Since most Ancient Modulation stations don't have music formats, it probably doesn't matter to their listeners.
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Can AM reception in car radios be improved?
- Thread starter Santa fe
- Start date
Throughout the heyday of AM, including back in the 1950s, many radio sets including "large"models had less than two watts of audio power. This limited bass response, which could roll off starting around 100 to 150 Hz. Battery powered sets had even more of a power limitation to increase battery life. Sometimes there was just a tenth of a watt (100 mw) of audio output and the low frequency end could start rolling off around 250 Hz (near middle C on a piano). This was in addition to the limitation of small loudspeakers. Some sets with larger speakers did have a bit of bass boost but that could often be eliminated using the tone control so the radio could be played "louder" with less overload distortion. For any given AM/FM radio, the FM bass response was limited in the same manner as for AM.
For treble, the audio circuits might go up to 15 KHz (the FM standard) but AM response depends on the tuning circuits. Although the (U.S.) AM channel allows response up to 5 KHz, rolloff may begin somewhat before, say, 3-1/2 KHz since inexpensive analog tuning circuits could not achieve a sharp cutoff.to adequately limit adjacent channel pickup at night.
Overall, car radios were more likely than home radios to have a tuned RF stage on AM, which greatly improves sensitivity and selectivity. This is not specifically advertised so the only way to find out is to try out the radio.
For treble, the audio circuits might go up to 15 KHz (the FM standard) but AM response depends on the tuning circuits. Although the (U.S.) AM channel allows response up to 5 KHz, rolloff may begin somewhat before, say, 3-1/2 KHz since inexpensive analog tuning circuits could not achieve a sharp cutoff.to adequately limit adjacent channel pickup at night.
Overall, car radios were more likely than home radios to have a tuned RF stage on AM, which greatly improves sensitivity and selectivity. This is not specifically advertised so the only way to find out is to try out the radio.
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That's actually a myth. AM stations in North America are allowed to transmit with an audio bandwidth of up to 10 kHz. And prior to the implementation of the NRSC bandwidth standard in the early 1990s, they were allowed up to 15 kHz audio bandwidth, the same as FM.
Most older AM radios had a fairly broad bandwidth and relied mostly on the tone control and speaker to roll off the highs. It was the introduction of ceramic filters and digital tuning in the 1980s when many AM radios started to drastically reduce their bandwidth.
The HD Radio in my 2013 Ford Escape is capped at 5 KHz on AM, so that the sidebands of the HD Radio carrier are filtered out. Unfortunately, this also applies to stations that are not transmitting the carrier, so all stations are limited to 5 KHz, making music formatted stations sound dull and muffled. Not sure why they couldn't design the radio to automatically filter out the HD carrier, or provide an option to toggle between a full response or a 5 KHz low pass.
I found a tape that I recorded on an old Sony CFD-(can't remember the number) that was made in the late 80's/early 90's, and the AM station that was on it sounded pretty good. Digitizing the tape and analyzing it showed frequency peaks reaching 10 KHz, so the radio must have been capable of wide band reception. All other radios that I used capped the frequency response of AM to around 8 KHz, which isn't very noticeable, unless one knows what they are listening for. 5 KHz was an obvious difference.
I found a tape that I recorded on an old Sony CFD-(can't remember the number) that was made in the late 80's/early 90's, and the AM station that was on it sounded pretty good. Digitizing the tape and analyzing it showed frequency peaks reaching 10 KHz, so the radio must have been capable of wide band reception. All other radios that I used capped the frequency response of AM to around 8 KHz, which isn't very noticeable, unless one knows what they are listening for. 5 KHz was an obvious difference.
Are you sure that's not a rear window defroster built into the back glass?
Many new cars use the rear defroster grid as the antenna.
I was driving on a street with a light rail in the median in Charlotte and the one good radio station there formatwise got messed up by it.
That is common. Along the above-ground Metrolink commuter rail lines in Los Angeles where they use the median strip of "freeways" the lines themselves radiate noise that sometimes can be heard under even 50 kw KFI and which overpowers all AM when a train goes by.
One of my Sony pocket radios (sadly no longer in use after dropping it too many times) had a wide enough bandwidth to pick up the edges of the IBOC sidebands on AM stations. I really noticed it one day in Indianapolis, trying to tune in WIBC 1070 to make a proper recording (it was a pocket AM-FM stereo cassette recorder, a real gem). Tuned dead in the middle, the IBOC hash was there. Tune to either side, and it was really there. On any local non-IBOC station, the AM fidelity was great.
