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Car Radios: Why is the reception so good...
as compared to my home radios/stereos?
All-- Have wondered for years why this is so--almost w/o exception, on both AM/FM. On the car NGs, it was suggested that my house was blocking signals, and that the metallic car acted as a big antenna. Neither seems plausible, as my car next to the shop radio (which is terrible) still gets good reception, and that if the metal in a car were so good, you wouldn't need a car antenna. I'm thinking it's the actual electronics. Any opinions/explanations? ---------------------------- Mr. P.V.'d formerly Droll Troll |
Car radios (at least back in the tube era) were generally superior
to most inexpensive home radios. They included a tuned RF stage which gave them the extra ooomph. The tube auto radios had the antenna as part of the tuned circuit (coupled to the high impedance point of the RF stage), so they worked somewhat like a tuned active antenna. Peter "Proctologically Violated©®" wrote in message ... as compared to my home radios/stereos? All-- Have wondered for years why this is so--almost w/o exception, on both AM/FM. On the car NGs, it was suggested that my house was blocking signals, and that the metallic car acted as a big antenna. Neither seems plausible, as my car next to the shop radio (which is terrible) still gets good reception, and that if the metal in a car were so good, you wouldn't need a car antenna. I'm thinking it's the actual electronics. Any opinions/explanations? ---------------------------- Mr. P.V.'d formerly Droll Troll |
Behold, Proctologically Violated©® signalled from keyed 4-1000A filament:
as compared to my home radios/stereos? All car radio's use an actual antenna to receive signals. Many home stereo's don't even have a connection for an external antenna anymore....they're mostly just vapourware. -- Gregg t3h g33k "Ratings are for transistors....tubes have guidelines" http://geek.scorpiorising.ca |
"Proctologically Violated©®" wrote in message ... as compared to my home radios/stereos? Have wondered for years why this is so--almost w/o exception, on both AM/FM. Since cars drive through all the poor reception areas as well as good places, there is a strong incentive to build their radios to have good performance. These days the weak-signal performance of the AM side of car radios is degraded, since RF noise levels are so high. It's cheaper to degrade the radio than to further suppress the noise the car makes - and anyway power lines, etc., are pretty noisy. But the FM sections are generally very good. The ordinary plastic-box home radio or all-in-one system has a VERY cheap radio. Your expensive hi-fi probably has a good FM section, but most are very poor on AM. It's all a matter of design and perception of what the listener will tolerate. No sense building a wondrous radio if most buyers don't care and wouldn't want to pay what it would cost.. |
In article HbA5d.298202$Lj.253385@fed1read03, " Uncle Peter" wrote:
Car radios (at least back in the tube era) were generally superior to most inexpensive home radios. They included a tuned RF stage which gave them the extra ooomph. The tube auto radios had the antenna as part of the tuned circuit (coupled to the high impedance point of the RF stage), so they worked somewhat like a tuned active antenna. Peter Another reason was the lower IF -- generally 265 kHz vs. the 455 kHz used in home sets. This allowed a more selective IF -- smaller bandwidth for the same Q -- so the adjacent channel interference was cut dow. Some MW [BCB] DXers would use car radios set up for home use for just that reason. Dr. G. "Proctologically Violated©®" wrote in message ... as compared to my home radios/stereos? All-- Have wondered for years why this is so--almost w/o exception, on both AM/FM. On the car NGs, it was suggested that my house was blocking signals, and that the metallic car acted as a big antenna. Neither seems plausible, as my car next to the shop radio (which is terrible) still gets good reception, and that if the metal in a car were so good, you wouldn't need a car antenna. I'm thinking it's the actual electronics. Any opinions/explanations? ---------------------------- Mr. P.V.'d formerly Droll Troll |
Appreciate the, uh, feedback. It's sort of as I thought.
Altho I also think it's a CableTV conspiracy. Now, if I could find a car radio w/ a pre-amp output, I'd just plug it in to my crappy stereo's aux. input! ---------------------------- Mr. P.V.'d formerly Droll Troll "Proctologically Violated©®" wrote in message ... as compared to my home radios/stereos? All-- Have wondered for years why this is so--almost w/o exception, on both AM/FM. On the car NGs, it was suggested that my house was blocking signals, and that the metallic car acted as a big antenna. Neither seems plausible, as my car next to the shop radio (which is terrible) still gets good reception, and that if the metal in a car were so good, you wouldn't need a car antenna. I'm thinking it's the actual electronics. Any opinions/explanations? ---------------------------- Mr. P.V.'d formerly Droll Troll |
Proctologically Violated©® wrote:
Appreciate the, uh, feedback. It's sort of as I thought. Altho I also think it's a CableTV conspiracy. Now, if I could find a car radio w/ a pre-amp output, I'd just plug it in to my crappy stereo's aux. input! ---------------------------- Mr. P.V.'d formerly Droll Troll You may have trouble finding one with a pre-amp output, but most of the new ones have "line level" outputs. That's what many of them use to drive those gigawatt bass amplifiers, so they can shake the rust off of their car. -- Martin E. Meserve - K7MEM http://www.k7mem.150m.com |
#1 reason is the Antenna. #2 cost is king!
