That would seem to be the station at 1640AM - with an apparently unrestrained audio filter on their highs... I see spikes (on my just aquired RFSpace SDR-IQ) poking down (and up) well past the usual +/- 10kHz limits everyone else has to observe. Some go past 1615kHz (jutting into the EMS station run by the City of Berkeley at 1610). You can hear the "sizzle" of modulation peaks from the 1640 station when tuned to 1610. Are there different standards for broadcasters above 1600kHz?
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AM with widest bandwidth?
- Thread starter marshallstax
- Start date
Relative distances/powers to/between both stations and any particular measurement point makes such comparisions subject
to lots of consideration to figure out what the data means and whether conclusions regard listeners, stations,
or some other viewpoint.
Now this particular station?
They may not be aware if a filter designed to roll off highs has "degraded".
The only differences I know of are by a station's decision to follow various recommendations of the moment..
A standards commission is commissioned to create standards, not modify them to suit the whims of
speculators. The NRSC is apparently badly hearing-challenged. Whoever proposed and defined the AMAX
standards clearly was not hearing challenged.
A station is permitted to follow and operate by whatever parameters satisfy the FCC's requirements.
If the higher audio frequencies you measure are sufficiently " x db " below the carrier, they could be fine.
Low power 10w community and traffic AMs are limited to something like 2.5 khz brickwall.
No difference above 1600 except that any expansion of new stations up to 1710 WERE supposed to all be
the "somewhat" wideband CQUAM. This didn't happen and the spectrum is really no different 1600 up than any where
else on MW.
Part 15 AM is not required to limit high frequency response probably because the service area
(or interference, if you don't like it) is already well defined by the power levels.
Stations running AM iboc absolutely MUST brickwall analog at some ridiculously low frequency to leave
upper bandwidth areas of the signal clear for the ibiquity data to splatter about.
If I were running said station, I'd find some way to make the high frequency response better, too.
Hats off to whoever is willing to try to sound better.
You didn't mention at all how either station actually sounded on a radio.
If 1640 is really just screech and uncontrolled upper end trash, they deserve complaint letters.
Continued "garbage" operations are then worthy of complaining to FCC.
It doesn't sound like a bad station to me.
The question would be whether or not there is any degradation to the Berkeley signal within the area served.
Even if occasional peaks are heard in this service zone, whether they'd be buried by carrier is just something you'd have to
test by visiting there. I'd bet with a continuous-tuning radio you might hear the peaks of 1640 on the "upper" end of the
Berkeley signal, then less and less to almost no or no detection at all on the lower sideband of the 1610 station.
Bandwidth/selectivity/sensitivity of radios very all over the map, so it gets very fuzzy about whether
any station is splattering.
Modern receiver IF response on many cheap AM radios is so wide that almost every splatter complaint is baseless.
When a radio has no TUNED rf amp section for AM, and then has a ceramic filter thingy for the IF stage,
it takes us back to 1932 cheap table radio rf performance with whatever the modern manufacturer has decided to let the AM
have after having already done a barely tolerable job at the rf and if points of the process.
Too bad all receivers aren't required to comply with some meaningful standards.
At one time the market pushed crummy receivers out of use and superhets with razor sharp selection became the
winners ( and big names ) in the receiver industry.
All that's been thrown away for getting by with whatever is minimally acceptable.
to lots of consideration to figure out what the data means and whether conclusions regard listeners, stations,
or some other viewpoint.
Now this particular station?
They may not be aware if a filter designed to roll off highs has "degraded"
.The only differences I know of are by a station's decision to follow various recommendations of the moment..
A standards commission is commissioned to create standards, not modify them to suit the whims of
speculators. The NRSC is apparently badly hearing-challenged. Whoever proposed and defined the AMAX
standards clearly was not hearing challenged.
A station is permitted to follow and operate by whatever parameters satisfy the FCC's requirements.
If the higher audio frequencies you measure are sufficiently " x db " below the carrier, they could be fine.
