Are there any AM-HD broadcasts going on at night ? ?

[CW]

I would advance that at whatever frequency a carrier-less system operates, they need a reference for accurate decoding.
I suspect it is easier at the very high frequencies digital TV is allocated. If there is enough bandwidth to carry
video signals. it is pretty easy to throw in a few bits for a comparator to use as reference.

I don't know enough about digital TV modes to say with any better than this above guess.

Actually there is a reference signal for 8-VSB television. If memory serves me correctly, you can find a "carrier" signal of sorts approximately 310kHz above the lower boundary of the 6MHz channel segment. I can hear that "dead carrier" on any of my local DTV stations if I just add .310 to the lower boundary of the channel, using either of my scanners that can tune the VHF and UHF bands in AM or NFM mode.

Correct....a reference spike.....you can see it on a spectrum analyzer..its there...just not on ZERO freq of the lower end of the channel...but then analog was not that either...its CARRIER was 1.25 MHz up from the lower end of the channel.

 

[PhilJSmith67]

I think the point here is that you can't eliminate the carrier and/or any reference signals completely. According to iBiquity's specs, even the digital-only IBOC modes on AM and FM both have a carrier/reference signal, although it is greatly reduced in strength compared to today's hybrid signals, and the OFDM symbol carriers are packed very closely, frequency-wise, to the reference signal.

 

[TheRover]

Update for Dallas-Ft.Worth:

Thursday Night, July 31, 2008, after 11pm, I got KLIF 570 AM in HD. Sounded Good.

I also got KRLD 1080 in HD the same night.... Sounded bad. Maybe they were testing it then. After midnight that night, 1080 is not in HD.

570 is still in HD after midnight.

 

[OKCRadioGuy]

"R.F. Burns:
Your argument about complicating remotes is amazing to me. Who other than the smallest broadcaster with the smallest number of listeners uses an over the air signal for return cue? Any legitimate operation today uses ISDN or some other digital link for sporting events. Even smaller stations could use a Comrex Hotline/Matrix/Access, you name it. All of the devices I just mentioned provide for a clean mix minus return cue and if you use a ISDN with AAC LD coding there is no serious delay caused by coding. To program a sttion to serve the relatively small number of people who carry radios to a stadium is in my opinion, rediculous."

For the record I have been engineering high school football games on a local 50,000 watt radio station for over 15 years. We use and will continue to use off-air montoring for all local games, which in our case is ALL games except one every other year. We use analog RF Martis. You know what? It is pretty DAMN reliable. In fact I consistantly watch other broadcasters with their assorted new crap have drop outs here and there and scramble around like chickens with their heads cut off. Guess what? Good old analog junk just keeps plugging away. Go figure. Also, have you considered that ISDN is not only expensive but harder to get installed these days? Even getting POTS drops at every high school stadium is getting expensive because most schools have cut their lines off. That leaves cell service of some sort or IP. I can sort of trust IP streaming if there are no firewall issues, etc. but the cell networks aren't that reliable all the time. I know of at least two broadcasters around here that have the cell capability and only use it when they absoluely have to. You know, some times the old way actually is the better way.

 

[R.F. Burns]

"R.F. Burns:
Your argument about complicating remotes is amazing to me. Who other than the smallest broadcaster with the smallest number of listeners uses an over the air signal for return cue? Any legitimate operation today uses ISDN or some other digital link for sporting events. Even smaller stations could use a Comrex Hotline/Matrix/Access, you name it. All of the devices I just mentioned provide for a clean mix minus return cue and if you use a ISDN with AAC LD coding there is no serious delay caused by coding. To program a sttion to serve the relatively small number of people who carry radios to a stadium is in my opinion, rediculous."

For the record I have been engineering high school football games on a local 50,000 watt radio station for over 15 years. We use and will continue to use off-air montoring for all local games, which in our case is ALL games except one every other year. We use analog RF Martis. You know what? It is pretty DAMN reliable. In fact I consistantly watch other broadcasters with their assorted new crap have drop outs here and there and scramble around like chickens with their heads cut off. Guess what? Good old analog junk just keeps plugging away. Go figure. Also, have you considered that ISDN is not only expensive but harder to get installed these days? Even getting POTS drops at every high school stadium is getting expensive because most schools have cut their lines off. That leaves cell service of some sort or IP. I can sort of trust IP streaming if there are no firewall issues, etc. but the cell networks aren't that reliable all the time. I know of at least two broadcasters around here that have the cell capability and only use it when they absoluely have to. You know, some times the old way actually is the better way.

I can state with certainty that until a few months ago WINS in NYC was using its over the air signal to cue its reporters. That has been changed now that they have switched over to IBOC. I've engineered remotes both large and small for over 35 years and have used everything from over the air signals, land lines, ISDN you name it for return cues. Each situation is different and trying to compare the needs of getting a signal in and out of most cities in this country and Manhattan won't work. Manhattan's skyline is enormous compared with every other city in this country. This isn't a slam against other cities but using RF only paths for cuing in NYC would prove difficult if not impossible and when you're talking about reporters for an all news station any system for two way communications would have to be portable while allowing for the insertion of recorded audio from the device in the field. At my workplace we’ve even used Inmarsat to get a signal from the Morning Side Heights section of Manhattan to midtown, when land based ISDN wasn’t easily available.

 

[Play Freebird]

For the record I have been engineering high school football games on a local 50,000 watt radio station for over 15 years. We use and will continue to use off-air montoring for all local games, which in our case is ALL games except one every other year. We use analog RF Martis. You know what? It is pretty DAMN reliable. In fact I consistantly watch other broadcasters with their assorted new crap have drop outs here and there and scramble around like chickens with their heads cut off. Guess what? Good old analog junk just keeps plugging away.

You make a very good point.

At the Philadelphia FM station where I was CE for twelve years, we had a VHF Marti system which I modified with outboard noise reduction (prototype Radio Systems Dolby S compandors which I bought cheap) and it sounded fine. Audio response started to roll off above 10 kHz but this wasn't really noticeable. At the remote site, I simply plugged an FM tuner into the PA amplifier and the jock's headphone amp; there was no need to run mix-minus or any special feeds. For IFB, we had a choice of SCA or a 450 MHz repeater installed at the transmitter site. All analog with virtually no delay.

The advantages of this system were portability, reliability, and low cost. I could quickly arrange for "ad hoc" remotes in locations where Verizon wouldn't run lines, for instance in Fairmount Park for the Dad Vail Regatta, and on the sidewalk outside Veterans Stadium. Noise reduction took care of the hiss which is often a problem with RPU signals less than 100 microvolts, so it wasn't unusual to make clean shots from 25 to 30 miles out. We used horizontally polarized yagis on both ends (with a bandpass cavity on the receiver) and never had a hint of intermod. Needless to say, this system avoided the hassle and expense of ordering ISDN service from Verizon.

We did use ISDN for the nightclub and concert venue remotes that were scheduled on an long-term basis and set up by interns or part-timers, but on several occasions I had to use the RPU system at some of these sites because the ISDN had failed. Verizon was such a PITA to deal with on disconnect orders. At least half of these weren't entered properly in their system and I would continue to be billed for service that should have been canceled months earlier.

I'm now part-owner of a small market AM station that recently began simulcasting on an FM translator. I doubt that the local carrier could provide ISDN service even if we were willing to pay for it. So to improve audio quality, we recently installed an RPU system and will begin using this wherever possible, instead of our older cellphone-based system.

I realize that New York City is a different kind of environment -- but in most other markets, analog RPU continues to do a fine job... and it's so much less expensive than the digital alternatives!