HD Radio Mod: Power Antenna Trigger

**Iceman_jkh** · 12-20-2007, 10:05 PM

Hey All,

I modded my Visteon Hd Radio to automatically trigger my car's power antenna to extend when the radio turned on.

Before I show you how to do this, I gotta do a slight disclaimer:
The pin I used to carry the +12V for the trigger signal appears to have nothing else was connected to it (ie: it was floating and not GNDed or anything else that I could tell). I have tested it on/off for a couple of cycles and everything looks fine. No overheating, burning smell, etc. Hence I'm going to publish this. As always, perform this mod at your own risk! Dont blame me if something messes up.

Ok, so here it is.

-There are 2 relays inside the RF cage of the unit.
-We connect +12V (from the power supply connector) to the NO pin on the second relay ONLY.
-As far as I can see the NO pin (only on Relay 2) was always floating!
-Relay 1's NO pin likely goes to the iBiquity RF unit.
-After performing the mod use a male motorola plug header in ANT OUT to access the +12V line to trigger your power antenna.

NO = Normally Open (If the relay has no power this contact is NOT connected to C)
NC = Normally Close (If the relay has no power this contact IS connected to C)
C = Common

When you apply power to the relay's coil, the C contact will become connected to NO not NC.

Cheers,
Ice

**dmacias** · 03-15-2008, 03:13 PM

Thanks, this worked perfectly. I don't know if you explained it so well or no one has a power antenna.

**labenedict** · 06-19-2008, 10:41 PM

I'd like to also say thanks. I have it working in my setup now also.

**meisner** · 07-15-2008, 08:18 AM

So can the ANT OUT still be used for a regular head unit or is it only used to provide the +12v trigger to raise the antenna? It seems like no it can't.

If not, I suppose I can use the power that triggers the relay to raise the antenna...right?

**Iceman_jkh** · 07-15-2008, 08:52 AM

The ANT OUT provides only +12V. It does not provide any type of HD/FM RF signal pass-through.
Do not connect it to your ANT IN on your headunit/radio as it might damage it.
It is simply a +12V signal that is ON whenever the HD Radio is turned on by the PC. And OFF whenever the HD Radio is OFF. This way it can remote turn-on any device which only needs to be on/extended (antenna) whenever the radio is on.

**meisner** · 07-15-2008, 09:10 AM

OK, so my secondary assumption is what I should go with...I think.

I wonder if it'd be easier to find a splitter so I can split the RF signal from the antenna and do your mod so either device (CarPC or the headunit) can raise the antenna....or just tap the +12v that triggers the relay to raise the antenna. Then I can use the ANT IN/OUT ports as usual to feed the stock head unit.

**colin** · 07-15-2008, 11:50 AM

So wait, if the ANT OUT is never connected to anything when the radio is on, how does the RF modulation work?

**mitchjs** · 07-15-2008, 05:38 PM

no one here is using rf modulation
i think he just wants pass through

**meisner** · 07-15-2008, 07:45 PM

Exactly...I am still using my head unit and want an antenna. This is mostly for when others drive my car and just want to listen to the radio without a course in using a CarPC.

So I don't want RF modulation but still want a functioning power antenna to go up when I turn on the head unit (or choose Radio in DFX).

The way the RF modulation works (from the best I have figured out so far) is that the antenna IN (which is connected to the antenna) supplies the RF signal to the head unit radio when the HD radio unit is off (passthru). When on, the ANT OUT signal is generated by the HD radio box and not by the physical antenna. This supplies the HD audio to the head unit on a particular frequency.