Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?

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In alt.home.repair, on Fri, 23 Jul 2021 12:30:09 -0400, Clare Snyder

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Actually, it's that car radios have always given me better reception
than house radios have.   Is it the antenna, the ground plane?  What?  




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Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On 7/23/2021 8:47 PM, micky wrote:
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Typically better reception in the car, yes, but that all depends on the  
antenna set up.  You can have a very good antenna at home, but one with  
a fault in a car.  I've owned both.  I'd like to build an AM loop in my  
attic to get better AM reception at some point.

I am very into AM radio, especially long-distance AM stations at night.  
  I've owned cars where they seem to put no thought into the AM radio  
band, and it shows (sounds).  Dad had a Chevy Trailblazer (2006?) where  
you could always hear the transmission or something interfering with the  
AM reception.

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
In alt.home.repair, on Sat, 24 Jul 2021 00:13:18 -0400, Michael Trew

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Wow.  

The '72 Buick and then the '84 Chrysler and 88 Chrysler would get
perfectly here in Baltimore WRC, 980AM, in Washington, DC, a station no
indoor radio, even the fancy receiver, would get at all.  (I've only
lost interest in that station because it changed format.)  

And for decades, one car radio after another, (maybe the Buick,) Chryler
and Toyota, would get WAMU, 88.5FM, (American University in DC),
perfectly, when only one inside radio would get it.   Even now a much
different Toyota radio gets WAMU usually perfectly, when the one inside
radio no longer does as well. (For a while I was reporting to the WAMU
engineer when reception was good or bad, and he got it good, but months
later, it got weak again sometimes. (And like I say, that's the one
radio that gets it at all.)  

At one point a friend gave me a nice wood "box" designed to hold a car
radio, an antenna, and a DC adapter, just for the sake of using a car
radio indoors, but at the same time he told me that it didnt' work for
him (which is why he was giving it to me).   So it seems like the
difference is the metal body on cars, all but a few cars.  

The urls people have posted here (before electronics.repair was added)
make clear that the ground plane in the car makes a difference, and that
cars without one need a special antenna cable, but a) they're mostly
pushed for CB radios, b) it's not at all clear that the special antenna
is as good c) when shopping for an antenna, any with ground plane
provision probably make note of it, but those without do not, afaik,
warn people what is missing.  

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
@fmguy.com says...
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One other thing about the radio in the house is that some homes have so  
much metal in them , especially the aluminum siding and foil reflecting  
insulation that the radio signals have a hard time getting in to the  
house.

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
In alt.home.repair, on Sat, 24 Jul 2021 10:21:07 -0400, Ralph Mowery

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I have T1-11 siding, not alumininum   As to foil clad insulation, I
don't think so.  I've been in the walls a little bit when I put a
floodlight in the outside bedroom wall.   House built in '79, not cheap
but not the most expensive either.   Plus there is a 6-foot wide window
facing DC from the bedroom, where many of the radios have been, with
aluminum window frames but the frames are not very big.  

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On Saturday, July 24, 2021 at 10:21:11 AM UTC-4, Ralph Mowery wrote:
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That's odd.  If you go to the NASA space museums, you see that the early 1970's satellites have all of this gold and copper looking foil around the satellite's lower regions.  I thought that helped with transceiver communications.

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
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Heat.

Peter Wieck
Melrose Park, PA  

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On Sat, 24 Jul 2021 16:10:41 -0700 (PDT), "Peter W."

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True, but with one notable exception.  The original space suits were
ugly green pressure suit affairs, that looked awful in press photos
and videos.  So, NASA hired fashion designers Rudi Gernreich and later
Pierre Cardin to design something futuristic and more in line with

<https://static1.squarespace.com/static/57c4ce9d1b631b5c58eb6a71/t/589686ed20099e1b6fb66664/1486259962410/Spacesuit+pamphlet.pdf


--  
Jeff Liebermann                 snipped-for-privacy@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
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Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
@fmguy.com says...
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For AM radios in cars, the ground plane effect is almost nill.  There is  
some capacitance coupling from the frame to the gound, but that plays  
very little in the AM band.  The FM antennas are often built in the  
windshelds and the metal of the car does not com into play there either  
to ammount to anything.

To be much of a ground plane at the AM band you would need a plate of  
around 100 feet, 200 feet would be better.  Just look at how tall the AM  
transmitter antennas are.  Those antennas have about 120 wires as long  
as the antenna is tall burried in the ground.


Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On 7/24/2021 10:26 AM, Ralph Mowery wrote:
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This is the big difference in spectra that I looked at:

https://courses.lumenlearning.com/boundless-physics/chapter/the-electromagnetic-spectrum/


Shorter wavelengths penetrate better.

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
In alt.home.repair, on Sat, 24 Jul 2021 10:26:38 -0400, Ralph Mowery

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Only one car had the antenna in the windshield.   A long time ago, I
can't remember which.  
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So what can I do to get reception inside as good as what I get in the
car?   Especially FM.  In the past year, reception for WAMU, 88.5 and
C-Span, 90.1, seems to have gone downhill.  

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
@fmguy.com says...
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For in the house put up an outside antenna and feed it with coax cable.



Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On 7/24/2021 11:16 AM, micky wrote:
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My 1986 Chevy C10 has a windshield antenna.  Then again, it has many  
parts from a 1976 also (including the VIN and title).  It's hard to say  
which year had that windshield; maybe both.

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?

On Sat, 24 Jul 2021 11:16:54 -0400, micky posted for all of us to digest...

