93.3 KLIF-FM Not Broadcasting in HD

[texasstooge]

I have some good news: KLIF-FM 93.3's HD signals are back online. My guess is that they had to get a newer HD antenna.

 

[TheRover]

I have some good news: KLIF-FM 93.3's HD signals are back online. My guess is that they had to get a newer HD antenna.

That's nice. I don't listen to 570 as much, since they dropped Michael Savage.

 

[rbrucecarter5]

93.3 is not broadcasting in HD. I miss the HD-2 signal, the simulcast of 570.

Now I go from the FM band over to the AM band to listen.

Not as convenient for me.

Given 93.3's weak signal - shutting off HD is a smart move. That should definitely increase coverage of the analog signal.

 

[Jay Walker]

Given 93.3's weak signal - shutting off HD is a smart move. That should definitely increase coverage of the analog signal.

Allow me to clear up a misconception please.

HD does not effect the analog coverage of FM. With or without the HD carrier(s)/sidebands the 60dbu analog FM coverage is the same. In my experience with multiple HD/FM systems I have never experienced any reduction OR increase in analog FM coverage with OR without the HD carrier(s) on line. That includes HD1/2 and 3. As a point of, fact when the HD carrier(s) are active on a high level/low level combined system the on channel TPO (total power out) increases by a minimum of -20db referenced below the analog FM carrier. If the HD carrier(s) are running at the recently allowed level of -10db below analog FM the on channel TPO will increase by the same ratio i.e. -10db.

Yes, there is an increase in the on channel total power output when the HD carrier(s) are active, but the digital carrier does not carry the same type of modulation (Quadrature versus Frequecy modulation) so the listener will not percieve any change in coverage on the analog FM signal nor is there any increase or decrease in the relitive field strength.

I have verified this with RF field strength readings on numerous stations...

Jay Walker

 

[rbrucecarter5]

Allow me to clear up a misconception please.

HD does not effect the analog coverage of FM.
I have verified this with RF field strength readings on numerous stations...

Jay Walker

Yeah - that is the party line, for sure. I'm just a plain old DX'er, who drives the route a lot between Houston and Dallas, and noticed the change in analog coverage of both city's stations pre and post HD conversion. In every single case, analog coverage is drastically reduced post HD. The most dramatic was on Houston's 107.5. I know it is HD, because it not only converted to HD, it took down HD for a time, then HD came back. Pre-HD, it was solid as a rock to Madisonville, with good reception to Centerville. Post HD, it was barely receivable in Huntsville, and degraded badly over Conroe. That is a loss of of over 60 miles of analog coverage. That was repeatable over many trips, different times of the day, different times of the year. HD gone - coverage was immediately back, HD back on - coverage lost. Other stations are losing 30 to 40 miles of coverage. I know the scientific method. I use it every day. It applies here, the results are demonstrable and repeatable under all conditions except maybe strong skip which by its nature is unpredictable.

I think the confusion comes when broadcast engineers look at the coverage with RF field strength meters - instead of looking at a reception scenario as a SYSTEM, with the consumer's receiver a portion of that system. What I think is happening is that the extra RF energy in the side bands is confusing the AGC circuitry in tuners, causing it to lower the receiver sensitivity and/or interpreting the sideband signals as noise. This is going to be very hard to overcome with any power increase, because the tuner will automatically respond by further lowering the sensitivity to accommodate the increased signal level (of noise). The result may be even less analog coverage, not more digital coverage.

I've noticed this across the board with many radios in many cars, ranging from top of the line Pioneer Supertuner 3D in my car to stock radios in rental cars. I definitely repeated the results on frequent trips to LA, pre and post HD. The problem is HD, and it does affect analog coverage dramatically.

In case somebody brings up the tired old argument about "people in Centerville don't care about Dallas / Houston" or "Dallas / Houston don't care about Centerville", keep in mind that analog coverage directly scales into buildings. At a time when stations are whining about penetration into buildings, the last thing they need to do is convert to HD, which decreases analog coverage repeatably.

 

[Megapsycle]

texasstooge... I have some good news: KLIF-FM 93.3's HD signals are back online.

Thanks I'll have to re-connect my Sangean HD tuner and try it again. I pulled it out of service and put in my old Scott LT-112B tuner I built as a kit in 1969. The Scott has superior analog audio compared to the Sangean which only sounds minimally better than AM on FM analog; the non-HD tuner built in to my Pioneer AV receiver is noisier on the HD stations for that matter.

I've noticed with most tuners I've tried the HD FM stations will have a slight underlying background hash noise. WRR FM is good to demonstrate this. My old Scott tuner does not have the background hash noise from HD. I wonder if that is what is reducing your range rbrucecarter5?

