club.liberty.asn.au

Hi, I'm after some advice.......

I've replaced my mac HU with a Clarion VX404AU, which I am very happy with, except for the radio reception. It's terrible. Yes- I have it all wired correctly- power to the antenna amp (confirmed with multimeter) at the amp in the rear passenger side C pillar, and I do receive reception for the major stations while the vehicle is stationary, but while in motion there is static. I am certain that my issue is poor signal strength being received at the HU. The factory antenna plug was the two pin type, which has been adapted to go into the Motorola style input in the Clarion, so only one of the antennas is being utilised.

Reception was fine with the mac unit.

My question is, is there a way to make use of the second 'diversity' antenna by connecting the two together? Would this effectively double the antenna area, increasing the received signal, or am I an idiot? I am suspecting the latter, and if that is the case, does anybody have a non invasive (i.e. not involving drilling through my car to put another antenna on the roof) solution to improving reception, e.g. would an additional signal amplifier help?

Thanks in advance

Are they actually a dual diversity setup. mine was a jap import but in the end i was sure one pin was earth and one was signal. This was a while back so could be wrong. Also is it 'adapted' using adaptors or just hacked up to fit onto motorolla plug?

Definitely the diversity antenna. Two distinct antennas in the rear glass- Australian delivered. Off the shelf adapter, but they only utilise one of the antenna wires.

how many wires does the amp box thingy have coming out of it. I'm sure the headunit still only sees signal and earth and that if there's two anetnnas they join at the box. In the wagons it was behind the plastic inferior panel at the top of the rear glass, not sure on the sedans though. With the adaptor unplugged test to see if the second wire that isn't used is an earth or not. Could be purely a shielding issue stuffing up the reception if the shielded cable isn't earthed

Two wires out of the amp- two wires to the factory HU. My understanding is that the Mac HUs switched between the two antenna inputs, based on which was receiving the strongest signal. Kind of a backwards way to go about it though....why not just provide a larger antenna, or stick the thing on the roof.....

Earthing......Yes- possibly. I'll check it out. Cheers.

Verify that your car's antenna booster is getting at least 12V. Subaru's booster amps don't work very well with lower voltage (and many aftermarket HUs only provide 11V, and/or the voltage can drop if you're using the HU's same output to trigger speaker amps).

Some "micro bypass" (parking brake bypass) devices warn you to not connect the HU's amp trigger output to both the bypass device and the car's power antenna lead (antenna booster). Apparently, some bypass devices don't play well with the booster amp.

In any of those cases, power the booster amp from the +12V Accessory lead on the car's radio harness (usually red wire on aftermarket harnesses).

I suspect Subaru added the diversity feature to many of their HUs due to the antennas being lower and smaller (where long ago they were taller rod antennas -- either manual or motorized).

Tying the two antennas together won't work. That will wreck the impedance, making things worse.

The twin pins on the round Nissan-style plug are indeed the center conductors of two separate coax cables, one for each of two antennas. The ground contact is on the outer body of that round plug.

You might want to verify that you have good continuity (as well as no short to ground) on the center lead of the coax antenna cable, all the way from the output of the booster amp to the tip of the Motorola plug on your adapter.

If you follow the OEM antenna cords down to the floor below your HU, you will likely find a normal Subaru-style AM/FM antenna plug (gray, rectangular plastic), like shown in this thread (the HU shown there is from a 2010 Legacy, but later USDM models still have the gray plug at the floor, and a "feeder cord" bridging from there to an antenna socket on the rear of the HU). If your car has that gray plug, you could use a single 18" Subaru antenna adapter instead of the two pieces you have now (gray Subaru to round 2-pin Nissan + round 2-pin to Motorola). Reducing the total length and number of interconnects can help improve the signal strength a little.

Another common problem on wagons is that the coax antenna cable inside the flexible conduit at the hinge eventually breaks. Search and you'll find more than a few threads where people talk about repairing those.

ADDED: Since the problem only occurs while you're moving, check that your new HU itself is well grounded. Many recent Subarus have a ground lead clipped onto a lug on the rear of the OEM HU. You can make a short wire with a similar male lug and a ring terminal at the far end, and attach that via one of the mounting screws on the side of the HU.

Thanks for the reply, and thanks for the fantastic write ups on other forms- it was a massive help to me for my install!
I've managed to reduce the issue by swapping out the adapter going from the factory loom to the antenna on the head unit. The previous one used was very poorly made. It's still not perfect, but it is now usable.
Thanks again for all of your tech advice.... much appreciated!

Forgot to mention... I checked the voltage at the antenna amplifier, and it never dropped below 12V, so I've ruled that out.