car stereo

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wrote:

long wire aerial or any aerial that happens to be on the roof or in the loft?
Rudge
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wrote:

No,Saturns have plastic panels over a steel chassis. Mostly on the sides,I believe the roof is still steel.

--
Jim Yanik
jyanik
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Car stereo works just fine in my fiberglass sailboat. The "antenna" is just a long antenna cable extension with the shielding stripped off of the last 31 inches. It's tucked up inside the headliner inside the cabin.
CWM
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Well, I remember who gave me the ground plane story. It was a friend who works in an ancillary part of communications. Don't know where he got his information, but he could very well have been wrong.
He even offered me a ready-made box that sounded like it was designed to hold a car radio and power supply. He's been trying to clean up so I hope he still has it.
If I had done this earlier it might have been good, convenient and saved me time. Otoh, it's not like I've suffered so bad these past years. One GE AM-FM clock radio from 1972, in my office, gets one of the 2 DC stations well enough all the time, and the other station about welll enough almost a half of the time. It will work for weeks and then not work for weeks. I think they change things at the transmitting station in DC. WAMU. It's this radio I guess that is motivating me to find a better replacment.
The radio in the bedroom gets both, and both well, though lately it has't been getting the local Baltiomre station WYPR so well. That was perfect for 15 or 20 years! Maybe they changed the transmitter too.
The current very cheap looking Admiral clock radio from tthe 1960's or 70's gets both, although WAMU not perfectly.
Plus I keep a radio outside in the summer time. I think it got both stations but I haven't listened yet and I forget how well.
But these are the best of about 20 radios I've bought at yard sales, plus two fairly expensive stereo tuners, which don't get WAMU at all.
Thanks to everyone. Maybe I'll be able to give some follow-up some day.

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He's right. The best place for a car aerial is on the (steel) roof where it acts as a ground plane, as well as being as high as practicable. However, field strengths are designed for much less efficient aerials - in urban centres at least. So car designers will go for a 'prettier' look - hence the appalling devices built in to rear screens etc which quite simply don't perform as well in poor signal areas. But the other snag is it's not really possible to use the correct length for AM reception as it would be too long in practice.
Ideally, the aerial should be as far away from sources of interference as possible - and in a petrol car this means the engine. But the downlead should be kept as short as possible too which is somewhat of a dichotomy. IMHO, the best compromise is at the rear of the roof, with a head amp to make up for losses caused by the longer lead. In an ideal world you'd also use separate feeder cables for VHF and MF.
--
*Is there another word for synonym?

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Sat, 19 May 2007 09:51:14 +0100, "Dave Plowman (News)"

Thanks for replying. It's not reception in the car that is a problem. It's getting the same reception in the house.
So that's the thing. The stations I wanted were in DC about 45 miles from my house, so the field strength is not high here. So my friend was saying even the less efficient mounting place for the aerial, on the side of the metal fender, would be a better place than in the house, where it would have had no "fender" at all. The first floor of my house and the parking lot are the same height. So, that the car radio worked in the car wouldn't mean the same radio would work in the house.
So -- unless I ran an aerial to the attic or the roof, which I didn't plan to do when I talked to him -- maybe he was right that the car radio woudln't have worked on the first floor??

I don't think there is much interference in my wood frame house, with a few electrical outlets, and a few ceiling fixtures, all of which could be turned off if it helped, and one aluminum-frame window. Plus two steel I-beams that hold up the second floor. But maybe these things have more effect than I realize.
I'm judging by noting the effect that various steel bridges have on reception when I drive through them, and a bridge that has no more steel than my house's second floor doesn't have much effect if any.
I'm also judging the FM part by the fact that some radios do receive the FM stations I want in the house. I had thought the car radio was BETTER than any of them, but if it is the not as good as it could be but still a lot better than no ground plane that exists when mounted at the car fender, and not the radio, at least my friend will have been right. Which is important in itself to know, even if there were ways around this by mounting an aerial in the attic.
I couldn't find a single AM radio that would get WRC Washington DC in the house, even when I was on the second floor, even though it came in clearly in the car. My friend said that the car radio wouldn't work as well in the house as it did in the car, even with the aerial mounted on the side fender of the car.

If you are inclined to email me for some reason, remove NOPSAM :-)
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Talk about using a sledgehammer to crack nut. What an unnecessary lot of work. And almost certainly inferior to a domestic hi fi.... Just get a decent hi-fi tuner and a good external aerial (maybe some kind of amplifier would be useful if the reception is no good). Your signal depends to a large extent on the quality of the aerial so don't skimp on it.
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The main problem with plastic bodied cars is interference from the car ignition, etc. On others the engine is in a sort of Faraday cage. Hence the earthing straps you often see across the bonnet (hood) hinges. Although this is mainly for the benefit of others to prevent RFI to TVs etc. But it helps the car radio too.
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*Where do forest rangers go to "get away from it all?"

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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London SW

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On Fri, 18 May 2007 09:58:25 -0700, "charlie"

Corvettes have a layer of wire screen embedded in many body panels, including the hood.
CWM
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London SW

have you seen the engine compartment of one? my 94 certainly doesn't have a bottom panel under the engine, nor side panels where the wheels are. there are no bonding straps over the hinges, which are on top of the front bumper anyway. it doesn't have a front panel in front of radiator, just the bumper, which does not have wire mesh, nor any mesh behind it. how much of a faraday cage would it be with only the hood having wire screen, if there was actually one there, and which isn't bonded to anything?
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On Fri, 18 May 2007 10:14:44 -0700, "charlie"

You are incorrect in many of your observations and conclusions. If your hood and other body panels did not have a grounded screen embedded, Your radio would be entirely useless, especially on the A.M. band. All you would hear is ignition noise, and probably your horn, heater motor, and wipers, through the speakers. The fact that there are some openings is of no consequence.
CWM
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wrote:

The 69 Corvvette I had was ordered without a radio and it was missing the radio kit. That was shielding on the plug wires and distributor. I even got noise in my 8 track player. An AM radio was useless
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A Faraday cage can be made of mesh. Doesn't have to be solid steel.

Some sort of, yes. But it's still better to stop interference getting to the aerial - especially for distant reception.

I didn't say it wouldn't 'work' Only that it won't work as well as in a metal bodied car unless some form of alternative screening is used.
--
*If horrific means to make horrible, does terrific mean to make terrible?

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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This is a good idea, and not hard to do. Car radios have an edge over most table-top radios since they always incorporate RF amplifiers to boost weak-signal conditions, and pack a lot of power for the small size they take up. And very cheap, if picked up at a yard sale.
What you needis to understand which terminals on the radio itself are for +/- 12 volts, Right +/- speaker and Left+/- speaker leads. Low voltage so not a fire hazzard. Sound will be as good as you'd want if you've found a reasonable radio and good speakers.
The ground-plane theory sounds reasonable until one realizes that the antenna length and car's metal chassis size are nowhere near the right dimensions needed for resembling an AM ground plane.

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Not always as safe as you'd like. I've had a car radio set the dashboard on fire when the alternator was screwed up and spiking higher than the noise-suppression coil could cope with.
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In a pinch, I've been able to arc weld steel using a 12 volt car battery for power.
CWM
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