A clear frequency with no co-channel interference! Unfortunately this is becoming a very rare situation, with all the new stations and power increases being granted. Are there any stations left that have a completely clear frequency in some directions, at least in the daytime, such that their coverage is only limited by atmospheric noise?
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What every AM station wants...
- Thread starter audioguy
- Start date
I would also add no off-channel interference, too! I want to be able to listen to a station that's right at the atmospheric noise level (so that I couldn't copy speech at all, not even determine gender or language, and could only copy music if I heard a few notes in the loudest phrase in the song and know the song as well as whoever wrote it), while I'm close enough to an adjacent strong AM station so that it feels like it's a summer midday in the southwest USA desert even though I'm actually in the middle of a snowdrift. (What field intensity might cause that effect?)
I used to think that was the way it was legally SUPPOSED to be! For example, when you're between stations in the daytime there should be absolutely NOTHING but noise. This would assume you're using fairly decent equipment, like what follows.
The receiver's sensitivity would be such that, with *NO* antenna, it gets clear reception (like a recording studio's master) on a station that the CCRadio2, Superradio, PR-D5, ICF-2010, etc (or whatever is the most sensitive (stock) radio ever made) can't detect at all, even with SSB/CW. (My Tecsun PL-398mp, when I disconnect the internal ferrite, gets absolutely *NO* trace of 50kW 1170 KCBQ in the daytime 9.3 miles away. This radio should be, I'm guessing, at least 120dB more sensitive NOT counting the antenna.)
The antenna gain in dB would be equivalent to reconnecting the internal ferrite on my PL-398mp and inductively coupling to a Select-A-Tenna and utility groundwire. (When doing so, KCBQ's 2nd harmonic overloads severely, indicating 98 dBu.)
So what would the spacing / overlap of stations be, in mV/m (or uV/m), if that was the case? And does any radio+antenna setup exist that is that sensitive?
Also how many stations could be left on the air, if they were supposed to protect each other from not-so-closely-adjacent-channel interference day and night? I'm thinking along the lines of crystal sets that are very wide, like a -6dB BW of ±1 MHz, and a -10dB stop band at ±2 MHz or so, combined with a sensitivity like what's described above.
Going the other direction, what would it sound like if all the TIS stations on 1610 were allowed to erect multi-element antennas (like the highest-ERP-relative-to-TPO FM or TV arrays), with each element being 5/8 wave to send out that high-angle lobe, and feed each element with its own dedicated 2 megawatt transmitter (the highest power I understand is currently being made)?
Now, though, even in the daytime, I know of cases with some significant co-channel interference.
http://www.mediafire.com/?fuy0xipapguub7a
That is 1390 kHz at Pacific Beach, CA, on the Sony SRF-59, hearing XEKT and KLTX simultaneously.
Does anyone know of places where the daytime co-channel interference is worse? (Just using a more sensitive radio+antenna in the same situation doesn't count.)
I used to think that was the way it was legally SUPPOSED to be! For example, when you're between stations in the daytime there should be absolutely NOTHING but noise. This would assume you're using fairly decent equipment, like what follows.
The receiver's sensitivity would be such that, with *NO* antenna, it gets clear reception (like a recording studio's master) on a station that the CCRadio2, Superradio, PR-D5, ICF-2010, etc (or whatever is the most sensitive (stock) radio ever made) can't detect at all, even with SSB/CW. (My Tecsun PL-398mp, when I disconnect the internal ferrite, gets absolutely *NO* trace of 50kW 1170 KCBQ in the daytime 9.3 miles away. This radio should be, I'm guessing, at least 120dB more sensitive NOT counting the antenna.)
The antenna gain in dB would be equivalent to reconnecting the internal ferrite on my PL-398mp and inductively coupling to a Select-A-Tenna and utility groundwire. (When doing so, KCBQ's 2nd harmonic overloads severely, indicating 98 dBu.)
So what would the spacing / overlap of stations be, in mV/m (or uV/m), if that was the case? And does any radio+antenna setup exist that is that sensitive?
Also how many stations could be left on the air, if they were supposed to protect each other from not-so-closely-adjacent-channel interference day and night? I'm thinking along the lines of crystal sets that are very wide, like a -6dB BW of ±1 MHz, and a -10dB stop band at ±2 MHz or so, combined with a sensitivity like what's described above.
