This might be of help to you:
Can I continue using my existing VCR with a DTV converter box for timed recordings?
Yes. However, after the digital transition, the tuner in the VCR won't be able to pick up over-the-air programs for recording. Instead, the input to the VCR must be connected to the output of the DTV converter box. You must set the tuner in the DTV converter box to the channel you want to record prior to the start of each recording period programmed in the VCR.
Source: http://dtvanswers.com/dtv_converterbox.html (05/29/2008)
I just found this link by accident...it might have what you need:
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