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Trashed AM Frequency of the week: 700

Back to 1570 for a moment: in the 60s there were daytime-only 1570s in Texas and far SW Oklahoma which would have been relatively close to XERF. But in the Mountain time zone states, there were but two 1570s, one in Loveland CO at 250 watts daytime only, and the other in Salt Lake City, which was a 500 watt daytimer. Today, it's just the 1570 in Loveland; the 1570 in Salt Lake either found a better freq. or left the air. The treaties with Mexico made 1570 a tough choice in the SW US to be sure, but in the sparsely settled states of the west, there was usually a graveyarder available or at least a Class III regional omni daytimer lower on the dial. As a result, in Colorado 1570 usually presents XERF mostly by itself at night.

On other trashed clears, 880 KRVN at Lexington NE always has something underneath it at night in Colorado...I'm going to have to listen to see just who that might be.
 
joebtsflk1 said:
Back to 1570 for a moment: in the 60s there were daytime-only 1570s in Texas and far SW Oklahoma which would have been relatively close to XERF. But in the Mountain time zone states, there were but two 1570s, one in Loveland CO at 250 watts daytime only, and the other in Salt Lake City, which was a 500 watt daytimer. Today, it's just the 1570 in Loveland; the 1570 in Salt Lake either found a better freq. or left the air. The treaties with Mexico made 1570 a tough choice in the SW US to be sure, but in the sparsely settled states of the west, there was usually a graveyarder available or at least a Class III regional omni daytimer lower on the dial. As a result, in Colorado 1570 usually presents XERF mostly by itself at night.

On other trashed clears, 880 KRVN at Lexington NE always has something underneath it at night in Colorado...I'm going to have to listen to see just who that might be.
Click to expand...

Your 880 might be WCBS. It used to be fairly clear in West Texas at night prior to KRVN. If they aren't running the power vampire HD, it is plausible that the would make it into Colorado.
 
880 here is WCBS but I can hear the Cubanos on there in the early evening as well as over 890 WLS. But the Cubanos power down late at night (no ratings?) and both stations are then in the clear.
 
kf4rca said:
880 here is WCBS but I can hear the Cubanos on there in the early evening as well as over 890 WLS. But the Cubanos power down late at night (no ratings?) and both stations are then in the clear.
Click to expand...

The Cubans stations do not power down at night; I think you are confusing sunset skip conditions with later night conditions. The whole idea of lower night power is virtually unknown in Latin America except in Mexico.

There are no ratings in Cuba as far as I know, as all radio is state operated.
 
Power Vampire?

rbrucecarter5 said:
...Your 880 might be WCBS. ... If they aren't running the power vampire HD, it is plausible that the(y) would make it into Colorado.
Click to expand...
IIRC, the radiated power of the analog AM carrier and its upper/lower analog AM sidebands is the same whether that station radiates HD signals, or not. The power in the HD r-f waveforms is added to the normal AM signal by transmitters designed to do so, without affecting the power in the analog carrier and its analog AM sidebands.

Therefore adding HD to a conventional analog AM transmit signal would not change the field intensities that analog signal produces at receivers (other things equal).
 
Just Kidding About Ratings

There's no listeners late at night. And gov't radio is boring.
Radio Progresso (890) operates with 250KW. So it can probably be heard thru out North America, even after midnight.
But both 880 and 890 are remarkably clear after midnight at my location.
So I think they power down or sign off. Radio Progresso features what I would say are live nightclub broadcasts.
I suppose you are aware they never did get the nuclear plant the Russians were building for them going so electricity (fossil fueled powered) is not cheap for them.
 
kf4rca said:
There's no listeners late at night. And gov't radio is boring.
Click to expand...

There is plenty of night radio listening in Cuba. First, TV is less pervasive a medium, and second, the quality of the TV offerings tends to be limited and poor, with lots of state propaganda.

Radio Progresso (890) operates with 250KW. So it can probably be heard thru out North America, even after midnight.
Click to expand...