Low power 10w community and traffic AMs are limited to something like 2.5 khz brickwall.
No difference above 1600 except that any expansion of new stations up to 1710 WERE supposed to all be
the "somewhat" wideband CQUAM. This didn't happen and the spectrum is really no different 1600 up than any where
else on MW.
Part 15 AM is not required to limit high frequency response probably because the service area
(or interference, if you don't like it) is already well defined by the power levels.
Stations running AM iboc absolutely MUST brickwall analog at some ridiculously low frequency to leave
upper bandwidth areas of the signal clear for the ibiquity data to splatter about.
If I were running said station, I'd find some way to make the high frequency response better, too.
Hats off to whoever is willing to try to sound better.
You didn't mention at all how either station actually sounded on a radio.
If 1640 is really just screech and uncontrolled upper end trash, they deserve complaint letters.
Continued "garbage" operations are then worthy of complaining to FCC.
It doesn't sound like a bad station to me.
The question would be whether or not there is any degradation to the Berkeley signal within the area served.
Even if occasional peaks are heard in this service zone, whether they'd be buried by carrier is just something you'd have to
test by visiting there. I'd bet with a continuous-tuning radio you might hear the peaks of 1640 on the "upper" end of the
Berkeley signal, then less and less to almost no or no detection at all on the lower sideband of the 1610 station.
Bandwidth/selectivity/sensitivity of radios very all over the map, so it gets very fuzzy about whether
any station is splattering.
Modern receiver IF response on many cheap AM radios is so wide that almost every splatter complaint is baseless.
When a radio has no TUNED rf amp section for AM, and then has a ceramic filter thingy for the IF stage,
it takes us back to 1932 cheap table radio rf performance with whatever the modern manufacturer has decided to let the AM
have after having already done a barely tolerable job at the rf and if points of the process.
Too bad all receivers aren't required to comply with some meaningful standards.
At one time the market pushed crummy receivers out of use and superhets with razor sharp selection became the
winners ( and big names ) in the receiver industry.
All that's been thrown away for getting by with whatever is minimally acceptable.
marshallstax said:
You don't talk about whether this is analog or IBOC. All I know about AM band bandwidth is about analog, and I don't remember any AF frequency restriction except that one station cannot interfere with another. Thus, in most markets AMs were historically spaced at least 30 kHz apart (Sacramento 1430 and 1470; Portland 1330, 1360, etc.)
But in Los Angeles because the region has so much population, AMs there were spaced 20kHz apart (LA region, 1240, 1260, 1280, 1300). At one point the FCC ordered KHJ to reduce its AF frequency response on 930 in order not to splatter a nearby station on either 910 or 950. Unfortunately, I forgot the offended station and the only station that seems to qualify is 950 in Tijuana, so either the offended station changed freqs at some point or it was TJ that was affected by KHJ. Regardless, at the time there was quite a bit of complaint that KHJ sounded muddy.
So, as far as I know (and feel free to correct me), most AMs are allowed to pass 15kHz (adjacent stations = 15kHz + 15kHz or 30kHz total between carrier freqs).
So, if the 1640 you mention is analog, it seems high fidelity (that is, 15kHz) audio bandwidth is perfectly legal.
On the AM broadcast band in the United States, maximum transmitted audio bandwidth is limited to 10.2 kHz by a National Radio Systems Committee (NRSC) standard adopted by the FCC in June 1989, resulting in a channel occupied bandwidth of 20.4 kHz.
The former audio limitation was 15 kHz resulting in a channel occupied bandwidth of 30 kHz.
The former audio limitation was 15 kHz resulting in a channel occupied bandwidth of 30 kHz.
The Wrench said:
Simon says: Remove your two smallest toes! Now! Pretend you never had them! Simon sez! Simon Sez!
Again: A capacitor somewhere must be drying up in the low pass network :
. Or the data collected any farther than 10.2 khz off 1640 is a stray iboc bit.
Couldn't possibly be a spur off analog modulation.