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Could be because of Sunspot cycle 25

--  
Tekkie

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On 07/24/2021 08:26 AM, Ralph Mowery wrote:
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And for the best outcome, build in a swamp.


Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
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But that?s for the transmitter, it isn't the best way to do an AM receiver.  


Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
wrote:

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Done.  Locally, KSCO's antennas are located in Corcoran Lagoon (Santa
Cruz, California):
<
https://i.redd.it/d90te63rl5171.jpg

The excellent salt/brackish water grounding is responsible for KSCO's
very strong signal and large coverage area.
<http://ksco.com

--  
Jeff Liebermann                 snipped-for-privacy@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
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Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
wrote:

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I beg to differ.  Nobody seems to have mentioned the bane of all MF
(medium frequency) reception, RF noise.  A metal ground plane (car
body) does a tolerable job of isolating the AM antenna from the noise
generating ignition, black boxes, and gizmos.  With a plastic body,
the antenna will pickup more noise from the engine.

The typical car antenna is sometimes located as far away from the
noisy engine as possible and connected to the AM receiver with RG-62/u
93 ohm low-capacitance coaxial cable.  There is an adjustable
capacitor between the antenna and the receiver input capacitance to
resonate the antenna system.  The coax cable capacitance and the
receiver input capacitance act as a voltage divider.  The more coax
cable capacitance to ground, the less signal and noise arrive at the
receiver.  Choose your coax cable type and length carefully.

You can have a really sensitive AM receiver, and still not be able to
hear much.  The threshold of sensitivity is atmospheric and man-made
noise.
<https://en.wikipedia.org/wiki/Atmospheric_noise
Note the graph.  At 1MHz, the RF noise (mostly from thunderstorms) is
huge.  
<https://map.blitzortung.org/#3.91/39.62/-91.39
RF noise from neon signs, motors, sparking of any kind, etc just makes
it worse.  If you simply build a bigger antenna, or add an RF
amplifier, you increase both the desired signal and the noise
proportionally.  If a receiver and antenna produce some SNR (signal to
noise ratio), and I add more antenna gain, or more RF amplification,
the resultant SNR will be the same.  In other words, a bigger antenna
or a "signal booster" don't buy you anything.  The trick is to somehow
improve the SNR, which is not easy.  See various articles on the
PA0RDT mini-whip antenna for clues:
<https://www.google.com/search?q=pa0rdt+mini+whip

Car AM radios tend to have the minimum sensitivity and RF front end
gain needed to function in a strong signal environment.  They're not
made for digging signals out of the noise.  That's NOT because AM car
radios are made to be inexpensive.  It's because the receiver is
sitting next to a very noisy car engine.  Were it designed to be as
sensitive as an LF or HF receiver, all you would hear is engine noise.
Try it.  Build yourself a BCB (broadcast band) RF amplifier and attach
it to your car radio antenna input.  In most cases, you'll hear your
engine, pump motors, and atmospherics quite well, but the distant AM
stations will still be buried under the noise.

I don't have any suggestions to improve your mobile AM reception.
Well, maybe the obvious suggestion to do what you can to eliminate,
move, shield, or isolate sources of RF noise.  If weak AM signals
magically appear when you turn off the engine, the source of the noise
is obvious.  The problem is that you might do a wonderful job of noise
reduction on your car, such as buy a diesel, but that does nothing if
you're stuck in traffic and surrounded by other noisy vehicles. Notice
that the ultimate noise generator, the all electric car, usually does
not come with an AM radio.  For example, Tesla will sell you an
optional overpriced infotainment package that includes AM:
<https://electrek.co/2020/10/28/tesla-brings-back-radio-infotainment-retrofit/

Vendors used to sell rubber grounding straps, that discharge any
static buildup on the car body.  That should get rid of some noise.
However, I believe carbon doped car tires have largely eliminated the
need for those straps.

So, to answer your question, yes a plastic body gives lousy AM
reception if your engine belches lots of RF noise and your receiver is
reasonably sensitive.  If your receiver is stone deaf, it doesn't
matter.

Good luck.

--  
Jeff Liebermann                 snipped-for-privacy@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
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Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On 7/24/2021 10:06 AM, micky wrote:
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I have a '75 Dart on the road with a factory AM-only radio.  
Unfortunately, the fuse in the fusebox is good, but the radio does  
nothing when turned on.  It appears that all of the wires are in place,  
including to the one dash speaker, but the only think I can see it do  
when I turn it on is slightly dim the dome light when switched on -  
absolutely no audio.

I bet if it were working, being designed solely for AM transmission, it  
would pick up stations quite well.  It's solid state... I might have to  
tear into it at some point.  The preset station buttons still seem to  
work as intended.

Re: Do cars with plastic bodies, like the Saturn, give bad radio reception?
On 07/23/2021 10:13 PM, Michael Trew wrote:
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http://socalradiowaves.com/columns/am_antenna.html

I built a variation of this theme and it worked well. At the time I was  
living about 20 miles from the Mexican border and the highly directional  
nature of loop antennas let me null out the Mexican power houses.

This is a simpler version that doesn't require building a frame:

https://ccrane.com/How-To-Make-a-Simple-Powerful-AM-Loop-Antenna-For-Free/

http://earmark.net/gesr/loop/

That one is more technical. I didn't look through all the links but onr  
method was to use ribbon cable. When you solder the ends you offset the  
conductors and solder them to the one next to it so you're forming one  
long conductor.

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