Most of the Cuban frequency / power lists are inaccurate. Cuba does not report to any international frequency allocation entity, and the use of transmitters and sites can vary quite often.

But both 880 and 890 are remarkably clear after midnight at my location.
So I think they power down or sign off. Radio Progresso features what I would say are live nightclub broadcasts.
I suppose you are aware they never did get the nuclear plant the Russians were building for them going so electricity (fossil fueled powered) is not cheap for them.
Click to expand...

Progreso has live broadcasts of orchestras from their own studio / auditorium. I believe they have done that for about 60 years!

Cuba has a sweetheart deal with Venezuela and gets fuel for nearly nothing. Thank Horrible Hugo for that.
 
I'd be very willing to bet the entire farm that the Cuba 890 isn't anywhere near 250KW. Based on my own experiences (day and night) in and around Florida, I'd be surprised if they're any more than 30KW.

DavidEduardo said:


Progreso has live broadcasts of orchestras from their own studio / auditorium. I believe they have done that for about 60 years!
Click to expand...

I've heard some of these. Very entertaining! In front of a live audience, IIRC,
 
Interesting to note that about half the time I tune to 700 at night here, WLW is there.

It's mostly weak and barely audible but still there.

Same goes for WWL on 870.
 
Was listening to WLW late last night driving around Columbus, maybe an hour after this report of KHSE being heard, and there was nothing else on the channel. We're farther from Texas, of course, and probably a little closer to the WLW tower. Will have to listen again when I get the chance.
 
rfry said:
IIRC, the radiated power of the analog AM carrier and its upper/lower analog AM sidebands is the same whether that station radiates HD signals, or not. The power in the HD r-f waveforms is added to the normal AM signal by transmitters designed to do so, without affecting the power in the analog carrier and its analog AM sidebands.

Therefore adding HD to a conventional analog AM transmit signal would not change the field intensities that analog signal produces at receivers (other things equal).
Click to expand...

So I have been told. Not what I have observed. I think people confuse field strength meters with radio receivers that have AGC. If the HD sidebands confuse the AGC circuitry, the radio will ramp down its gain and be less sensitive. I've noted this coverage decrease (and therefore less building penetration) on every single AM station that runs HD. And a fair number of AM stations have noticed it too, and dumped HD. Most notably WBAP and WOAI here in Texas. WBAP has always prided itself on its big footprint, service to rural areas, and service to truckers. Their coverage came back the moment they switched off HD. Same with WOAI - who I assume is going after the expanding Austin market. If KLVI bills itself as a Houston station, WOAI can surely bill itself as a San Antonio / Austin station. Their coverage came right back, too, the moment they turned off HD. Some of the 50 kW clears that shut it off come in again - after years of absence or weak signal. There is definitely some mechanism at work here that has not been well understood. But the solution is simple - shut off HD. It really has no advantages for AM anyway, unless you consider stereo musical beds on a talk station something to be desired.
 
WLW in the clear here. And, lately 890 is also. BUT, 880 WCBS gets trashed by Radio Progresso about 11PM or so. 880 Cuba is CMAB out of Pina del Rio running 30KW or so.
 
rbrucecarter5 said:
So I have been told. Not what I have observed. I think people confuse field strength meters with radio receivers that have AGC. If the HD sidebands confuse the AGC circuitry, the radio will ramp down its gain and be less sensitive. I've noted this coverage decrease (and therefore less building penetration) on every single AM station that runs HD. And a fair number of AM stations have noticed it too, and dumped HD. Most notably WBAP and WOAI here in Texas. WBAP has always prided itself on its big footprint, service to rural areas, and service to truckers. Their coverage came back the moment they switched off HD. Same with WOAI - who I assume is going after the expanding Austin market. If KLVI bills itself as a Houston station, WOAI can surely bill itself as a San Antonio / Austin station. Their coverage came right back, too, the moment they turned off HD. Some of the 50 kW clears that shut it off come in again - after years of absence or weak signal. There is definitely some mechanism at work here that has not been well understood. But the solution is simple - shut off HD. It really has no advantages for AM anyway, unless you consider stereo musical beds on a talk station something to be desired.
Click to expand...

