The rule of thumb is to have a separation equal to at least 1/2 wavelength of the lowest frequency channel of the VHF antenna.
Channel 7 is 174 to 180 MHz.
5540/174 = 31.8 inches
http://www.tvantenna.com/support/tut...combining.html
I think you should be more concerned about Chromstar UHF preamp overload from strong local TV and FM signals than antenna spacing.
http://www.tvfool.com/?option=com_wr...8e03cccd493fef