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Early semi-auto antenna question

Discussion in 'Technical Q&A' started by robertgarven, Dec 15, 2003.

  1. DGS

    DGS Three Time F1 World Champ
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    #26 DGS, Dec 18, 2003
    Last edited by a moderator: Sep 7, 2017
    The diode solution is for a fully automatic antenna -- the kind that automatically raises when the radio is switched on. The fully auto antennae have a control box internal, and three leads, as described above. Normally, these antennae only remain raised while receiving a radio signal from the stereo. They then retract using the constant battery power. The diode solution removes the retract power unless the switch supplies it.

    Based on the antenna switch, the original antenna must have had a double wound motor with a separate ground. Apply power to one winding, and the antenna raises. Apply power to the other, and the antenna lowers. Remove power, and the antenna stays where it is.

    If you have a semi-auto antenna with a single winding, you have to apply power to one lead and ground to the other to raise it. Reverse the leads to lower. To make this work with the original SPDT/center off switch, you need the relays.

    In the attached figure, the top schematic is for a double wound antenna motor. The lower schematic shows a relay solution, beside a connection drawing using standard Bosch relays.

    The second drawing shows a schematic for the diode solution with a fully auto antenna.
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  2. DGS

    DGS Three Time F1 World Champ
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    #27 DGS, Dec 18, 2003
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  3. DGS

    DGS Three Time F1 World Champ
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    #28 DGS, Dec 18, 2003
    Last edited by a moderator: Sep 7, 2017
    Here's perhaps a cleaner relay solution for the semi-auto ants, using a Radio Shack DPDT relay (cat# 275-218 (socket 275-220)).

    The "down" side of the switch applies down power through the normal contacts of the relay. The up side of the switch causes the relay to switch, reversing the ground on the motor, and supplying up power.
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  4. Cenzzo

    Cenzzo Rookie

    Nov 5, 2003
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    Hi there,
    I would love to be able to just tie my antenna in to the radio lead for it so that it automatically goes up or down when I turn the radio on or off. Fumbling with that console switch to make it go up and down is going to get me in a car accident one of these days!
    Does the fix you talk about allow for this to happen? If so, I'd be interested in specifics for sure. My email is cenzo@go.com, or fax is 650-345-3079, or I'm open to how else to exchange the info.
    Thanks in advance,
    Vince
     
  5. joeyy

    joeyy Karting

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    #30 joeyy, Dec 18, 2003
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  6. joeyy

    joeyy Karting

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    #31 joeyy, Dec 18, 2003
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    inside of antenna. notice the extra set of windings that connect to the motor. this is what i believe changes the polarity because one side is up and the other is down. also the motor is grounded at the antenna body not at the switch.
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  7. joeyy

    joeyy Karting

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    #32 joeyy, Dec 18, 2003
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  8. DGS

    DGS Three Time F1 World Champ
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    These techniques are to retain the original function.

    For a fully auto antenna, you'd have to route new wires from the radio to the antenna -- and you'd need a new fully auto antenna. Full auto ants have switches to detect max extend/retract positions. Trying to adapt a semi-auto antenna to fully auto would take a control sequencer and a current sensor to detect when the antenna can't move any further.
     
  9. Wayne 962

    Wayne 962 Formula Junior

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  10. robertgarven

    robertgarven F1 Rookie
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    Thanks Wayne,

    I think the angle makes the car look nicer, as with all ferraris most have a good side and a well not bad side but one less flattering. I got the QV wheels from dave h. in this post. Although not correct on a 75 car the QV wheels were an option in Europe in the 79 gt4 spare parts manual making them not entirely in correct in my warped way of thinking. I am tryng to deide what to do about the antenna still, thinking a course in basic electronics is in order! :)

    Rob
     
  11. robertgarven

    robertgarven F1 Rookie
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    I noticed Ferrari UK has a switch available that superceeds my switch I wonder if I bought it and could ground it whether this would solve my problem?
     
  12. f355spider

    f355spider F1 World Champ
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    Rob,
    I would ask Jeff and Mark what the difference is in the switch. My understanding is that the originals are no longer available and this may be some sort of "replacement". But ask to be sure. In other words, it may not have anything particularly different (electrically) with it.
     
  13. 308 GTB

    308 GTB F1 Veteran
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    Here's a good solution for those with a functional original AUTOVOX semiautomatic antenna experiencing a break in the nylon cable.

    The Carquest semiautomatic antenna (part# 81050) has a similar cable drive to that of the AUTOVOX unit, utilizing a smooth rather than a thin geared cable. The Carquest antenna mast extends to the same height as the AUTOVOX mast. The nylon cable is slightly thinner (2.7 mm in diameter vs 3.2 mm for the AUTOVOX) and the mast is a bit thinner as well (8.2 mm vs 1.0 cm) and is made of stainless steel rather than chrome. The solid top section of both masts are identical and are stainless steel. The tips can be unscrewed fom both top sections and are interchangeable as the threading is identical.

    Simply harvest the top mast section with attached nylon cable from the Carquest unit and replace the corresponding AUTOVOX top mast section with attached broken cable. You can modify the clip on the end of the Carquest nylon cable to secure it to the spool of the AUTOVOX unit with the original cotter pin. Clean and lubricate the AUTOVOX assembly well as long as you have it apart,

    This repair allows you to maintain originality, if that's important to you, and keep the semiautomatic AUTOVOX unit, original wiring, and the exterior trim pieces. The original AUTOVOX power antenna is strong and very well built. The slightly narrower nylon cable might even be an improvement as it will be less likely to bind if you don't occasionally clean and lubricate the assembly.

    Here's a picture of the AUTOVOX mast (with broken cable) and the Carquest mast.

    Barry
     
  14. stlouis

    stlouis Karting

    Oct 7, 2007
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    Guys, wanted to share with you : on my 308GT4 1979, I changed the broken and non-OEM antenna with the semi-auto Autovox 86 which is supposed to be the original model, and ... it just works fine.

    Found it on eBay.it : the autoradio guy did not speak a word of English, but Google translate proved to be good enough ;-)
     
  15. Difaz

    Difaz Karting

    Mar 30, 2005
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    Phill
    I have a fully automatic antenna in my 308 GTB and got it to work with the standard OE switch by wiring in the diode as suggested above.
    The only thing I did differently is instead of placing the diode at the switch I placed it at the antenna across the wires A and B.
    This way all of the wiring belonging to the car is original. Only the antennas own wires are modified.
    Thanks for the info. Easy mod and works perfectly.

    Difaz
     
  16. Jeff Cowan

    Jeff Cowan Rookie

    Feb 21, 2018
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    I think there is a typo in the above. When I wired it this way the up action worked but not the down. Then I thought about it and flipped the wires so that B wire attaches to Up side and A wire attaches to Down side with the diode running Up-to-Down direction. Now activating Up sends current across B, through the diode to A and completes the circuit. Down sends current to A and the diode blocks current going to B making the antenna think the radio has been switched off. Voila! I also put the diode across the new antenna wires so the car's wiring remains original. Hope that helps!
     

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