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Early semi-auto antenna question

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

  1. DGS

    DGS Four 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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  3. DGS

    DGS Four Time F1 World Champ
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    #27 DGS, Dec 18, 2003
    Last edited by a moderator: Sep 7, 2017
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  4. DGS

    DGS Four 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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  5. Cenzzo

    Cenzzo Rookie

    Nov 5, 2003
    11
    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
     
  6. joeyy

    joeyy Karting

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    #30 joeyy, Dec 18, 2003
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  8. joeyy

    joeyy Karting

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    #31 joeyy, Dec 18, 2003
    Last edited by a moderator: Sep 7, 2017
    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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  9. joeyy

    joeyy Karting

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    #32 joeyy, Dec 18, 2003
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  10. DGS

    DGS Four 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.
     
  11. Wayne 962

    Wayne 962 Formula Junior
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  13. robertgarven

    robertgarven F1 Veteran
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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
     
  14. robertgarven

    robertgarven F1 Veteran
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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?
     
  15. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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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.
     
  16. 308 GTB

    308 GTB F1 World Champ
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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
     
  17. 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 ;-)
     
  18. Difaz

    Difaz Karting

    Mar 30, 2005
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    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
     
  19. 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!
     
  20. TonyMorristown

    Jul 14, 2018
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    Tony Dwones
    @dave80gtsi Thanks a bunch! This Diode solution was dead easy and is a snap to install. I replaced the Hirschmann 8600S "semi automatic" antenna in my '81 308 GTSi over the weekend. I put in a Hirschmann HIT AUTA 2050 (~$90) which is the more modern "fully automatic" style. I was about to install the Diode in the console switch, then realized it can be anywhere in the circuit. So I put it in the trunk. It sort of "jumpers" between the two main connections on the fully-automatic antenna. I used a 3 amp diode because I had it handy. In theory, you should use a 5A because that's what the fuse is set at. Don't forget to also connect the Ground wire on the fully-automatic antenna so it can complete the circuit. This was by far the easiest way to put in a new antenna. The Hirschmann 2050 fits in the same space as the 8600S did.
     
  21. dave80gtsi

    dave80gtsi Formula 3
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    Holy thread revival, Batman!

    I posted that blurb back in 2003, and it is still of use to someone today!

    Can't ask for more than that!
     
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  22. TonyMorristown

    Jul 14, 2018
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    Haha Dave. Good advice is always good advice. I imagine that as time goes on, all the old power antennas will need to be replaced.

    PS. With 17 yrs of experience, did you ever go for a fully automatic antenna with signal from the radio? Or are you still running the antenna “semiautomatically“?
     
  23. dave80gtsi

    dave80gtsi Formula 3
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    To be honest, the whole question is somewhat moot for me, as I almost never turn the radio on.

    But it did bother me that the console switch did not operate as the factory intended when I bought the car way back then - thus the diode usage. And now, 17 years on, those diode's are still perking right along!
     
  24. jsumnertx

    jsumnertx Karting
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    Dec 9, 2004
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    Austin
    For those of you who watch this thread and haven't seen my antenna ground strap problem, c'mon over for the fun :)

    Trying to fit one of these
    Spec-D Tuning ANT-105A 12V Power Am Fm Radio Antenna Mast Replacement Kit, Wiring, Cable

    into my North American 1979 308 GTS. I haven't had a power antenna since I got the car 22 years ago.

    The car came this way:
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    With this wiring harness (and the little ground strap unconnected)
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    I've done the diode mod on the antenna (using the 3 diode system)

    Now after having the antenna work when I manually give it power from the battery but not working when connected to the harness, I currently suspect a bad ground

    https://www.ferrarichat.com/forum/threads/bad-power-antenna-ground.632142/
     

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