problems with reception when using a new DVD?DVR

I just bought a new DVD/DVR. It's a Magnavox MDR867H. My old unit was a Toshiba 670. I have OTA reception.
I have a Winegard 1080 outside antenna installed.
I've had problems with reception of my local NBC station before. This antenna fixed it.
With the new DVD/DVR I'm again having problems.
I can receive TV fine, but when I record on this channel the playback is distorted. This is what happened with the previous unit, but the antenna fixed it.

A few thoughts....
Should I shorten my coaxial cable?
Do I need to amplify the antenna?
Do I need a new antenna?

Thanks for any thoughts.