"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