Why do I have two coax in my head unit?

S

skategoat

New member
I just swapped my head unit for a Scion and found that the stock HU has two coax antennae connections while the Scion has only one input. I plugged in the bigger one and both my AM and FM work fine. What's the other one for?

Maybe my reception will go to crap when I leave the city?

Henry
2004 SR5 V8
 
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Second antenna. Other people who have done the scion swap haven't complained about crappy reception, so you should be ok.
 
I've noticed my reception isn't as good with my Scion unit than with my OEM unit. It's still plenty clear when I'm in a good location, but isn't quite the same. There's this one stretch about 2 miles long in my commute where reception is pretty bad. I used to be able to drive through it without any problems with my OEM unit, but when driving the Corolla or since I installed my Scion unit, all I get is a bunch of static. I guess it's a good thing I've got a 6-disc unit now, I haven't run out of music yet.
 
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i hav an aftermarket unit and also only plugged in the larger connection. i've noticed a decline in reception also (especially in parking structures), but i mainly listen to cd's so it's okay.
 
Both coax connections are for FM. The OEM unit uses what is called an FM 'diversity' tuning system. Internally, it looks for reception on both antennas and then selects the one with the better signal. This happens continuously while you're listening. The switching happens fast enough that you cannot perceive it.

Look at the rear quarter panel windows on your 4runner. You should notice an antenna on either side -- each with a slightly different pattern. These are the diversity antennas.

On paper, the two antenna system should always be better than a single antenna system. In practice, signal quality has much to do with the design and quality of the tuning circuitry. Thus it's possible that a replacement radio with only a single antenna might perform better than the OEM diversity design -- in certain circumstances.
 
I just drove to the cottage for the weekend - about 400kms. round trip and noticed no degradation in reception. I think it was actually better than my stock unit.

As for sound quality, the "Neutral" setting is dull like the stock unit. In "Hear" and "Feel", the sound really comes alive. One other thing, I can crank the Scion pretty loud without any distortion. I'm impressed.
 
tkr128 said:
I've noticed my reception isn't as good with my Scion unit than with my OEM unit. It's still plenty clear when I'm in a good location, but isn't quite the same. There's this one stretch about 2 miles long in my commute where reception is pretty bad. I used to be able to drive through it without any problems with my OEM unit, but when driving the Corolla or since I installed my Scion unit, all I get is a bunch of static. I guess it's a good thing I've got a 6-disc unit now, I haven't run out of music yet.
Click to expand...

The Scion unit has the 2 connections for the antenna. At least my single disc does. The second one is hidden though. If you take the radio apart you will see the smaller connector. You could drill a hole so you can use the second one. Maybe this will help your reception.

JT
jtaudioacc.com
 
So after talking to many audio installers and Toyota themselves, I now know that my 05' 4runner has a amplified antenna. I swapped out the head unit with a Alpine and now my receptions is really bad so I need to get power to the amplifier. I noticed the plug that I’m not using now and it seems to have four wires coming out it, which one do I hook 12v to and get the antenna amplifier working?
 
Second Antenna jack

Coaster is correct, there is a second jack.

I have read about taping up the extra antenna wire. However, I was curious so I started looking at the back end of the unit. I found that the SCION (single disc) head unit DOES HAVE A SECOND ANTENNA SOCKET for the smaller antenna wire! However, it is covered up.

I removed the thick metal heat sink, and one half of the sheet metal cover. The smaller jack is right next to the main antenna jack. (Remove the screws with the little arrows next to them.) I measured the location of the second jack and drilled holes in the sheet metal, and the thick cast aluminum heat sink. Reassembled, and installed.

I can attest that the reception is better than my original 4R unit.

WARNING - Do not drill holes with out removing the parts being drilled. You DO NOT want little metal chips in your Head Unit!

Thanks Everyone,
Whitney
 
Re: Second Antenna jack

whitney8 said:
Coaster is correct, there is a second jack.

I have read about taping up the extra antenna wire. However, I was curious so I started looking at the back end of the unit. I found that the SCION (single disc) head unit DOES HAVE A SECOND ANTENNA SOCKET for the smaller antenna wire! However, it is covered up.