Pretty much with any of my AM radios, no matter how perfect I had the station dialed in, I could still hear the waterfall effect of the HD Radio/IBOC carrier bleeding in from the sidebands. As mentioned before, some radios limited the AM bandwidth to 5 KHz to filter out the carrier for a cleaner broadcast, but it also meant that all stations, even if they they didn't broadcast an IBOC carrier, would be reduced to 5 KHz as well.
Any AM station carrying a HD Radio feed had to cut their bandwidth down from 10 KHz to 5 KHz so that the center frequency would not interfere with the sidebands (or adjacent frequencies) on which the carrier broadcasted on, hence the reduced fidelity. Otherwise, those higher end frequencies would interfere with the carrier and would essentially make decoding impossible. Also, since the carrier is transmitted on the adjacent frequencies, (example: AM 1260 would use AM 1250 & AM 1270 to transmit the IBOC), some stations were not able to transmit in HD, or limited it to the daytime as the carrier would cause interference to stations on adjacent frequencies, both in nearby areas and skywave, leading to some stations filing complaints. The opposite could also happen, leading to a distant station interfering with one of the carriers of a local station at night.
I remember reading several years ago about the IBOC sidebands from KDKA in Pittsburgh (1010 and 1030) interfering with the analog signals from WINS New York and WBZ Boston in their own markets, and vice versa, with their IBOC carriers tearing up KDKA's 1020 analog signal in suburban Pittsburgh.
Here in Phoenix, the lower IBOC sideband from KNX 1070 Los Angeles would completely wipe out local KDUS on 1060, 350 miles away, and probably didn't do KRLD Dallas any favors on 1080. AM IBOC was always a bad idea.
@ajaynejr
Somehow, through my finger-painting thrashes through electronics, I had picked up about outdoor diamond-shaped loop antennae for AM, with a basic pulley and rope to swing it, using fixed capacitors at 600, 1000 and 1400 kHz situated throughout the loop windings, done that way so someone INSIDE didn't have to manually adjust a variable capacitor for resonance.
So I venture that older AM car radios were pre-primed much the same way?
I do remember punching up car buttons that weren't 'set' yet and seeing the dial indicator stopping at basically those same spots.
Fine reading there. Thanks !
Somehow, through my finger-painting thrashes through electronics, I had picked up about outdoor diamond-shaped loop antennae for AM, with a basic pulley and rope to swing it, using fixed capacitors at 600, 1000 and 1400 kHz situated throughout the loop windings, done that way so someone INSIDE didn't have to manually adjust a variable capacitor for resonance.
So I venture that older AM car radios were pre-primed much the same way?
I do remember punching up car buttons that weren't 'set' yet and seeing the dial indicator stopping at basically those same spots.
Fine reading there. Thanks !
My thoughts-
1. Performance of entertainment electronics in a vehicle is a business decision by the vehicle manufacturer. If enough customers want something, and providing it is profitable, the manufacturer will consider it and perhaps do it.
2. Intensity of environmental sources of interference to communications is determined by market forces, economic and political compromise.
For example:
Copper ethernet networks are clearly of greater value to society than preserving a low environmental noise floor for AM radio reception. Our computer networks are more important than radio reception.
Given how the general public is outraged over increases in electrical bills, what is the likelihood electric utilities will take steps to clean up interference caused by power lines? Presently it is zero. Understand that much of electrical distribution is designed in a way that is not engineering elegance. Specifically, much residential street distribution is unbalanced. Think about the implications of that. Considering that utilities have to be pressured or regulated simply to put spark shields on their fuses to reduce the chance of forest fires that can kill people, they are not going to clean up radiated interference from their lines.
Utilites are not going to spend billions of dollars reducing interference caused by their power distribution system. They are focused on acceptable performance at lowest cost. Have you ever looked at the KVA rating of your neighborhood pole mounted transformer, counted the houses and done the math? Am I missing something about the posted specs? I hate to go off on the electric utilities but look at how they engineer their systems. And they do it in plain sight. Consumers spend billions on surge protectors largely because the utilities can't be bothered to improve power quality.