I don't particularly want to advance the back-and-forth that these posts seem to spur, but I have seen (more accurately, heard) it too. I saw it with WBAP when I lived in the Houston area. Considering this is a thread focusing on 700, this phenomenon was very noticeable on WLW when it was IBOC, and I heard it with the Chicago 50Ks in Indiana and here in Ohio both day and night when all or some of them were IBOC. The loss of coverage is noticeable, as is the improved coverage and much louder, crisper audio without IBOC.
WLW's signal was noticeably worse here in Columbus when it was IBOC, and it has been much better in the years since it turned the crap off. Same with our local WTVN when it was in HD and I tried to listen from other parts of the state.
 
schmave said:
I don't particularly want to advance the back-and-forth that these posts seem to spur,...
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Me either, but I am interested in considering all viewpoints on the topic. That lead me to ask the following question to a respected and well-known research & manufacturing engineer in the broadcast industry:

Q: Hello, XXX - Just wondering if you could refer me to any published works/experience/thought about how using HD on an AM station might cause an analog AM receiver AGC to reduce the gain of the RF/IF circuits, and produce a noisier output than for the conventional DSB AM signal alone. Thanks for whatever you can think of...

A: Hi Dick. I don't think I have ever seen anything about that kind of effect. Most of the interference energy produced by AM HD is in the adjacent channel sidebands, in the 10 to 15 kHz range. Given the typical two-pole AM IF filter with a 4 kHz bandwidth (2 kHz audio), those sidebands will be attenuated a minimum of 28 dB. So the potential effect there will be just a fraction of a dB.

The HD sidebands that will be in-band will be the "tertiary" sidebands. Those are in quadrature with the carrier and will only affect the envelope at high negative modulation levels, such as -90%. The tertiary sidebands will tend to "fill in" the negative envelope peaks. So when you LPF the envelope to get an AGC signal, the AGC signal will be slightly higher than it would be without the HD. Again my guess would be a fraction of a dB, not too much.

In my experience the tertiary sidebands themselves are probably the worst form of self-interference. A few years ago (May 28, 2010), before KFBK-AM turned off IBOC, I made a recording of the effect. To me it sounded like somebody was running a washing machine in the background. The effect was greater at night with a little bit of selective fading. Fading rotates the sidebands so that they develop an in-phase component which becomes directly audible on an envelope (or synchronous) detector.
//
 
rbrucecarter5 said:
And a fair number of AM stations have noticed it too, and dumped HD.
Click to expand...

AM HD is on the decline because it has no benefits to the station, and requires reducing the audio bandwidth of the analog signal.

WBAP has always prided itself on its big footprint, service to rural areas, and service to truckers.
Click to expand...

Perhaps in the past. The station does not sell anything but the Dallas/Ft Worth MSA ratings. Getting shares in Waco, Killeen, Tyler, Wichita Falls or Abilene don't make them additional revenue.

Same with WOAI - who I assume is going after the expanding Austin market.
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Not. WOAI serves the Austin MSA, and gets, on average, less than half a share of listening... good for a 30th overall rank... in Austin. They are not going after anything but San Antonio.

So the real issue should be confined to whether HD is of local benefit to AM stations in their local market. That decision will, then, be based on whether the improved quality of AM HD (debatable) is of any listener benefit (given the paucacity of receivers) or whether the full 10 kHz bandwidth analog signal is the better choice.

You are way to worried about out-of-market coverage. Stations just can't make any additional money from other towns and areas outside the market they are home to. Outside of market coverage has not been a significant sales factor for about half a century, save for a few rural farm stations like KRVN or WNAX.
 
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