Car = antenna on AM & FM Home radio = Bar antenna on AM and ? what on FM... Sometimes it is the power cord. Sometimes you have a wire to drape over the lamp shade. The aluminum backing on house insulation can provide some attenuation effect, but I'm sure this is less of a factor...it is the primarily the antenna. Car radios on FM do not have exceptional selectivity as speculated above. The adjacent channel selectivity is only fair and the systems are made to only use alternate channels in any one market, anyway. When you're between markets and have a weak station 200 KHz away from a strong one that you have trouble. If "they" wanted better performance @ home is could be done, just costs $$. Low IF for reduced BW can be done in any radio, but size and Q and frequency are not independent, so lower freq IF means bigger coils and more "R", so "same Q - lower IF" is not that simple. Did you hear about that guy who changed his name to "They". Interview on pub radio this weekend. "Proctologically Violated©®" wrote in message ... as compared to my home radios/stereos? All-- Have wondered for years why this is so--almost w/o exception, on both AM/FM. On the car NGs, it was suggested that my house was blocking signals, and that the metallic car acted as a big antenna. Neither seems plausible, as my car next to the shop radio (which is terrible) still gets good reception, and that if the metal in a car were so good, you wouldn't need a car antenna. I'm thinking it's the actual electronics. Any opinions/explanations? ---------------------------- Mr. P.V.'d formerly Droll Troll |
"Steve Nosko" wrote in message ... Low IF for reduced BW can be done in any radio, but size and Q and frequency are not independent, so lower freq IF means bigger coils and more "R", so "same Q - lower IF" is not that simple. It must be a couple of decades since IF bandwidth depended on "real" IF coils and their Q. Since then mechanical [ceramic] filters have set the bandwidth of essentially all consumer radios known to me. OK there are now a few high-end DSP-based radios. Those too-narrow IFs in today's AM radios come from ceramic filters, not low freq IF. |
"Steve Nosko" wrote in message ... #1 reason is the Antenna. #2 cost is king! Car = antenna on AM & FM Home radio = Bar antenna on AM and ? what on FM... Sometimes it is the power cord. Sometimes you have a wire to drape over the lamp shade. The aluminum backing on house insulation can provide some attenuation effect, but I'm sure this is less of a factor...it is the primarily the antenna. Car radios on FM do not have exceptional selectivity as speculated above. The adjacent channel selectivity is only fair and the systems are made to only use alternate channels in any one market, anyway. When you're between markets and have a weak station 200 KHz away from a strong one that you have trouble. If "they" wanted better performance @ home is could be done, just costs $$. Low IF for reduced BW can be done in any radio, but size and Q and frequency are not independent, so lower freq IF means bigger coils and more "R", so "same Q - lower IF" is not that simple. Selectivity is easier for FM since they can use inexpensive ceramic filters instead of IF transformers. Unfortunately, instead of going a few pennies more for DECENT filters, they use the cheapest they can get away with. Peter Pete |
"R J Carpenter" wrote in message ...
