Car aerial mystery

Forums › Transport (cars, bikes and boats) › Car aerial mystery

linw

2849 posts

Uber Geek

#154472 29-Oct-2014 11:38

I have just installed a Chinese 2DIN head unit into my 2009 Lancer hatch (has short roof aerial) and everything works fine except radio reception. Using the car aerial feed, reception is weak but it isn't bad using a metre of wire thrown on the top of the dash! With the stock unit, radio reception was fine.

Sometimes this problem is caused by not powering up the car's aerial amplifier but I am sure my car doesn't have one.

I am perplexed by this and can't think what would cause it or how to fix it. Could a big impedance mismatch do this??

It is also a mystery how those short aerials do AM and FM at all!!

Hope someone can throw some light on this conundrum.

TIA.

1 | 2

3552 posts

Uber Geek

Subscriber

#1164236 29-Oct-2014 12:01

The antenna amp thing would be my first guess, what makes you sure it doesn't have one. Also the antenna will be designed for a slightly lower frequency than we use in NZ.

frankv

5680 posts

Uber Geek

Lifetime subscriber

#1164238 29-Oct-2014 12:04

I'd guess that, in installing the new head unit, you've somehow accidentally disconnected/broken the connection to the aerial.

linw

2849 posts

Uber Geek

#1164352 29-Oct-2014 14:42

@lxsw20 - I am not totally sure about the amp but saw some reference to the Lancer not having one. I asked for a definitive answer from the supplier of this car but haven't heard back yet. Not sure about the 'slightly lower frequ'. Do you mean the new head unit radio is designed for a slightly lower freq?

@franky - no, aerial connection is OK. I was careful with it and it does deliver a signal but it is not a very strong one as I get signal fades that I didn't get with the stock unit.

Thanks guys.

Stu

Hammered
8334 posts

Uber Geek

Moderator

ID Verified

Trusted

Lifetime subscriber

#1164366 29-Oct-2014 14:56

What sort of plug does the aerial leed have? Did you need an adapter to plug the aerial in to the new head unit?

People often mistake me for an adult because of my age.

Keep calm, and carry on posting.

Referral Links: Sharesies - Backblaze -

Are you happy with what you get from Geekzone? If so, please consider supporting us by subscribing.

No matter where you go, there you are.

linw

2849 posts

Uber Geek

#1164608 29-Oct-2014 20:31

No, didn't need an adaptor. Pretty std socket in both.

Stu

Hammered
8334 posts

Uber Geek

Moderator

ID Verified

Trusted

Lifetime subscriber

#1164611 29-Oct-2014 20:37

Doesn't sound like there's an amp then, if it's the old style car antenna plug/socket. Any way you can check continuity between the plug and the antenna on the roof? Just in case. Might have been a dodgy soldering/crimping job in the factory?

Edit: Spelling

People often mistake me for an adult because of my age.

Keep calm, and carry on posting.

Referral Links: Sharesies - Backblaze -

Are you happy with what you get from Geekzone? If so, please consider supporting us by subscribing.

No matter where you go, there you are.

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#1164612 29-Oct-2014 20:37

is there any way you can test the roof aerial connection eg induce interference of some way that is reliable, then if the sound comes out then aerial is connected (hence lesson to not buy Chinese clone), and if nothing then the aerial is suspect

Equinox IT

Cloud spending continues to surge globally, but most organisations haven’t made the changes necessary to maximise the value and cost-efficiency benefits of their cloud investments. Download the whitepaper From Overspend to Advantage now.

Batman

Mad Scientist
29760 posts

Uber Geek

Trusted

Lifetime subscriber

#1164614 29-Oct-2014 20:38

not saying this is definitely the case, but I've bought Chinese clones from mobile phones to tablets to iphone cable to anything you can name - I always regret it, and money down the drain

richms

28168 posts

Uber Geek

Trusted

Lifetime subscriber

#1164616 29-Oct-2014 20:39

If it is a stubby antenna it will have an amp on it, they put DC on the antenna socket to power them. Easy test with the old head unit, check the voltage on the antenna socket.

