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WHAM interference?
- Thread starter dustintv
- Start date
Or the staff trying to kill each other and someone left the mic on.
This on air "farting" was a common occurance for a spell about a decade ago. At the time WHAM engineers attributed it to "sunspot activity" and/or "solar flares"
You'll hear it during satellite fed programming, such as Paul Harvey.
I don't know if the sun is acting up with one of its periodic mood swings these days, but as I listen it sounds very much like what was happening back in those days I mentioned.
Of course, I'd never heard a similar problem on any other station airing the same programs, so I never really bought the whole "solar activity theory".
Whatever it is, it's annoying as all get out and I've found myself --as I did back then-- turning the dial because I just can't stand it !
You'll hear it during satellite fed programming, such as Paul Harvey.
I don't know if the sun is acting up with one of its periodic mood swings these days, but as I listen it sounds very much like what was happening back in those days I mentioned.
Of course, I'd never heard a similar problem on any other station airing the same programs, so I never really bought the whole "solar activity theory".
Whatever it is, it's annoying as all get out and I've found myself --as I did back then-- turning the dial because I just can't stand it !
Intermod products with a station(s) more local to Auburn?
BTW, solar outages are VERY real...we lost our NPR feed for 4 to 6 minutes a day for five days at the beginning of March, right at 2pm. I assume NPR/PRSS uses a different satellite than Paul Harvey, but I'd wager that whatever satellite they use, it's subject to the same problem for a few days every spring and fall. However, a solar outage typically means you suddenly hear a wash of static and/or "chirps" come in over a period of 30-60 seconds and then the signal is just plain gone for a few minutes, then the static/chirps for another 30-60 seconds and things are back to normal. If it's a digital feed like PRSS, then it drops out a few times for about 10 seconds before it disappears; the digital PRSS signal is quite robust...we still had it even when the stream decoders said Eb/No was only 3.5...but then it dropped below 3.0 and *poof* went the audio. Normal for us is about 13 or so.
FWIW, I have been surprised how "poorly" WHAM gets out there for a clear channeled Class A station. Driving down to Geneva from Rochester it's a dicey proposition east of the Clifton Springs thruway rest stop. And at night it's often a hashfest. Then again, in regards to Auburn, that *is* outside of WHAM's 2.5 mV/m contour...if there's mediocre ground conductivity between Rochester and Syracuse then it certainly wouldn't take much ambient radiofrequency interference to cause problems.
BTW, solar outages are VERY real...we lost our NPR feed for 4 to 6 minutes a day for five days at the beginning of March, right at 2pm. I assume NPR/PRSS uses a different satellite than Paul Harvey, but I'd wager that whatever satellite they use, it's subject to the same problem for a few days every spring and fall. However, a solar outage typically means you suddenly hear a wash of static and/or "chirps" come in over a period of 30-60 seconds and then the signal is just plain gone for a few minutes, then the static/chirps for another 30-60 seconds and things are back to normal. If it's a digital feed like PRSS, then it drops out a few times for about 10 seconds before it disappears; the digital PRSS signal is quite robust...we still had it even when the stream decoders said Eb/No was only 3.5...but then it dropped below 3.0 and *poof* went the audio. Normal for us is about 13 or so.
FWIW, I have been surprised how "poorly" WHAM gets out there for a clear channeled Class A station. Driving down to Geneva from Rochester it's a dicey proposition east of the Clifton Springs thruway rest stop. And at night it's often a hashfest. Then again, in regards to Auburn, that *is* outside of WHAM's 2.5 mV/m contour...if there's mediocre ground conductivity between Rochester and Syracuse then it certainly wouldn't take much ambient radiofrequency interference to cause problems.
Ground conductivity in Central and Western NY shouldn't be an issue for a 50kw NDA. The M-3 map shows it to be either 4 or 8, but it's well-known that in parts of suburban Rochester it's more like 15 in spots.
WHAM's antenna is an odd electrical height, something between quarter and half-wave. IIRC the nominal base impedance is some scary value like 300 ohms, which means the ATU is doing yeoman service to match the system to the 50-ohm Tx output.