3. Echoing what kevtronics posted- The AM system is capable of full-fidelity mono sound with frequency response beyond 15 kHZ at low distortion that most people won't notice. The sound of AM radio heard on radios is a result of #1 and #2 above. The bad sound is not caused by AM itself, but rather by market forces that resulted in creation of terrible sounding radios.
I will now be snarky and say those of you who say AM radio sounds awful have never heard audio from a modulation monitor at the transmitter site. Especially before the focus on occupied radiofrequency bandwidth, and the misguided, almost neurotic obsession with the NRSC curve and filter. Think about it, no competent AM engineer will broadcast significant audio level beyond 10 KHz anyway, because you can't push it through receivers that are down 40 dB at those frequencies.
Shame on you people who bad mouth AM. You have never heard AM. You heard the bastardization of it by receiver manufacturers driven by consumer choices. AM sound quality was ruined on the back end by receivers, and on the front end by some, but not all broadcasters who did not respect or were unwilling to accept realities of radio wave propagation at the frequencies chosen for AM broadcasting.
AM is a great system for mono audio broadcasting, economically delivered. As a creator of audio content for a local area, think about the implications of paying the internet dope dealer a fee for every streaming listener, compared to the freedom and confidentiality of broadcasting to all with a fixed operational cost.
Support radio broadcasting. It has value and independence, the free broadcast press.
1. Performance of entertainment electronics in a vehicle is a business decision by the vehicle manufacturer. If enough customers want something, and providing it is profitable, the manufacturer will consider it and perhaps do it.
2. Intensity of environmental sources of interference to communications is determined by market forces, economic and political compromise.
For example:
Copper ethernet networks are clearly of greater value to society than preserving a low environmental noise floor for AM radio reception. Our computer networks are more important than radio reception.
Given how the general public is outraged over increases in electrical bills, what is the likelihood electric utilities will take steps to clean up interference caused by power lines? Presently it is zero. Understand that much of electrical distribution is designed in a way that is not engineering elegance. Specifically, much residential street distribution is unbalanced. Think about the implications of that. Considering that utilities have to be pressured or regulated simply to put spark shields on their fuses to reduce the chance of forest fires that can kill people, they are not going to clean up radiated interference from their lines.
Utilites are not going to spend billions of dollars reducing interference caused by their power distribution system. They are focused on acceptable performance at lowest cost. Have you ever looked at the KVA rating of your neighborhood pole mounted transformer, counted the houses and done the math? Am I missing something about the posted specs? I hate to go off on the electric utilities but look at how they engineer their systems. And they do it in plain sight. Consumers spend billions on surge protectors largely because the utilities can't be bothered to improve power quality.
3. Echoing what kevtronics posted- The AM system is capable of full-fidelity mono sound with frequency response beyond 15 kHZ at low distortion that most people won't notice. The sound of AM radio heard on radios is a result of #1 and #2 above. The bad sound is not caused by AM itself, but rather by market forces that resulted in creation of terrible sounding radios.
I will now be snarky and say those of you who say AM radio sounds awful have never heard audio from a modulation monitor at the transmitter site. Especially before the focus on occupied radiofrequency bandwidth, and the misguided, almost neurotic obsession with the NRSC curve and filter. Think about it, no competent AM engineer will broadcast significant audio level beyond 10 KHz anyway, because you can't push it through receivers that are down 40 dB at those frequencies.
Shame on you people who bad mouth AM. You have never heard AM. You heard the bastardization of it by receiver manufacturers driven by consumer choices. AM sound quality was ruined on the back end by receivers, and on the front end by some, but not all broadcasters who did not respect or were unwilling to accept realities of radio wave propagation at the frequencies chosen for AM broadcasting.
AM is a great system for mono audio broadcasting, economically delivered. As a creator of audio content for a local area, think about the implications of paying the internet dope dealer a fee for every streaming listener, compared to the freedom and confidentiality of broadcasting to all with a fixed operational cost.
Support radio broadcasting. It has value and independence, the free broadcast press.
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Actually utilities should be out there repairing the problems because it prevents damage down the line. If the insulators are arcing eventually they will fail causing major damage. I used to work for a public utility and I was their main RFI TVI investigator and spent thousands of hours out in the field troubleshooting issues. Anything that causes an arc is lost energy along the line. That means less revenue for the power company.. So repairing the problem and correcting the issue is actually more beneficial to them than you think.