It's a LOT more likely to be an iboc bit that wandered away from the herd.
K
KRLA
Guest
The worst sounding station in the Bay Area is by far KNBR 680. Is it really worth the sound they have just to have the IBOC? The highest frequency KNBR broadcasts can't be higher than 4K. It used to be a great sounding station like KGO. It would be great to hear the Giants games again with good sound. It can be easily done.
At my loc in Berkeley KNBR (680) comes in awful - like I'm in the heart of a signal null or something... about 5k wide (5k out on either side of the carrier)KRLA said:
KCBS had its IBOC "rails" off yesterday... they're back on today, with their analog audio seemingly rolled back a bit... to about 8k or so
KGO has the "loudest" (heavily processed) sig... as fat & as wide as the law allows, just a hair past 10k.
Others:
560 - looks like it's to about 8k or a hair more... 8.5?
610 - clean and wide - 10.2k
860 - 10k and fat
910 - about 5.8k (satellite feed?)
960 - about 5k (satellite feed?) with IBOC rails
1050 - about 5k (satellite feed?) with IBOC rails
1100 - 10k
1260 - 10k
1310 - about 5.4 k (R. Disney satellite feed) with IBOC rails ("high side" rail looks weaker than low side rail - ??)
1400 - 10k and fat (processed hard)
1450 - about 5.8k (with a weird "carrier spike" at 6k out on the low side of their 1450 carrier with a much louder spike at 10k down - and another, not as strong, at 10k upside of their center freq.)
1510 - 10k
1550 - 10k
1640 - very fat and wide, as noted in earlier post... but their night sig, by contrast, is much lower and doesn't jut past 10k on either side of their carrier.
AM bandwidth is basically a function of frequency. At 540kHz, a 20.4kHz @ 100% AM modulation channel is roughly 4% of 540kHz. At 1,700kHz, a 20.4kHz channel @ 100% AM modulation is about 1% of 1,700kHz.
AM antennas are tuned by cancelling reactances at the carrier frequency. This results in the "pure" antenna resistance radiating all of the power on the carrier frequency. AM sidebands gain inductive reactance the higher they travel from the carrier. AM sidebands gain capacitive reactance the lower they travel from the carrier frequency. Reactance is not radiated, so the more reactance, the less signal is radiated. In AM, the sidebands are more reactive at higher audio frequencies, resulting in less radiation of the higher audio frequencies. An antenna system with better "bandwidth" is one with less reactance on either side of the carrier, allowing more radiation of those higher audio frequencies.
It is obviously much easier to obtain a flatter response at the higher frequencies. Tuning is much sharper at the lower frequencies. This results in circuit reactances having much more effect on the audio. Reactance at 4% from the carrier at 540kHz is much greater than the 1% at 1,700kHz.
The real "puppy" that many people fail to consider is the bandwidth of the IF circuitry in the AM receiver. This center IF frequencies are 450kHz (digital tuner) or 455kHz (analog tuner). These 20.4 kHz sidebands approach 5% of the IF frequency, resulting in very poor bandwidth of the IF stages. This manifests itself in poor high frequency audio response of many AM radios (regardless of any high quality transmitter signal) . Ceramic filters in AM IF circuits only worsen the condition.
AM digital HD has none of these problems that plague analog AM.
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AM antennas are tuned by cancelling reactances at the carrier frequency. This results in the "pure" antenna resistance radiating all of the power on the carrier frequency. AM sidebands gain inductive reactance the higher they travel from the carrier. AM sidebands gain capacitive reactance the lower they travel from the carrier frequency. Reactance is not radiated, so the more reactance, the less signal is radiated. In AM, the sidebands are more reactive at higher audio frequencies, resulting in less radiation of the higher audio frequencies. An antenna system with better "bandwidth" is one with less reactance on either side of the carrier, allowing more radiation of those higher audio frequencies.
It is obviously much easier to obtain a flatter response at the higher frequencies. Tuning is much sharper at the lower frequencies. This results in circuit reactances having much more effect on the audio. Reactance at 4% from the carrier at 540kHz is much greater than the 1% at 1,700kHz.
The real "puppy" that many people fail to consider is the bandwidth of the IF circuitry in the AM receiver. This center IF frequencies are 450kHz (digital tuner) or 455kHz (analog tuner). These 20.4 kHz sidebands approach 5% of the IF frequency, resulting in very poor bandwidth of the IF stages. This manifests itself in poor high frequency audio response of many AM radios (regardless of any high quality transmitter signal) . Ceramic filters in AM IF circuits only worsen the condition.
AM digital HD has none of these problems that plague analog AM.
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Would it also be accurate to describe temperature variations we experience as a plague?
Yes, audio response is different for upper and lower sidebands.
Daylight is "too red" at sunrise and sunset. This is not a plague, either.
If there IS a plague, it is AM radios which do not permit actaul tuning to the best balance given the available
bandwidth provided by whatever IF arrangement is provided.
Pretending "tuning" is something that happens in steps while disregarding IF characteristics
weakens greatly any claims about detriment to AM's situation regarding plague, response or anything.
Yes, audio response is different for upper and lower sidebands.
Daylight is "too red" at sunrise and sunset. This is not a plague, either.
If there IS a plague, it is AM radios which do not permit actaul tuning to the best balance given the available
bandwidth provided by whatever IF arrangement is provided.
Pretending "tuning" is something that happens in steps while disregarding IF characteristics
weakens greatly any claims about detriment to AM's situation regarding plague, response or anything.
marshallstax said:
That's most likely because you're sitting in a null of the directional pattern. Directional AM antennas have nulls that "move" as the frequency changes, and the HD carriers extend much further than even the widest analog AM. It's virtually impossible to keep a directional array accurate across 30 KHz.
Dave B.
iyiyi,
You made a good point.
Consider a directional at or near the bottom of the band with a bunch of deep nulls and five narrow 60° sticks shooting endfire straight into a populated area.
As one circumnavigates the array, they might beg God to stop playing with the EQ in their car stereo.
A Beat Frequency Oscillator might also be nice to have on board.
Many years ago, I was told that the best way to maintain the flattest audio response in all directions is to delay the RF to the various elements with cable as much as possible; only employ Eli, the Iceman to do the fine tuning.
You made a good point.
Consider a directional at or near the bottom of the band with a bunch of deep nulls and five narrow 60° sticks shooting endfire straight into a populated area.
As one circumnavigates the array, they might beg God to stop playing with the EQ in their car stereo.
A Beat Frequency Oscillator might also be nice to have on board.
Many years ago, I was told that the best way to maintain the flattest audio response in all directions is to delay the RF to the various elements with cable as much as possible; only employ Eli, the Iceman to do the fine tuning.
No more "rails" on the KCBS AM signal?
I've seen them gone before, briefly, only to return later... but the HD bands on either side of KCBS's 740AM signal have been gone for at least a day now... maybe longer. The modulation looks fat & wide right to the 10k limit.
Bay Area stations still showing HD "rails" on AM:
960
1050
1310
I'm using an RFSpace SDR-IQ with various software, including Spectravue, HDSDR v2.15, and SDR-Radio v1.5.
ps: 680 sounds a lot better than before, but still has a lo-fi 5k rolloff while most everyone else is out to about 10k (except for phone calls and some spots or satellite feeds)
I've seen them gone before, briefly, only to return later... but the HD bands on either side of KCBS's 740AM signal have been gone for at least a day now... maybe longer. The modulation looks fat & wide right to the 10k limit.
Bay Area stations still showing HD "rails" on AM:
960
1050
1310
I'm using an RFSpace SDR-IQ with various software, including Spectravue, HDSDR v2.15, and SDR-Radio v1.5.
ps: 680 sounds a lot better than before, but still has a lo-fi 5k rolloff while most everyone else is out to about 10k (except for phone calls and some spots or satellite feeds)
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