Combined with the IBOC system the efficiency of the antenna may be compromised - certainly the station's telco-quality audio suggests bandwidth issues to me. So since this is the high-conductivity time of the year, as the snowpack melts in springtime, if WHAM's having close-in coverage problems I'd point to HD self-interference as a potential cause.
(Who saw THAT coming??) ;D ;D ;D
WHAM's antenna is an odd electrical height, something between quarter and half-wave. IIRC the nominal base impedance is some scary value like 300 ohms, which means the ATU is doing yeoman service to match the system to the 50-ohm Tx output.
Combined with the IBOC system the efficiency of the antenna may be compromised - certainly the station's telco-quality audio suggests bandwidth issues to me. So since this is the high-conductivity time of the year, as the snowpack melts in springtime, if WHAM's having close-in coverage problems I'd point to HD self-interference as a potential cause.
(Who saw THAT coming??) ;D ;D ;D
aaronread said:
All geosynchronous satellites are subject to solar outages, though at different times depending on their location in the belt. The precise symptoms depend on the type of signal being transmitted through the bird. (different types of digital transmission may behave differently etc.)
The sun radiates RF noise. The solar outages happen when the sun is directly behind the satellite - when your dish is pointed at the sun. The satellite may be a lot closer, but the sun is running a LOT more power
. A common workaround in TV is to temporarily uplink the same program to two different satellites for a week or two. You can predict when the outage is going to happen on one satellite and temporarily switch to the other one until it passes. I'm a bit surprised this doesn't seem to be common practice in radio. (I suppose too many stations only have one dish or don't have anyone around to switch dishes...)
That's mostly it...except for the largest stations, most NPR affiliates I know just have the one dish. Besides which, PRSS only operates on the one satellite. I suppose PRSS could light up a second satellite...but ignoring the cost of that for a moment, for a station to pay for, install, and maintain a second dish just to cover a grand total of perhaps one lost hour (at most) of programming in an entire year? The ROI just isn't there. And you can't realistically re-aim a single 3.8m dish fast enough...the outages are rarely more than 5-10 minutes, often only 2-4 mins.
Of course, that attitude bit a lot of people in the ass back in 1999 when Galaxy IV tumbled off into the ether and everyone lost their NPR feed for a day or two until a new bird could be acquired, lit up, and everyone re-aimed their dishes. Still, that was the first and, to my knowledge, only wide-scale long-term failure of the PRSS system. Pretty good operational record, I'd say.
I know some east coast stations will call up their counterparts on the opposite coast and arrange to receive a backup audio feed via ISDN and then reciprocate three hours later when the outage hits the west coast. But a lot of stations just put a notice on their website and otherwise ignore it; it's such a minor issue that it's not worth the hassle.
Is Radio Marti still running on 1180 am in Marathon Florida, targetting Cuba?
I live about 130 or so miles, due west from Rochester in south western Ontario and their night signal is iffy, at best.
FWIW. AM radio at night this winter as been awful. Aren't we coming up to the top of the sun spot cycle?
I live about 130 or so miles, due west from Rochester in south western Ontario and their night signal is iffy, at best.
FWIW. AM radio at night this winter as been awful. Aren't we coming up to the top of the sun spot cycle?
Judging from the posts in this thread I'd hazard a guess that the interference being heard is some local phenomenon. There has been a history of WHAM's having a ring of weak coverage typical of 50kw NDAs where the skywave cancels the groundwave but usually that manifests itself a lot closer in than 130 miles - more like about 50 to 70 miles.
I have experienced an actual A-B before-and-after demonstration of IBOC self-interference, though. Back in September when WBZ was cooperating with us on diagnosing the HD night interference, I was on a cellphone with WBZ's Engineering Manager one night. I was standing by the side of the road with good-quality headphones jacked into the FIM-41, taking a signal strength reading, at the moment the IBOC carrier was switched on. BZ was delivering a whopping skywave signal, IIRC on the order of 7 mv/m.