 

[rbrucecarter5]

texasstooge... I have some good news: KLIF-FM 93.3's HD signals are back online.

Thanks I'll have to re-connect my Sangean HD tuner and try it again. I pulled it out of service and put in my old Scott LT-112B tuner I built as a kit in 1969. The Scott has superior analog audio compared to the Sangean which only sounds minimally better than AM on FM analog; the non-HD tuner built in to my Pioneer AV receiver is noisier on the HD stations for that matter.

I've noticed with most tuners I've tried the HD FM stations will have a slight underlying background hash noise. WRR FM is good to demonstrate this. My old Scott tuner does not have the background hash noise from HD. I wonder if that is what is reducing your range rbrucecarter5?

HD self noise is well documented, and gets much worse with the 10dB power increase. This self noise would be more noticeable on formats like classical that have quiet passages.

That was my point - the tuner has no way of differentiating whether a signal is noise, or man made intentional noise (HD). It will open up or close down AGC gain in response to the signal levels it encounters. Add HD sidebands into the mix, and they are part of the AGC gain feedback path. So the analog section of the signal may show no attenuation in the analog portion of the waveform. It wouldn't even show attenuation if the measurement bandwidth was expanded to the point that all of the station spectrum, including HD sidebands are encompassed. But an RF spectrum analyzer has no AGC function. An FM tuner - be it car, home, or portable does. And even the best AGC circuits just "sample" everything passed by the IF, noise, adjacent channels, HD sidebands, analog - all of it. The only thing a tuner manufacturer can do to overcome this is to implement adaptive IF, like they have in Pioneer Supertuner 3D and the Sony XFHD1, probably a few other models. By narrowing down the IF, the AGC will not be confused by sideband signals, and SHOULD restore analog sensitivity. I've only tested with fixed bandwidth tuners, there is a chance adaptive IF would focus on weak analog signals, open up the gain, and the radio would be as sensitive as before the HD switch. Assuming there is not some funny cancellation going on due to HD. FM modulation is a pretty complex equation even without HD, I don't think I've seen any derivation of the signal including HD. Anywhere. So the potential for cancellation is definitely there. It is a problem even with analog subchannels starting with the FM stereo system itself. Add in RDS, SCA, teletexting, HD, and who knows what other garbage, and you got quite a recipe for interference and cancellations. If I were a station owner, I'd can everything but analog stereo. And if I were an FM talk / sports, I'd even can the stereo. Some FM stations do just that, and claim (or actually measure) increased coverage.

HD - bad idea, inadequately engineering, inadequately tested, high pressure marketed to station owners - who greedily saw advertising dollars on HD-2 channels. Only problem was, analog FM wasn't "broken" in the eyes of the consumer the way NTSC video was. One look at an HD screen and the consumer was convinced. One listen to an HD radio sounded no different than an analog radio. No compelling reason to switch. If HD is causing reduced coverage in the fringes, you can bet it is inside of buildings downtown. So any station owner who is counting on analog coverage in the fringes - like Houston's KGLK 107.5 needing to cover rich suburbs in the Woodlands and Conroe - had better think twice before going down that route. KGLK eventually had to program KHPT 106.9 in Conroe with a simulcast to restore coverage they lost because of HD. It would have been far cheaper, I suspect, to simply dump HD and restore the excellent coverage they used to have all the way to Madisonville. The Woodlands and Conroe were a piece of cake with their analog only signal, even reaching down into canyons around Lake Conroe with an excellent signal on 107.5, which vanished almost completely after the HD conversion.

Of course, saying all that is heresy, and I expect the HD advocates to jump all over me. They cannot let facts contradict the party line.

 

[Jay Walker]

rbrucecarter5
Thanks for your insight and field observations. I'll give it a try and see if I can get the same results.
At my listening point on the Collin/Grayson county line I am in the 50-60db contour for the full "C" stations at Cedar Hill. From my spot at 650ft AMSL I have not experienced any signal degradation on my system with or without HD. I use a Carver TX-2 analog tuner with an Omni-directional crossed dipole array horizontally polarized at 25ft. This is my "house standard" for comparative listening. The field readings I referenced were taken with the Potomac Instruments FIM-71 Field Strength Meter we've used for years to do plots.

I found your thought about the possible AGC issue caused by the sidebands interesting, and I'll explore that direction to see what I can see or in this case hear.

Thanks again and I'll check it out.

Jay Walker

 

[TheRover]

Re: 93.3 KLIF - FM Not Broadcasting in HD

KLIF is broadcasting on HD for their main channel, but there is now no HD-2 signal.