Going the other direction, what would it sound like if all the TIS stations on 1610 were allowed to erect multi-element antennas (like the highest-ERP-relative-to-TPO FM or TV arrays), with each element being 5/8 wave to send out that high-angle lobe, and feed each element with its own dedicated 2 megawatt transmitter (the highest power I understand is currently being made)?
Now, though, even in the daytime, I know of cases with some significant co-channel interference.
http://www.mediafire.com/?fuy0xipapguub7a
That is 1390 kHz at Pacific Beach, CA, on the Sony SRF-59, hearing XEKT and KLTX simultaneously.
Does anyone know of places where the daytime co-channel interference is worse? (Just using a more sensitive radio+antenna in the same situation doesn't count.)
You know, pianoplayer, this thread started out with a legitimately interesting question with real-world relevance. There are plenty of interesting questions to be asked and answered about transmission and propagation as they affect real stations and real listeners.
And it seems like every time those questions start to be asked here, you show up and expend a lot of your energy writing long theoretical questions that sail right past real-world relevance off into fantasy land. The general answer to so many of your posts is: "No." No, there's no amount of power or antenna configuration that could make a MW signal usable halfway around the earth by a crystal radio locked inside a Faraday cage inside a salt mine. No, there's no way any receiver can produce armchair audio on a 1-watt station 1000 miles away that's co-channel to the 50 kW station next to which you've positioned your pocket receiver. Just...no. (And I think you know that, too, from the smiley faces that you've been putting at the end of some of these.)
You're a smart guy. That much is easy to tell from your posts. It should be obvious by now that among those of us who are still here on what's left of these boards, you're not getting much (if any) response anymore to these "way out there" scenarios. So maybe you can satisfy my curiosity, at least: why do you put so much effort into it?
And it seems like every time those questions start to be asked here, you show up and expend a lot of your energy writing long theoretical questions that sail right past real-world relevance off into fantasy land. The general answer to so many of your posts is: "No." No, there's no amount of power or antenna configuration that could make a MW signal usable halfway around the earth by a crystal radio locked inside a Faraday cage inside a salt mine. No, there's no way any receiver can produce armchair audio on a 1-watt station 1000 miles away that's co-channel to the 50 kW station next to which you've positioned your pocket receiver. Just...no. (And I think you know that, too, from the smiley faces that you've been putting at the end of some of these.)
You're a smart guy. That much is easy to tell from your posts. It should be obvious by now that among those of us who are still here on what's left of these boards, you're not getting much (if any) response anymore to these "way out there" scenarios. So maybe you can satisfy my curiosity, at least: why do you put so much effort into it?
And having said that, the OP deserves a real answer, too: yes, there are plenty of situations like that in the real world, though the limitation these days is much less atmospheric noise and much more ambient electrical noise.
Many of the former I-A clears still enjoy a situation like audioguy describes. You can drive KOA or WCCO or WGY right out to the very edge of bare intelligibility in most directions before you'll encounter anything co-channel, or even anything adjacent-channel to get in the way. Even in tighter parts of the country, ground conductivity often does the job: sure, it's only 350 miles or so from WABC in Lodi, NJ to co-channel WTOR up near me in Youngstown, NY...but several ranges of mountains and hills through upstate New York knock WABC down to nothing before it can get close to Youngstown.
Even some of the better - read, "older" - regional AMs can pull off the feat. You can drive WMT for many hours, right to the edge of its usable signal, before you hit any interference from the nearest co-channels to the east and south.
Many of the former I-A clears still enjoy a situation like audioguy describes. You can drive KOA or WCCO or WGY right out to the very edge of bare intelligibility in most directions before you'll encounter anything co-channel, or even anything adjacent-channel to get in the way. Even in tighter parts of the country, ground conductivity often does the job: sure, it's only 350 miles or so from WABC in Lodi, NJ to co-channel WTOR up near me in Youngstown, NY...but several ranges of mountains and hills through upstate New York knock WABC down to nothing before it can get close to Youngstown.
Even some of the better - read, "older" - regional AMs can pull off the feat. You can drive WMT for many hours, right to the edge of its usable signal, before you hit any interference from the nearest co-channels to the east and south.
I would expect that the now somewhat old X-Band would have a few of these such stations.
A somewhat disassociated problem would be what was programmed on them. In any case, the X-band
now is (and has been) available on the AM dial for a while. The owners of those licenses got a nice break that a heck of a lot of AM stations did not -- a pretty clear frequency, omni, and nice daytime power.
What they did with those desirable signals is another topic.
