Due to the EXTREMELY High FM Signals, you should insert the fol. inexpensive FULL BAND FM FILTER on the Output of the above recommended VHF/UHF Combiner, so it is effective against FM signals picked up by ANY of the three Antennas:
I've never seen an Antenna Model study of the HD-7694P, other than the incomplete charts in W-G's Spec Sheet, which claim a UHF Front/Back Ratio on the order of 20+ dB [i.e. towards 28-deg, for TQ on Ch 26]. HENCE, when pointed towards 194-deg it will be acting as an ATTENUATOR with LOTS OF LOSS [although NOT shown in the spec sheet, this loss could be MUCH, MUCH HIGHER, see discussion below].
Also note that the -3 dB BEAMWIDTH on Ch24/26 is about (or less than) 60-deg. IF UHF Antenna is pointed HALF-WAY between TQ on Ch24 (towards 99-deg) and FOX on Ch43 (towards 149-deg), then EACH would lose 3 dB by being a bit off from the Max Gain point. Since HD-7694P only has about 11.0 to 10.5 dBi Gain (Max) on these channels, you would end up with ONLY about 8.0 to 7.5 dBi Gain respectively on TQ Ch24 and FOX Ch43. Compare that to the 11.0 dBi on Ch24 and 12.2 dBi on Ch43 provided by each of two HDB-4X's when pointed directly towards the desired station:
[This also illustrates the superiority of separate Hi-VHF and UHF-ONLY Antennas vs Hi-VHF/UHF COMBO's.]
Although we don't have an Antenna Model for the HD-7694P [a 5-Element LPDA with 3 Yagi-type Directors and a Reflector SYSTEM], we DO have some Antenna Models that illustrate the EXTREMELY High F/B and F/R Ratios typical for LPDA's, such as fol. 14-Element LPDA that provides roughly same Gain as HD-7694P:
UHF 14-El VEE LPDA + Shorting Stub - OPT
Note that F/B and F/R Ratio MINIMUM is about 20 dB....but on some Frequencies it reaches EXTREMELY High values. So it is extremely unlikely to receive any weak to moderate UHF stations on the BACK of the HD-7694P Antenna.
Although Gain was quite a bit less than the 5-El LPDA+3 Directors+Reflector in HD-7694P, the fol. "comparable size" 8-El LPDA also illustrates the Extremely High F/B and F/R Ratios typical of LPDA Designs: