Savage said:
rbruce, not to speak for everyone else, but I wasn't (and I don't think others were) taking liberties with your initial post. We were all just having a little fun. Hope you weren't offended. Your contributions here are indeed rational and well-reasoned.
Oh no - I wasn't offended by anybody's post. I took it in the spirit. I merely wanted to point out that the measurement data is what it is - and it does not support the industry's claim that a 10 dB power increase is warranted.
Another aspect of coverage is that many listeners in smaller metro areas (geographically) are too near airports. Aircraft reflection is immediate death to HD lock as listeners in the DFW metroplex have noted, some no more than 10 miles from the full class C sticks. Van Alstyne is not on the approach path to DFW airport, and 70 mile reception was easy. I suspect that may be a hidden coverage problem that was not thought through when the system was proposed. No 10 dB power increase will help - the signal variations are several decades, not one decade.
I have never been a proponent of AM HD, the coverage is lousy, robustness not there, and sound quality is poor, nowhere near FM quality. I get listener fatigue in minutes even when I am fully locked on a strong station, the artifacts are annoying. I have contrasted coverage tests on C-Quam vs. HD, there is no comparison. 290 miles in perfect stereo for C-Quam on a 5 kW regional, vs. 20 or 30 miles once the same station converted to HD. Since the DFW metroplex is 80 miles wide and 60 miles NS in places, it stands to reason C-Quam is the better choice to cover it. There have been documented cases of 160 mile AM HD reception from 50 kW stations such as WBAP (which has turned off HD for quite a while now), and some documented nighttime cases. But the AM system is obviously not going to fly, and the sidebands are horrific. One of my projects will be to document 1000 mile sideband hash in the daytime if I get the chance to go out west this summer. I know I wasn't imagining it, I just need to do it again with an ordinary car radio and put the video on Youtube or something. Unless somebody else can beat me to it --- It gets really obvious which station is the offending station when there aren't that many on the air around the country, and sideband pairs from places like Chicago start showing up in the right places on the dial in remote places in New Mexico.
As far as FM HD, I know KKBQ has HD, and I measure my distance from it at about 280 miles. If a local AM talker hadn't just started jamming the frequency with their garbage, it was only a matter of time until I got an HD lock on KKBQ, the analog signal was so good. I may be moving, perhaps I can get a better selection of medium to deep fringe targets from my new location - wherever I end up. Suffice it to say I've seen documented reports of 100 to 120 regular HD reception from other parts of the country, on stations that are not full class C. How far does HD go reliably on a full class C with a good antenna? I don't know yet. I would guess 150 or so, perhaps 200. Definitely not as far as analog that can go 300 for a class C with a good antenna. A lot depends on first adjacents - which tend to get prevalent that far out. My guess is that the HD folks don't care at all out in the fringes like that, but 10 dB sideband power increase might help in the deep fringes 200 to 300 miles out. That is extreme DX, and there probably isn't but a handful of people around the country that are in the position of doing it on a regular basis. Dropouts are inevitable at those distances even in analog.
