Due to a Tower collapse our local PBS station (kozk) which normally covers this area is not. There is another PBS station (kemv) (southwest) which I'm On The Fringe area of I thought I would try to receive. I Custom-made an antenna for RF Channel 13. this evening I connected the antenna for about 35 ft of coax directly to the TV set. The antenna was resting on a railing on a ground floor deck. The desired station came in without any problem and with a good strong signal. so I climbed up on the roof and mounted it at 3 ft above a VHF UHF antenna that I had pointing towards Springfield Missouri (northwest). The height above ground would be about 30 ft. The two antennas went into antenna combiner. That went into a mast Mount RCA preamplifier. At that point all of the channels came in except the one who should previously been the strongest from Springfield. Things were fine for about an hour and then stations started disappearing. Finally all of the stations were gone. My suspicion was the preamplifier since I had not previously used one. I removed it and just hooked into the antenna combiner directly. At that point all of the Springfield stations returned. I lost the PBS Channel though. And in a weird twist started receiving sporadically a channel from Jonesboro Arkansas (rf8). None of the antennas were pointed in that direction at all. I'm also not receiving the local low power station that comes in with no trouble as I'm only a few miles from the transmitter. Now I'm starting to consider there might be some interference between the two antennas. Are there any rules about spacing? Any other suggestions I might try? Thanks!