figure out what could be causing the bad picture.

Any thoughts?

The Samsung has an internal amp for passthru - maybe it is overdriving or causing some interference ?

The Samsung has an internal amp for passthru - maybe it is overdriving or causing some interference ?

That was my initial thought, since I originally had the coax running out of the Sammy to the CECB. I thought running both off a splitter would eliminate this, but no dice. I wonder if the Sammy is sending a little bit of power back up to the antenna? I have nothing hooked up to the Sammy coax out.

There may be RF leakage from one box to the other.....
Could be high level oscillator signal feeding the mixer....
or downconverted 44 MHz IF signal.

You could try separating them some more, but leakage path may be via coax.

There may be RF leakage from one box to the other.....
Could be high level oscillator signal feeding the mixer....
or downconverted 44 MHz IF signal.

You could try separating them some more, but leakage path may be via coax.

Aha - me thinks you may be correct. Last night the interference was considerably worse, to the point it was unwatchable. Difference? I had my VCR on. So, RF could have been leaking from the unused VCR and Samsung RF out ports.