I removed the thick metal heat sink, and one half of the sheet metal cover. The smaller jack is right next to the main antenna jack. (Remove the screws with the little arrows next to them.) I measured the location of the second jack and drilled holes in the sheet metal, and the thick cast aluminum heat sink. Reassembled, and installed.

I can attest that the reception is better than my original 4R unit.

WARNING - Do not drill holes with out removing the parts being drilled. You DO NOT want little metal chips in your Head Unit!

Thanks Everyone,
Whitney
Click to expand...
Any plans to post a write-up and pics?
 
Write up.

Jharris,
I was so excited to get the new SCION unit powered up that I totally forgot to take pictures! My appologies!

It really wasn't that hard, you just need to be take your time and be careful of the printed circuit boards, because once you remove the protective sheet metal they will be exposed and vulnerable. Do not touch them, electrostatic discharge can be the death of PCBs.

Before you start, take a close look at the back of the unit, just above (or below, can remember) the main antenna jack. If memory serves, you can see through the holes in the sheet metal that there is a cyliner above the main jack, this is your second antenna jack! Take a pencil and mark a line straight up from the main jack, then you have to estimate (or measure if you can) how high to put the horizontal line. This will serve as cross hairs for the hole.

Now remove the thick Heat Sink at the back. There should be at least 4, maybe 6, screws (the ones with the little arrows next to them).

Now make a second set of cross hairs on the sheet metal piece. (Just in case, keep the heat sink screws separate from the sheet metal screws.)

Now comes the hard part: removing the sheet metal. It will be clear which half to remove. Again, remove the screws next to the arrows. The other thing to watch out for is the little plastic tabs that help hold the sheet metal in place. This is one of those times that it would be nice to have a third hand, because you have to carefully lift (and/or push) the fragile plastic tabs, while at the same time, lifting and pulling the sheet metal piece off the unit.

Once both pieces are removed, take the cast aluminum heat sink and transpose your cross hairs to the back side. This will give you a flat surface to drill into. Take a center punch and make a dimple. Start with an 1/8" hole with high RPMs, follow up with a 3/8" bit with LOW RPMs. If you did not locate your holes very well you may need to enlarge the hole(s). ;): Be careful when you are about to break through, because the drill will catch the piece and could injure you hands (a vise would be a good idea).

Next do the same with the sheet metal. Clean up the sharp edges with a dremel or a file.

Reassemble, and try not to break any of the plastic tabs. :p

And there you go!
 
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This is for jelgas for a problem he posted a few days back -

I too have an Alpine head unit that I installed in my 2004 4Runner. There is indeed an antenna amplifier in the headliner of the 4Runner that must be powered to get good reception. I found the best way of accomplishing this is to use the terminal on the Alpine that is designated for a power antenna. This is ideal because it only applies power when the radio is being used (originally intended to raise your power antenna). This lead will connect to the 4Runner's radio harness at plug R2A Pin# 8, a black wire.
 
the irishman-

thank you for the help I did manage to figuer this is out last weekend and did excatly as you said. It did get my problme solved. I'm just now trying to decide what to do with the low tire presuer light deal. After changing the rims I discovered tps situation. uggg!!

thanks all
 
I know this is a little late. I found I did not need make any modifications to power up the power antenna. If you are using a wiring harness; make sure you connect the power antenna cable to power. I just connected the "power antenna" cable from my Kenwood to the "Power antenna" connection on the harness.
 
my04runner said:
I just ordered a new Kenwood head unit for my second 4runner. However my wife would like to avoid the reception decrease. I found this and it looks like it would fit. Anyone else think its the right one? It says for Nissan but the ends look about the right size.

http://www.sjgreatdeals.com/sisndab.html
Click to expand...
Hard to tell from the picture. Two suggestions:

1. Call or e-mail them and ask (use the "Contact Us" tab on the upper right; or,

2. Gamble the cost (<$4.00 plus shipping) and try it out.
 
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