The RCA TVPRAMP1R preamp does have a history of quality control problems, but you can buy three of them for the price of one Channel Master 7778. One of the problems is with the separate/combined switch. If you have the switch in the separate position to use two antennas, one for VHF and one for UHF as in your case, sometimes the switch doesn't make good contact with the VHF antenna. The workaround is to use a UVSJ to combine the two antennas and connect the UVSJ to the combined input of the preamp.
http://www.rcaantennas.net/docs/comm...PRAMP1R_OM.pdf
http://voxrightnow.custhelp.com/app/...ramp1r-outdoor
http://voxrightnow.custhelp.com/app/...-pre-amplifier
You should try an FM filter now in the coax between the antenna and the distribution amp. If you mount a preamp near the antenna, the filter should come before the preamp. Two filters to consider:
http://www.mcmelectronics.com/produc...800829%2Cd.eXY
http://www.radioshack.com/radioshack...p/1500024.html
Sorry I wasn't able to give you the magic answer to your problem. Please let us know if you have any success on this same thread.
Best regards,
rabbit