Home Automation - splitting uhf vhf signal from outdoor antenna

i have mant901 51 element antenna. ph61112 preamp. cablerun approx 50 feet from antenna to power injector. channel list is below. 63.1 is actually 12 on vhf and very strong 85-98% in a number of directions antenna was pointed and this is without preamp installed. i installed originally and couldnt pick up signals from virtually all channels. removed preamp and now get most channels but some of the stations further away that i got with old antenna w/preamp (philips 37 element same preamp) are either weaker signal or intermittent in receiving them. i would like to get uhf only preamp but cash is tight for now. is it possible to use an inexpensive splitter that splits uhf vhf signal and split uhf vhf signal just before it enters uhf/vhf preamp and run separate cable for vhf with attenuator for vhf signal and combine after uhf comes thru power source for preamp. my goal is to decrease vhf signal enough and increase uhf signal. will this work? or do i need uhf only preamp? or do you have any other suggestions for inexpensive fixes. these are some channels and distances.

red
uhf WINM 63 IND ANGOLA, IN 148° 19.8 miles 63
* blue
vhf WINM-DT 63.1 IND ANGOLA, IN 148° 19.8 12
blue
uhf WFWA 39 PBS FORT WAYNE, IN 197° 40.7 39
blue
uhf WANE 15 CBS FORT WAYNE, IN 196° 41.3 15
blue
uhf WFFT 55 FOX FORT WAYNE, IN 197° 40.4 55
blue
uhf WZPX 43 ION BATTLE CREEK, MI 4° 68.9 43
blue
uhf WISE 33 NBC FORT WAYNE, IN 196° 41.2 33
* violet
uhf WANE-DT 15.1 CBS FORT WAYNE, IN Feb 17, 2009 (post-transition) 196° 41.3 31
* violet
uhf WANE-DT 15.1 CBS FORT WAYNE, IN 196° 41.3 31
violet
vhf WILX 10 NBC ONONDAGA, MI 30° 57.7 10
violet
uhf WSYM 47 FOX LANSING, MI 25° 57.7 47

The part is called a VHF/UHF diplexer. It splits a single input into two outputs. One output passes the VHF band and the other passes the UHF band.