New Audio Head Units are not optimized for Power Antennas

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  1. #1
    CelicaSupra.com Member supraz's Avatar
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    New Audio Head Units are not optimized for Power Antennas

    I have finally bowed to the inevitable and have purchased a Sony XAV-AX1000 Double DIN head unit with Bluetooth phone capability.
    While generally pleased with the unit, while installing it I have found that the system doesn't work very well with the Celica Supra power antenna.
    Because the head unit is capable of Bluetooth and voice response, the unit stays powered up even if you are not using the Tuner function, or any other music function for that matter.

    This means that as soon as I put the car ignition switch to either Accessory on Run positions, up comes the antenna even if I am not planning on using the radio. This isn't the end of the world, but there are times when I want the darned thing down!

    Older stereos had two wiring harness functions that made this work.
    Amp Remote: Blue/White Colour wire - Sends a 12V signal to turn on an external amplifier
    Antenna Remote: Blue Colour wire - Sends a 12V signal to turn on a power antenna. This is is what used to control my antenna in my 1992 vintage Sony.

    Now, Sony and other major vendors seem to have combined these functions into 1 signal that has various names. But because these have to power external amplifiers (like I have,) as soon as the ignition switch is turned on it has to be available to play voice commands. As a result, up pops your antenna as soon as you turn on.

    I guess it's a sign of the times. Most new cars don't have power antennas so why have a feature for them?

    I'm now messing around to add a manual switch to allow me to manually raise or lower the antenna. But damn it, I have to mount the stupid thing and probably modify my 36-year-old interior plastic!!!

    Moral of the story is to check the Installation Instructions of any new head unit before you buy it to see if this is an issue for you.

    Dale
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  3. #2
    CelicaSupra.com Member MrBubbles00482's Avatar
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    Yeah, its a common issue now a days. Most manufactures have dropped the antenna remote and just give you an amp turn on output....or they are stupid like Kenwood and leave the wire in the harness and it doesn't do anything. Being in the car audio industry for the past 14 years I've seen them dwindle down.

    That and 90% of radios don't have TRUE preamp RCA outputs. Just a glorified line output converter built in.
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  4. #3
    Boosting Mod SilverMk2's Avatar
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    I just unplugged the power antenna. I haven't listened to fm radio in ages now.

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  6. #4
    CelicaSupra.com Member supraz's Avatar
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    Quote Originally Posted by SilverMk2 View Post
    I just unplugged the power antenna. I haven't listened to fm radio in ages now.
    Very true. Although occasionally I like to get the traffic radio for local updates. It can be a hassle to do it online when you're driving.

    AND I like to pop the antenna up. Lots of young kids have never seen a power antenna and are amazed and amused by it. It's part of the charm of an '80s car!
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  7. #5
    CelicaSupra.com Member supraz's Avatar
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    Quote Originally Posted by MrBubbles00482 View Post
    That and 90% of radios don't have TRUE preamp RCA outputs. Just a glorified line output converter built in.
    Do tell more! What is a line output converter? What are the ramifications of this?
    This is the sort of thing that you don't typically hear about.

    In the "olden days" the preamp output was a low level signal (in the mV range iirc) from the signal source (cassette, CD, tuner, that was the same signal fed INTO the amplifier stage of the head unit.
    Are you saying that nowadays the signal is amplified to high voltage/current by the integrated amplifier and then is REDUCED back down to a level suitable for input to an external amplifier?
    From what I can see, the integrated amplifiers in most audio head units are not particularly high quality.

    I'd like to hear more about this.

    Dale
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  8. #6
    CelicaSupra.com Member gamble's Avatar
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    Put the antenna on a clapper
    :clap on:
    antenna goes up
    :clap off:
    antenna goes down
    :P
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  9. #7
    CelicaSupra.com Member SupraFiend's Avatar
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    Good lord, don't modify the interior plastics. Just get another fog light switch and put it in one of the blank spots in the center console (or toss your coin holder if that's whats filling your blank spot).