As the HD came on, the apparent loudless of the analog WBZ signal dropped very noticeably - I would guesstimate more than 6db. There was an obvious increase in a kind of mushy distortion, I would attribute it to a form of intermod products, which was quite unpleasant. But there was also an almost supersonic whistle present when HD was on - it sounded like the old TV horizontal-oscillator "wheeeen" you used to hear around CRT receivers. It was obvious that the COFDM was doing some very odd things bouncing around the 3DX-50 and the WBZ phasing and LTU components. And it wasn't good.
I certainly don't have any specifics to offer, but there have been reports here and elsewhere of odd self-interference cases cropping up from IBOC. Maybe this is another.
I have experienced an actual A-B before-and-after demonstration of IBOC self-interference, though. Back in September when WBZ was cooperating with us on diagnosing the HD night interference, I was on a cellphone with WBZ's Engineering Manager one night. I was standing by the side of the road with good-quality headphones jacked into the FIM-41, taking a signal strength reading, at the moment the IBOC carrier was switched on. BZ was delivering a whopping skywave signal, IIRC on the order of 7 mv/m.
As the HD came on, the apparent loudless of the analog WBZ signal dropped very noticeably - I would guesstimate more than 6db. There was an obvious increase in a kind of mushy distortion, I would attribute it to a form of intermod products, which was quite unpleasant. But there was also an almost supersonic whistle present when HD was on - it sounded like the old TV horizontal-oscillator "wheeeen" you used to hear around CRT receivers. It was obvious that the COFDM was doing some very odd things bouncing around the 3DX-50 and the WBZ phasing and LTU components. And it wasn't good.
I certainly don't have any specifics to offer, but there have been reports here and elsewhere of odd self-interference cases cropping up from IBOC. Maybe this is another.
Several years there was a daytime only station on 1180 near Cincinnati. On nights when the skip was good, WHAM blanketed the local just before the station signed off at sunset. Thats probably why they moved to 1160. The zone of interference for WHAM appears to go through Buffalo. Stations with interference zones closer in than WHAM are WWKB, WBZ, WSB and possibly KFI to the north. My observations may not be typical but were the case when I heard the stations. WLAC has an interference zone about 10 miles out from the XMTR probably due to the high frequency and poor ground conductivity in the area.
I know that historically WHAM's cancellation ring has been problematic in the cities of Syracuse to the east and Buffalo to the west, both around 70-80 miles distant. That's what I meant when I expressed doubt about a skywave-groundwave self-interference issue 130 miles away. The groundwave should be just about totally attentuated before 130 miles; the Canadian listener should be getting primarily skywave that far out.
WKBW/WWKB's skywave-groundwave clash is legendary within about 80-90 miles of the station, but it's generally manifested itself in an audio "phasing" effect instead of outright cancellation of the signal. The self-interference is apparently a result of the higher frequency and the electrical height of 1520's 3 towers, which were originally cut to be 1/4 wave radiators at KB's pre-NARBA frequency of 1480 kHz.
The "phasing" sounds like the signal is perpetually fed through an old Eventide Instant-Phaser, not unlike listening to music on shortwave. When KB was running C-QUAM the phasing led to some interesting stereo-platform effects, with the stereo image shifting first slowly, then more rapidly from side to side. If you were listening in a multi-speaker car system the image would rotate around the interior of the car in circular fashion, first slowly, then more rapidly, then slowing down and sometimes even reversing direction.
WKBW/WWKB's skywave-groundwave clash is legendary within about 80-90 miles of the station, but it's generally manifested itself in an audio "phasing" effect instead of outright cancellation of the signal. The self-interference is apparently a result of the higher frequency and the electrical height of 1520's 3 towers, which were originally cut to be 1/4 wave radiators at KB's pre-NARBA frequency of 1480 kHz.
The "phasing" sounds like the signal is perpetually fed through an old Eventide Instant-Phaser, not unlike listening to music on shortwave. When KB was running C-QUAM the phasing led to some interesting stereo-platform effects, with the stereo image shifting first slowly, then more rapidly from side to side. If you were listening in a multi-speaker car system the image would rotate around the interior of the car in circular fashion, first slowly, then more rapidly, then slowing down and sometimes even reversing direction.
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