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    Pregunta's Avatar
    Pregunta Posts: 169, Reputation: 3
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    #1

    Jul 30, 2008, 06:23 PM
    Auto Radios better Reception
    Why do some brands of automobile radio provide much better reception than others?
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #2

    Jul 30, 2008, 06:53 PM
    Cost and quality of the design.

    In the 70's I bought an FM only analog tuner for a home stereo system which listed for $460. I've seen that tuner get 3 different stations clear just by rotating the antennae. It also had two different Intermediate Frequency bandwidths. One would give a higher quality sound, while the other would tend to reject interference from other stations.

    The inermediate frequency of usually 10.7 MHz is the frequency in which all the decoding is done with FM at within the radio. The local oscillator which is 10.7 MHz above the frequency of interest within the radio has to be stable as well. The hetrodyning process creates a sum and difference frequency. The difference being 10.7 MHz. The sum signal has to be rejected.

    You can probably pick up an AM/FM radio for less than $20.

    Big difference, right?

    For car's, diversity reception can make FM a lot better. This system uses 2 antennaes and two tuners and the best one is selected. One of the antenna's is the rear window defogger. The other is the antenna in the front windshield. The lack of this system is apparent when your stopped at a traffic light and the signal gets real bad and then you move a few feet and it gets better.

    FM stations are either horizontally or vertically polorized meaning they are best received with an antenna in the same direction of the polarization. Most FM stations are Horizontally polorized, but the windshield antenna section for FM is vertically polorized.

    FM is very susceptable to "multipath interference" where signals hit the antenna delayed after bouncing off other objects. The way FM is encoded makes Stereo hard to decode without hiss unless the signal is strong. Some radios vary the blend, others just abrubtly switch to mono.

    FM signals are also very directional.

    As a kid, I made an AM radio using a couple of parts. A cat whisker for tuning and a diode and a single transistor amplifier. That won't cut it in the real world, but it shows just how cheap you can go.
    kitch428's Avatar
    kitch428 Posts: 1,434, Reputation: 152
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    #3

    Jul 30, 2008, 08:45 PM
    Very good reading. I made an AM from a Heathkit. Remember those? What was Radio Shack before it became Radio shack? Realistic? I can't remember. But the kit came from there.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #4

    Jul 30, 2008, 09:19 PM
    It was always Radio Shack. They used to have catalogs about 1/4" thick. Their brand was Realistic. Allied's brand was Knight Kit. Lafayette Electronics was Lafyette. Then there was Eico and Heathkit.

    Then there was Short-wave radio and the Voice of America Breakfast Show late in the evening. And don't forget tubes and mechanical oscilators (about 200 Hz) called vibrators. Car radios were tubes, now called valves by audio purists.

    I had a Blaupunkt (Blue dot) tube radio which was AM/FM/SW. The dial was in wavelenght instead of frequency. I built a solid state vibrator for it.
    kitch428's Avatar
    kitch428 Posts: 1,434, Reputation: 152
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    #5

    Jul 31, 2008, 03:14 PM
    Neat stuff! Going back further... I sold a TV on the internet when the internet was young. Before Ebay. It was a reconditioned Dumont, walnut cabinet, with FM radio!! Vintage 1949. Now that was ahead of it's time!
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #6

    Jul 31, 2008, 04:29 PM
    Got two TV's here at home with a Channel #1 on them. One is an RCA, and the other a Philco with a evidently bolted on contraption of it's day, a blue bubble magnifier, to make the picture bigger. Looks like a TV wearing a space suit.

    How about a "tube portable radio" complete with a handle. Probably 8.5" x 11" x 3". That's around somewhere.

    A TV with an FM radio. I "may" have briefly remembered one of them my father had. Orange dial?
    kitch428's Avatar
    kitch428 Posts: 1,434, Reputation: 152
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    #7

    Jul 31, 2008, 06:58 PM
    Yes, an orange dial with a sweeping needle that went around in a semi circle. The box was about 2-1/2 sq ft. Picture tube was about 13" at the widest point, and it weighed 90lbs.

    My father referb'd it and gave it to me. He's a retired electrician and started out as a radio and tv repairman. And because of him, I do remember the portable tube radio.
    My days as a kid were around the time you could still find a tube tester in the drug stores, but hardly needed anymore due to transistor radios and TV sets coming in strong.

    Our first color TV was around '69. it was a Quasar with "the works in a drawer".
    Pop was fastinated by it and had to see what made things tick. Brand new set and he's got the guts of it all hanging out. (I'm LOL thinking of this as I write) hehehehehe
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #8

    Aug 1, 2008, 11:13 AM
    Jeesh:

    We are similar. My father got an apprentice job as an electrician and lost it because of an accident with a vehicle. He then worked at a factory, but he repaired TV's and radios for his co-workers. Transistors caused him major headaches.

    Yep, tube testers all over when I was a kid too.

    First color TV the family has was in 1968. Basically purchased very few TV's. Used other people's garbage and fixed them. There are lots of them in the house. I count 8 working TV's. 3 are used heavily. None digital. Not cable. I see a problem soon.

    Anything that was broke, I had to take it apart first and TRY to fix it.

    There is a VCR and Monitor which is counted as a TV which is used for recording and playback throughout the house.

    I didn't count a Slingbox which allows my Laptop to become a TV.

    That's the simple version.

    I see you like Toyota's too. Me as well. I Maintained one. Got 237K miles and 17 years out of it.

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