    Is this for the black or white one?

    I hate power antennas, they are so unreliable. At least the oem one was. My car had about 215,000 kms on it when I got it, and full history since new from the original owner (I'm 2nd). The guy replaced the mast 3 or 4 times and the entire unit 2x. He spent well over $1000 at toyota keeping that thing working from 1986 to 2001.
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  10. #8
    CelicaSupra.com Member Funkycheeze's Avatar
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    I usually install a small rocker switch inside the 'cubby' that ends up being installed above/below the radio for most dash kits of cars that come with a double DIN stock radio (like ours). The rocker controls if the antenna is up or down, I find with my MR2 Spyder, I only need to extend it when I am out of the city. Or just go to the windshield antenna!
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  11. #9
    CelicaSupra.com Member Zerodrag's Avatar
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    Yup... for those headunits that have that antenna issue, I just place a two-position toggle/rocker switch intercepted into the antenna wire. Easiest solution.

  12. #10
    CelicaSupra.com Member
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    It's true that most modern units don't have true line level preamp outputs anymore. But that's not necessarily a bad thing. In the old days, line level was only really a "standard" in home stereo stuff at 1V peak to peak output which generally changed when CD players were introduced with 2V P-P outputs.
    "Line level" in car stereo stuff generally followed the home standard, but some manufacturers used whatever they wanted. Older Kenwood stuff was about 200mV P-P and some high end brands were as low as 30mV P-P. This was all fine as long as your system was all one brand, but problematic when mixing brands. On the Kenwood's, I used to modify the line level by swapping some resistors in their preamp outputs to bring the level up to the normal 1V P-P. In more extreme cases, I would build a small adjustable gain stage into a plastic film can (remember those!) that could easily be powered from the amp turn on lead that had a level control on the cover.
    In the really old days when booster / equalizers were the awful norm. Nearly all of them simply were a low gain / high noise stage that simply amplified the normal speaker output level and its noise. Yech!!!! But there were a few that more or less buffered the speaker outputs by using some sort of higher impedance input stage or an input transformer that greatly reduced the output current and noise in the head unit. These sounded much, much better than the others. (CarFi)
    But it wasn't long before high end companies got involved and soon there was a true 25 W RMS amp without a switching power supply. (Audio Mobile) The only real problem was that the components all had to be precisely matched or noise and distortion rose considerably. Then switching power supplies came into the picture and real output grew to incredible levels.
    However, the car has always been a noisy environment and higher preamp levels reduce the apparent system noise level. So it's not uncommon these days for line level preamp outputs to be 4, 6, even 8V P-P. This allows the input gain on the amps to be reduced accordingly which lowers noise. And many of these units have built in MOSFET amps which are incredibly clean so using a "glorified" line output converter with them isn't a problem.
    And yeah, power antennas are almost nonexistent these days. One of the worst examples was our original OEM units. Some Toyota engineer thought that it made sense to stop the antenna briefly while in start mode to save wear and tear on the antenna. Virtually every other unit ever made would briefly reverse direction while in start mode then reverse again and continue up after the engine was running. Yeah it was cool that the antenna wasn't raised except for radio mode. But many other OEM and aftermarket units used to work like this as well.
    Then there was a while that many OEM head units had some really cool features that were exceedingly rare in the aftermarket. One was FM front ends that adjusted the length of the antenna to the frequency being tuned instead of having to compensate for everything in the FM section. So the proper 1/4 wavelength at 88MHz was 31" and at 108MHz was 28" and these units adjusted the length to the tuned frequency instead of compensating for everything being optimized for 98MHz. There's still some OEM head units that use diversity tuning to pick the best signal from 2 different antennas. Almost always, the second antenna is the rear defroster grid. Sure the antenna is isolated from the defroster but having 2 antenna inputs to choose from (actually 2 separate FM front ends) that just happen to be about the right distance apart so that one nearly always has a good signal works extremely well. But even this isn't really necessary anymore with HD radio.

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