"Steve Nosko" wrote in message ... Low IF for reduced BW can be done in any radio, but size and Q and frequency are not independent, so lower freq IF means bigger coils and more "R", so "same Q - lower IF" is not that simple. It must be a couple of decades since IF bandwidth depended on "real" IF coils and their Q. Since then mechanical [ceramic] filters have set the bandwidth of essentially all consumer radios known to me. OK there are now a few high-end DSP-based radios. Those too-narrow IFs in today's AM radios come from ceramic filters, not low freq IF. A decent car radio in FM isn't anymore selective or sensitive than a decent home stereo tuner or receiver in FM. The reason a car radio sounds cleaner on weaker FM stations has more to do with the stereo mpx circuit. All car radios have a circuit in the mpx circuit that blends the stereo-to-mono and mono-to-stereo mode. When manually set in FM mono mode on a home stereo the SNR is better than in stereo mode on weak stations. The same holds true for an FM car radio. The only difference is car radios don't have mono switches. Instead, internal to the FM car tuner is a circuit that blends the stereo/mono mode so when the car is in motion and signal strength is varying all over the place the tuner isn't constantly and abruptly switching between stereo and mono. Also in this blend circuit is an RC time constant that "smooths" out the blending action. So somewhere a happy medium is established and a relative slowly changing SNR takes place slow enough to be unnoticable. In other words, if far enough from a station the car radio isn't in 100% stereo mode. It's some where between stereo and mono. If you're right near the broadcast antenna SNR is best as well as full stereo separation. |
After seeing all these replies here, I think one point stands out 5x9 - do
not use an integrated receiver at home, but components. -- Gregg t3h g33k "Ratings are for transistors....tubes have guidelines" http://geek.scorpiorising.ca |
OEM car radios are pretty much state-of-the-art design. They always have
been. Today's models have ceramic IF filters, up conversion on AM, noise blankers, audio DSP.... The next generation will have digital IF. For some reason automakers have always been real picky about radio performance, and willing to pay for it! (Been in the OEM automotive radio design biz for 30 years.) Bob D. "Steve Nosko" wrote in message ... #1 reason is the Antenna. #2 cost is king! Car = antenna on AM & FM Home radio = Bar antenna on AM and ? what on FM... Sometimes it is the power cord. Sometimes you have a wire to drape over the lamp shade. The aluminum backing on house insulation can provide some attenuation effect, but I'm sure this is less of a factor...it is the primarily the antenna. Car radios on FM do not have exceptional selectivity as speculated above. The adjacent channel selectivity is only fair and the systems are made to only use alternate channels in any one market, anyway. When you're between markets and have a weak station 200 KHz away from a strong one that you have trouble. If "they" wanted better performance @ home is could be done, just costs $$. Low IF for reduced BW can be done in any radio, but size and Q and frequency are not independent, so lower freq IF means bigger coils and more "R", so "same Q - lower IF" is not that simple. Did you hear about that guy who changed his name to "They". Interview on pub radio this weekend. "Proctologically Violated©®" wrote in message ... as compared to my home radios/stereos? All-- Have wondered for years why this is so--almost w/o exception, on both AM/FM. On the car NGs, it was suggested that my house was blocking signals, and that the metallic car acted as a big antenna. Neither seems plausible, as my car next to the shop radio (which is terrible) still gets good reception, and that if the metal in a car were so good, you wouldn't need a car antenna. I'm thinking it's the actual electronics. Any opinions/explanations? ---------------------------- Mr. P.V.'d formerly Droll Troll |
Hi!
In many European contries we have DAB (DIGITAL) transmissions, mostly along the main roads. I got my last car radio with DAB and also FM. You select a station and there it is, whithout any fallouts or noise on the whole trip, for instance from Oslo to Trondheim. Some entusiast complains about the compression, it is like MP3, but most people find the quality sufficiently good. If the DAB signal falls out, the FM takes over. It is also a very good FM-receiver. I very often listen to a station sending only classical music. Few FM stations relay that program, but with DAB you have it crystal clear all the time! Is something similar coming stateside? Alf "Bob D." skrev i melding news:2rHad.113885$He1.9393@attbi_s01... OEM car radios are pretty much state-of-the-art design. They always have been. Today's models have ceramic IF filters, up conversion on AM, noise blankers, audio DSP.... The next generation will have digital IF. For some reason automakers have always been real picky about radio performance, and willing to pay for it! (Been in the OEM automotive radio design biz for 30 years.) Bob D. "Steve Nosko" wrote in message ... #1 reason is the Antenna. #2 cost is king! Car = antenna on AM & FM Home radio = Bar antenna on AM and ? what on FM... Sometimes it is the power cord. Sometimes you have a wire to drape over the lamp shade. The aluminum backing on house insulation can provide some attenuation effect, but I'm sure this is less of a factor...it is the primarily the antenna. Car radios on FM do not have exceptional selectivity as speculated above. The adjacent channel selectivity is only fair and the systems are made to only use alternate channels in any one market, anyway. When you're between markets and have a weak station 200 KHz away from a strong one that you have trouble. If "they" wanted