You cannot take two antennas and make such a conclusion, which is my point. The facts are that UHF digital still uses the same frequency range as the old ones, except that the old UHF channels had some channels abandoned (don't remember just when) for the old analog 800mhz phone service, and those channels pretty much became "cable only."
Frequency is frequency. It matters not what mode the transmission is, and the frequency band has not changed. As I said, there are really poor, and not so poor designs. UHF covers a very broad range of frequencies, so it's not surprising that antennas "vary."
Also, you cannot simply compare element length. Yagi, log periodic, and other parasitic arrays depend on many many factors, not the least of which is element spacing, boom construction, and whether in the case of a yagi, the elements are electrically apart from the boom.
Just because the signal from two antennas you happen to have compared is 20db different is hardly conclusive.
The thing is, an antenna advertised as "digital" may WELL HAVE been optimized better for UHF channels, and I freely admit that the LIKELYHOOD is that most will indeed be on UHF, but again that is an individual antenna to antenna design difference, not some general characteristic that can be pasted on by a "DTV" label.
According to this:
http://www.antennasdirect.com/faqs.html#faq1
currently (prior to June 2009), 91% of broadcasting DTV stations are on UHF. A few cities, such as Chicago and Las Vegas have DTV stations on VHF as well as UHF. While Many DTV stations are now occupying UHF broadcast channels, the plan will allow some broadcasters to move back to their original VHF or UHF TV channels once the transition to DTV is complete. After June of 2009: 74% of the DTV stations will be on UHF (14-51), 24% will be on high VHF (7-13) and less than 2% will be on Low VHF(2-6).
And according to the FCC:
http://www.fcc.gov/guides/antennas-and-digital-television
To receive digital TV signals from all stations, it is important that your antenna be able to receive both VHF channels (channels 2-13) and UHF channels (channels 14-51). Some antennas only provide good reception of VHF or UHF channels, but not both. For example, indoor “rabbit ears” usually need to be augmented with an additional “wire loop” or “bowtie” antenna (see pictures below) in order to pick up signals on UHF channels. Consumers should be aware that even if they use a digital-to-analog converter box, they will still need to use an antenna to receive DTV signals. Many of the antennas currently being sold as “HDTV Antennas,” perform best at receiving UHF signals; some of these models state that they provide reception of signals on channels 7-13 but actually perform less well receiving those channels. If you obtain one of these antennas, be sure it provides good reception of all the VHF channels as well as the UHF channels. The reception capabilities of TV antennas also vary considerably,
So I guess if you "read into" this, you can conclude that currently marketed antennas are being somewhat optimized for UHF. Again, this has nothing to do with the buzzword DTV.
I guess what I'm trying to get across here, is that the word "DTV" does not magically change an antenna. Antennas are still subject to good and bad design and marketing the same as they always have.
