Strubel Responds to Tom Ray

[Savage]

Yeah - I'm not sure about what the cause/effect was with better reception of our station in the fringes in 10 kHz as opposed to 6 kHz, but I have theories.

It could be that the wider signal masked adjacent-channel local noise from electrical equipment, distant stations, etc. better. Or it may be that psychoacoustically, a distant AM signal showing familiar weak-signal characteristics (fading, increased noise floor) sounds more pleasing if it has highs and lows. There could be a masking effect. That's what I'm thinking, but of course can't prove it.

I do know that from practical experience, many AM car radios are nowhere near as narrowband as some HD pundits claim (and conversely, some AM car radios are truly horrible, like the loaner Honda Civic I drove last week which made every AM station sound like a phono oscillator from the 1950s.) The examples I cited were my (former) 2005 Jeep and Pontiac which supposedly had 4 kHz response. Guess the radios weren't shown the lab charts, because anyone could tell the difference between 6 khz and 10 kHz - without any professional training.

Maybe these kinds of radios are down several dB at 4 kHz, but the response sure ain't GONE.
I now have a Jeep Patriot with a pretty good AM section. And IBOC stations sound like doo-doo on it. If the bandpass is literally only 4 kHz, IBOC stations should sound just like 10 kHz all-analog stations. But they don't....not even comparable.

 

[local oscillator]

In a nutshell, I am very much anti-AM HD, okay with FM HD for the most part and mad that the FCC doesn't take HD interference complaints on both bands more seriously.

Zach, I'm glad you see the problems with AM HD, but I'd like to know why you're OK with FM HD which is every bit as much a disaster. It's bad enough now, but if ever the stations between the large market stations (which are usually 4 channels apart) turn on HD and/or stations start increasing HD power to -14 dBc or -10 dBc in great numbers -- watch out!!! It's a lot like paying the RIAA streaming royalties; you have to look at the end game.

 

[tomservo]

In a nutshell, I am very much anti-AM HD, okay with FM HD for the most part and mad that the FCC doesn't take HD interference complaints on both bands more seriously.

Zach, I'm glad you see the problems with AM HD, but I'd like to know why you're OK with FM HD which is every bit as much a disaster. It's bad enough now, but if ever the stations between the large market stations (which are usually 4 channels apart) turn on HD and/or stations start increasing HD power to -14 dBc or -10 dBc in great numbers -- watch out!!! It's a lot like paying the RIAA streaming royalties; you have to look at the end game.

Well, from a consumer standpoint, I haven't really heard the problems that some people on here say are a deal killer. BUT — and this is a big caveat — I live in the south where urban areas are far apart and generally have a slew of well-spaced class C's.

I've never been up in the regions where stations are close spaced, like between DC and Ballermore or Chicago and Milwaukee to listen to the effects of FM HD.

But down here, none of the bad things that were said to happen have really happened, that I can tell. There's only two HD stations really close enough at my home, both part of our state-wide public radio network. I'm 37 miles from one 100 kW stick and 50 miles from the second. Unless this computer monitor is on, I get the first with little effort and the second with a little fiddling about. (Note: with this computer monitor on, ALL analog signals are severely compromised anywhere in the area, so the lack of HD is not a unique issue here.)

But the greater worry of the anti-HD crowd is first adjacents. The fact is I am losing no signals because, despite the great distance between me and the stations, there are no viable first adjacents to either signal to begin with. And during this summer's good DX season, the HD sidebands did not preclude me from logging more stations on those frequencies, even though the radio was still decoding the HD signals.

Maybe there's more cause for worry up in the New England corridor, but for the rest of us the adjacent sidebands are simply not an issue. If there's been any loss of analog coverage it's obviously not been enough of an issue to generate significant complaints (except for me, I'm convinced that one of the aforementioned public stations' signal has suffered significantly, but I can't tell if that's due to the new wideband antenna for HD, or the lowering of the FM antenna after the DTV switchover, since it's on the ETV tower.)

Yes, I've had some reception issues with my Insignia portable radio, but it's been concluded that my model is particularly defective, in that some days it's solid and some days the front end falls apart when adjacent strong signals overwhelm it. But as for HD, it has worked for me so far pretty much anywhere within the 60 dBu contour that one sees on the FCC site. I've checked this in Jackson, Miss; Memphis; Little Rock; Saint Louis; Albuquerque; Oklahoma City; Las Vegas and Los Angeles. Really only Albuquerque's few HD stations failed to perform up to snuff in the urban environment, but that may be due to factors beyond my knowledge, like HD antenna placement, etc.

Saint Louis in particular was a real "wow" market, with me easily getting 50 miles out without a single dropout on HD2 channels and several real good sounding feeds. But I realize it may be the exception rather than the rule. I regret not being able to bring my HD radio on a trip last year to Chicago, that would have been a real good test bed.

Before I got an HD portable, I did get plenty of analog-listening experience in, around the Birmingham market back when they were fairly early to the HD party. In town, with many Class C FMs running HD looking down upon me, I did not notice any detrimental effects to the dial. To wit, the closest stations on the dial might be a C on 93.7 and a C on 94.5, both running HD, but neither causing any undue new interference to an out-of-market C on 94.1 that is analog only, with a stick nearly 70 miles out of town. And 70 miles out of town (in the 94.1 stick area) the other two stations seem no more compromised in the analog realm, even though the HD has long bit the dust.

Even though I'm okay with FM HD, it is by no means something I'd encourage a class A in any town or market to adopt, or anything I'd ever want to see on a translator, for example. At its best, though, it really is pretty seamless and the benefits of a well-processed digital stream really are worthwhile from a listening standpoint. But in all the above listed cities, I can count the number of in-sync and well processed HD stations on six fingers. But that is a problem for engineering to solve ("general" engineering, not necessarily stations engineers) and will improve over time.

 

[local oscillator]

Zach, thanks for the thoughtful response. I can certainly understand that individual experiences can vary widely. With the HD "landscape" where you live and where you've traveled, the effects of the interference HD causes are probably not yet in evidence. Most of it is now showing up in the northeastern quadrant of the country plus California. If more and more stations go HD and/or increase digital power (please, no!) the situation will be terrible in the northeast and California and will start to show up elsewhere. You are absolutely correct that the current concern is HD interference to first-adjacent analog reception. There are several examples already that would make your jaw drop. I also agree with you that HD isn't something a Class A should ever do. Many, if not most, couldn't even if they wanted to. So many Class A's are second-adjacent on both sides to Class B/C's, so both HD sidebands would be clobbered by the Class B/C sidebands anyway. It seems iBiquity's only concern was for the big-market, group-owned stations that tend to be Class B or C and spaced every four channels in their respective markets. The time-tested FM allocation scheme which has worked so well for decades only does so when all stations are assumed to occupy one channel, not three. The problems with HD on AM are so evident, no reasonable person could deny them. The problems with HD on FM are of the stealthy, incremental variety; before many realize how bad the disease is, it will be terminal.