better performance @ home is could be done, just costs $$. Low IF for reduced BW can be done in any radio, but size and Q and frequency are not independent, so lower freq IF means bigger coils and more "R", so "same Q - lower IF" is not that simple. Did you hear about that guy who changed his name to "They". Interview on pub radio this weekend. "Proctologically Violated©®" wrote in message ... as compared to my home radios/stereos? All-- Have wondered for years why this is so--almost w/o exception, on both AM/FM. On the car NGs, it was suggested that my house was blocking signals, and that the metallic car acted as a big antenna. Neither seems plausible, as my car next to the shop radio (which is terrible) still gets good reception, and that if the metal in a car were so good, you wouldn't need a car antenna. I'm thinking it's the actual electronics. Any opinions/explanations? ---------------------------- Mr. P.V.'d formerly Droll Troll |
Alf Jacob Munthe wrote:
Is something similar coming stateside? Kinda, sortagrin. The USA is deploying something called "In Band On Channel" (IBOC), or "HD Radio". This scheme allows stations to broadcast a digital signal over the same frequency as their analog broadcasts. (more accurately, for FM stations the digital signal is broadcast in the "guard band" at the outer edge of the analog FM signal; for AM/MW stations it's broadcast in the four channels adjacent to the analog signal. For that reason, many call it "In Band Adjacent Channel"/IBAC!) Yes, the U.S. is trying to do digital radio on MW. All U.S. analog stations are authorized to begin IBOC digital broadcasts; they need only notify the government upon turning on the digital transmitter. There are a few (30-40?) FM stations known to be operating digitally, and maybe a dozen MW stations. MW stations, however, are only allowed to operate their digital transmitters during the daytime. There are fears (justified, IMHO) that nighttime MW digital will cause ruinous interference to existing analog MW reception. There is one IBOC test station operating, on MW, in Mexico City. To my knowledge it's the ONLY IBOC station outside the United States. Even Canada has gone with the European Eureka system. [0] It is widely believed that the U.S. has gone with IBOC for strictly political reasons - owners of powerful analog stations are unwilling to face additional competition from low-powered analog stations that suddenly acquire citywide coverage areas on Eureka multiplexes, and from formerly-MW stations that suddenly acquire high-fidelity digital sound. The ability to receive a single program during a long trip in the U.S. will probably never happen via terrestrial radio. [1] A U.S. broadcasting license conveys authority for only a single transmitter, and until recently it was illegal for one company to own enough transmitters to cover the entire country. (or even half of it) For that reason, while I've logged over 1,200 FM stations here, I've *never* seen one using the RDS "alternate frequencies" function! Some U.S. receivers do support using the "PTY" function to find some other station airing the same *type* of programming though not necessarily the same program. But RDS itself is relatively rare in the U.S.. -- Doug Smith W9WI Pleasant View (Nashville), TN EM66 http://www.w9wi.com [0] Four stations in Windsor, Ontario, Canada have requested government permission to use both Eureka *and* IBOC. Windsor is located just across a river from Detroit, USA and stations there cannot be economically competitive without reaching a large audience in the U.S.. Unfortunately DAB is seeing little financial success in Canada. [1] It is already possible via satellite radio. There are two services - XM and Sirius - which provide nationwide coverage via satellite direct to cars/homes. Both recently obtained permission to install low-powered terrestrial repeater stations to ensure reliable coverage in central city areas where tall buildings sometimes shield listeners from the satellites. |
"Doug Smith W9WI" wrote in message ... For that reason, while I've logged over 1,200 FM stations here, I've *never* seen one using the RDS "alternate frequencies" function! Surely you've heard West Virginia Public Radio stations - call letters generally WVxx. As of a few years ago they all had the AF function active. I'll admit I haven't checked recently. WETA-FM/WETH-FM had AF some years ago, but they turned off their RDS a couple of years ago. [1] It is already possible via satellite radio. There are two services - XM and Sirius - which provide nationwide coverage via satellite direct to cars/homes. Both recently obtained permission to install low-powered terrestrial repeater stations to ensure reliable coverage in central city areas where tall buildings sometimes shield listeners from the satellites. Both sat system have had terrestrial repeater since Day One. They have a continual fight to continue operating them. IIRC, the recent action merely extended temporary operating permission. AM/FM broadcasters fear the satcasters and are playing whatever game they can to restrict their operation. I had a 2.5-hour tour of XM this Monday. Billions of dollars invested. They have around 800 terrestrial repeaters. My guess is that they have 60 to 75 percent of the number of subscribers needed to break even. One meaningless statistic: they had 25,000 subscriber activations Christmas Day 2003. |
R J Carpenter wrote:
Surely you've heard West Virginia Public Radio stations - call letters I have heard the Charleston outlet, but only once and before I had a RDS decoder. Reception to the east is pretty difficult from here - I've never heard South Carolina and have only one each N.C. and Virginia station in the log. -- Doug Smith W9WI Pleasant View (Nashville), TN EM66 http://www.w9wi.com |
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