AM radio, especially in stereo, can equal FM in sound quality. It's not the mode of transmission, it's the stinking receivers! They need to be improved drastically and there's no reason why they cannot be economically. It's time to push the manufacturers to produce a better AM radio section other than the crap that they currently turn out
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In my earlier lifetime I had the impression that car radios (AM only; the tube/vibrator kind and early solid state using single (single ended) class A output stage TO-3 transistor) had poorer treble response. (I did not have any test equipment back then) This I attributed to the sharper tuning circuits (which improved nighttime selectivity). The loss of treble was collateral damage.
The tone control was a traditional treble cut control in the audio circuitry (adding insult to injury?) .
My father saved one for me when trading in the family car. I put the radio, minus the vibrator, in a primitive cabinet (a cardboard box) and fed it with an old AC output toy train transformer (whose output mimicked the vibrator output).
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The tone control was a traditional treble cut control in the audio circuitry (adding insult to injury?) .
My father saved one for me when trading in the family car. I put the radio, minus the vibrator, in a primitive cabinet (a cardboard box) and fed it with an old AC output toy train transformer (whose output mimicked the vibrator output).
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I mean to say over the air broadcasting is the audio and video content essence of American values of independence, freedom, personal privacy and free speech, confidentially heard and viewed. Members of the political and cultural constituency that prioritize these ideas might consider listening and viewing over the air broadcasting more, and the internet less. Over the air broadcasting is part of the heart and soul of American values. Much of the conflict over the internet is the gatekeeper of the network and listening/viewing device.
If Americans value their freedom, they should support over the air broadcasting. The internet has theoretically unlimited independent voices, but we see that all of them are potentially subject to control. Yes, over the air broadcasting is regulated by the government, but the delivery path and receiving devices are not, so far. Maintaining the freedom of broadcast content delivery and consumption is in the hands of the public, if they can just put down those phones and think.
Please don't misunderstand my comments. I love our country and I love radio.
If Americans value their freedom, they should support over the air broadcasting. The internet has theoretically unlimited independent voices, but we see that all of them are potentially subject to control. Yes, over the air broadcasting is regulated by the government, but the delivery path and receiving devices are not, so far. Maintaining the freedom of broadcast content delivery and consumption is in the hands of the public, if they can just put down those phones and think.
Please don't misunderstand my comments. I love our country and I love radio.
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Continuouswave- thank you for contributing. "From what I have read" overall efficiency of the utility distribution system is about 95 percent, and less during time of heavy load. And the margin between long term average consumption and available production can be less that 5 percent. If this is correct, these are horrible metrics. Imagine if at 55 mph your car was at 95 percent of redline RPM.
So, in high demand power company voltage sags, as a result of their design choices. Thus, I endure a rolling blackouts and have to either buy a generator or pay to replace spoiled groceries. And they still send me an electric bill.
I apologize for ranting. Electric utilities put their mess out there on the street, and I can't help but notice it. People go nuts over a cell tower or red lights on a tower, but this electric power train wreck has been up for decades.
On my street one 15 KVA pole transformer feeds four houses, and two of them are big houses. Someone tell me why this is not a problem.
So, in high demand power company voltage sags, as a result of their design choices. Thus, I endure a rolling blackouts and have to either buy a generator or pay to replace spoiled groceries. And they still send me an electric bill.
I apologize for ranting. Electric utilities put their mess out there on the street, and I can't help but notice it. People go nuts over a cell tower or red lights on a tower, but this electric power train wreck has been up for decades.
On my street one 15 KVA pole transformer feeds four houses, and two of them are big houses. Someone tell me why this is not a problem.
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From building some AM radio kits eons ago, I do recall that 600, 1000, and 1400 were the frequencies used for alignment adjustments, or at least close by. It is possible that the car radios were preset with those frequencies at the factory to make that process more efficient.
The 15 KVA transformer delivers up to about 62 amps at 240 volts (at the transformer secondary) to all 4 houses combined.
Most of the time the total draw is much less.
If the transformer is significantly overloaded then the fuse at its primary terminal will blow. Then the power company has to send someone out to change the fuse and records can be kept to determine when and where a bigger transformer is needed.
(see the engineering report in post #16)
Kirk Bayne
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