UHF antennas like the bowtie units work find with UHF, however, unless you are fairly close or have great line-of sight, they won't help with the high-band VHF.
A little primer:
TV channels used to be:
Low-band VHF: 54 and 88 MHz, containing channels 2 - 6
FM Radio
High-band VHF:174 and 216 MHz, containing channels 7 - 13
UHF 14-69
During the pilot as TV stations started broadcasting HD, in the Portland area they were all in the UHF band, so I started down this road with this:

which was fine for all HD broadcasts before the big switch-over in early 2009. However, at the switchover, three of the Portland stations decided to use the upper VHF bands (8, 10, 12), and guess what? I was unable to receive those stations.
I subsequently purchased a high-band VHF/UHF antenna, and put it on a 35' pole with a rotator and mast-type amplifier.
(new mast, old antenna)

This image shows the old antenna, where the new one is a horizontal Winegard like this:

Using
antennaweb.org, you can define your location and antenna height (below or above 30'); a map displays your location and the transmitting towers available to you in your area.
Distance, trees and hills get in the way as does bad weather, so we struggle with channel 2 which is on UHF 43. Such as life for a cord-cutter in a rural setting.
Here's a list of my stations; I show this because the list contains both the HD channel AND the VHF/UHF channel.
Stations Antenna
KGW-DT 8.1 NBC
RF Channel: 8
31 miles at 41° Blue
KODT-LP 14 A1
RF Channel: 14
17 miles at 212° Blue
KOPB-DT 10.1 PBS
RF Channel: 10
31 miles at 41° Blue
KPTV-DT 12.1 FOX
RF Channel: 12
31 miles at 41° Blue
KATU-DT 2.1 ABC
RF Channel: 43
31 miles at 42° Violet
KOAC-DT 7.1 PBS
RF Channel: 7
38 miles at 188° Violet
KOIN-DT 6.1 CBS
RF Channel: 40
31 miles at 42° Violet
KPDX-DT 49.1 MNT
RF Channel: 30
31 miles at 41° Violet
KPXG-DT 22.1 ION
RF Channel: 22
31 miles at 41° Violet
KRCW-DT 32.1 CW
RF Channel: 33
31 miles at 42° Violet
KRCW-LD 32.1 CW
RF Channel: 5
31 miles at 42° Violet