I'm trying to hookup my Toshiba DR430KU to an older tv that require an RF Modulator. I get a skewded sideways picture. Does This DVDR compatable with a RF Modulator?
Probably not. Better picture results are achieved with either S-Video, standard RCA AV cable (yellow-white-red), or YUV component cable (red-green-blue) (component output does not have audio - this requires extra cable to be connected). The video via either one of these 'AV' connections is stunning (based on a standard 16:9 LCD TV using a Panasonic DVD recorder).
RF tends to be lower quality - as opposed to AV/digital input. AV input/YUV component handles digital better. No one connects their DVD devices to their TV via RF (either directly to the antenna socket or with a modulator/attenuator) anyway. Because a VCR is mostly analogue, it will work fine with an RF connection, but DVD is digital, and so won't work as well, if at all.
RF also goes through the tuner in a TV, creating cross-interference, whereas AV is a direct input and is separate to the tuner.
I would say an RF modulator would not be designed to handle the output frequency that your DVD device generates. Throw the modulator out, or perhaps get another TV, or use RCA cables instead if the TV has AV inputs. Whichever is cheaper and easier, but don't use RF accessories except a standard antenna if/as required.