Richard rich.ms

Stu

Hammered
8334 posts

Uber Geek

Moderator

ID Verified

Trusted

Lifetime subscriber

#1164618 29-Oct-2014 20:43

The amped antenna usually have a different plug/socket, don't they? Then you can get an adapter with a power wire on it. Needed one with the wife's Nissan.

People often mistake me for an adult because of my age.

Keep calm, and carry on posting.

Referral Links: Sharesies - Backblaze -

Are you happy with what you get from Geekzone? If so, please consider supporting us by subscribing.

No matter where you go, there you are.

richms

28168 posts

Uber Geek

Trusted

Lifetime subscriber

#1164624 29-Oct-2014 21:10

Diversity ones usually do, but I have seen both the old style motorola and the iso antenna plugs used on factory amplified antennas when doing friends cars. Really once you have bluetooth the radio is just going to be idle so only one wanted to pay up for the power injector, then just put that on the blue power antenna wire from the headdeck.

Richard rich.ms

linw

2849 posts

Uber Geek

#1164698 29-Oct-2014 22:05

@joker/BigHammer - there is a signal getting through so there is continuity. At my house it sounds fine but I am in a favourable spot. When I travel a few k up the coast, the signal fades. Did it driving south into Wellington as well. NewstalkZB is a very strong signal so it shouldn't fade and it certainly didn't with the stock unit. Works pretty well with a metre of wire so there isn't anything obviously wrong with the unit.

@all - I have tried powering up the stock unit but it is not really possible unless I go the whole installation way as there is no way of turning it on. It is just a box with two sockets and no controls!

Tomorrow I will rig it up with 12V on the aerial. I will isolate the 12V with a capacitor just in case the head unit doesn't like it. There is an open circuit between the shield and centre of the aerial feed so that indicates no amp present. The new head unit is open circuit to DC between the centre and outer as well.

Just can't nail a definitive answer on the amp presence or otherwise with googling and no reply from Mexted Motors.

Thanks guys for your thoughts.

nickb800

2715 posts

Uber Geek

Trusted

#1164702 29-Oct-2014 22:12

As you found, any old wire does a half-decent job of picking up signal - is it possible that there is a break in the antenna cable somewhere, and the little signal that you are getting is being picked up by a few inches of antenna cable before a broken connection?

linw

2849 posts

Uber Geek

#1164710 29-Oct-2014 22:20

Hardly likely as it was fine with the stock unit and I handled it carefully when removing it and re-plugging it. Put it this way, if it is damaged, it must be a delicate flower!

linw

2849 posts

Uber Geek

#1164762 30-Oct-2014 06:10

Woke at 3.30 this morning with a Eureka moment! I firmly believe the answer has been staring us in the face.

For decades we have had 'standard' vertical telescopic aerials, that, while badly mismatched to the wavelengths required, produced enough signal for the radio front ends, with their agc systems, to cope rather well.

But now we have gone to even worse matched stubby aerials that must produce smaller output voltages. This has to be compensated for by either adding a stand-alone amp or by adding greater amplification in the radio front end. My car stock setup has clearly gone this latter route and all works well. Other manufacturers, at least with some of their lines, went the other route e.g. BMW, Mercedes, and Nissan.

But my new radio front end, surprise surprise, is designed to match the 'standard' aerial output so therein lies the problem.

My solution is to either use a better aerial (piece of wire!!) or add a signal booster and hope it does the appropriate job.

So, I am going to try a booster amp. Supercheap Auto have an Aerpro shark fin with amp for under $25 so will try that using just the amp part. Unless you guys have a better idea.

Do my deductions sound reasonable?

Thanks, all, for taking the trouble to help. BigHammer and richms were angling in!

1 | 2