A somewhat disassociated problem would be what was programmed on them. In any case, the X-band
now is (and has been) available on the AM dial for a while. The owners of those licenses got a nice break that a heck of a lot of AM stations did not -- a pretty clear frequency, omni, and nice daytime power.
What they did with those desirable signals is another topic.
But the X-band stations don't go very far.
WMT is a good example of what the OP is talking about. Good day signal in all directions for well over 150 miles, although the Omaha 590 nips at it a little on its western fringe. The Chicago blowtorches are also a good example, although the sand dunes in southwest Michigan retard the signal somewhat going in that direction. The two best examples that come immediately to mind for me are perhaps, WBAP, KOA, KFYR, and CBW.
K
kenglish
Guest
I've seen a lot of reception Reports from Europe on WPTX.
I live in 700/WLW land.
Day and Night, WLW's signal travels unimpeded to the North and Northwest.
Days, there are stations to the east, though separated by mountains...in Mass, MD, and now NC. None of them in any way, restrict WLW's signal.
One daytime station in AL.
I suspect that with few exceptions, most of the former "clear channels" remain well protected during daylight hours.
Day and Night, WLW's signal travels unimpeded to the North and Northwest.
Days, there are stations to the east, though separated by mountains...in Mass, MD, and now NC. None of them in any way, restrict WLW's signal.
One daytime station in AL.
I suspect that with few exceptions, most of the former "clear channels" remain well protected during daylight hours.
It depends on what you mean by "well protected".
Way before the breakdown of the clears, WCBS had to deal with 880 in Columbus and WBAP with 820 in Chicago and WWL with Lansing. So there was some usage of the channels, albeit far away, going waaaaay back.
Now, the issue is both co-channel and adjacents. WABC has a co-channel NNE of Buffalo. KFI has a 50 kw on 650 in Sacramento and various 630's in NoCal, NV and elsewhere. Those cochannel and adjacents are affording the required daytime protection, so no harm is done.
The real issue today is the value of any listening outside the station's immediate metro. For regular ad sales, there is no real way to monetize out of market listening. The exception might be in the case of play by play sports, where the teams still see the advantage to having those big signals day and night... a real point in negotiating for the rights.
Don't disagree with anything above. My comments were written in response to the original poster's statement regarding co-channel.
By the way, I believe the first full-time station added on 700 KHZ was the Anchorage AK station, followed by a station in Colorado on the western side of the Rockies (now long gone).
WLW is pretty close to the most protected clear channel. Daytime, it comes in well into TN, and almost anywhere in the Ohio Valley. I hear stuff under it at night in Charleston, but never anything from inside the United States.
WWL is very well protected too. No other signal from TX to FL, with a daytimer in Charlotte, another in north Alabama, another one in the Tri-Cities area of TN, and another SW of Louisville the only other signals in the South there.
WWL is very well protected too. No other signal from TX to FL, with a daytimer in Charlotte, another in north Alabama, another one in the Tri-Cities area of TN, and another SW of Louisville the only other signals in the South there.
Co-channel interference does matter, and it matters a lot. Many AM signals are encroached upon even within their so-called primary coverage area such that the available signal-to-interference ratio is very poor, making for an unacceptable listening experience. Small-market stations seem to suffer the most in this regard. However, it is encouraging to hear that there are still a few stations that don't have to contend with high levels of interference.
Exactly the opposite is happening (slowly) on this side of the puddle.
Germany, for example, is switching off everything on all AM bands by the end of 2014 and spending the money on digital radio.
In Holland a major AM station switched off just the other week.
In the UK a number of smaller AM stations have gone off air and the BBC are phasing out local radio on AM (the nationals stay- for now)
The AM band is slowly getting clearer- if you can get away from the PLA and WiFi interference
Germany, for example, is switching off everything on all AM bands by the end of 2014 and spending the money on digital radio.
In Holland a major AM station switched off just the other week.
In the UK a number of smaller AM stations have gone off air and the BBC are phasing out local radio on AM (the nationals stay- for now)
The AM band is slowly getting clearer- if you can get away from the PLA and WiFi interference
Seems like WMT does get into SW Michigan in the daytime, but it is quite attenuated inland and gets adjacent channel interference from WKZO. At night, WMT has a shallow null to the East Northeast that originally protected stations on the East Coast. It comes in at night before sunset in Cedar Rapids, when WMT is supposed to go DA. It seems like the WMT signal is better at night recently than I ever remember though in Michigan.
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