Rear window aerials

The radio in my (ex-Vamps) 328i uses the back window heater as the aerial.

It's crap.

Or rather, sometimes it will pull in loads of stations, then suddenly you get one or two local stations and Classic FM. The last one is probably because it got burned in when it was Vamp's car ;-)

I gather it's a box on the C-pillar somewhere that acts as an FM aerial amplifier and has an 'on' signal fed to it from the radio. so...

Vamp, did you wire that signal on when you fitted the new radio?

For everyone: are they 'all like that, sir', or is it buggered?

Shall I just get an electric or bee-sting aerial for it instead? How about a natty little sharkfin with a built in amplifier, do they work any better?

Reply to
PCPaul
Loading thread data ...

Yup. They all are.

If it's the same as my 528 it has two aerials in the window and the aerial amp selects the best one - called diversity reception.

Well, if reception is intermittent something is up.

The roof is the best place for an aerial. The steel roof acts as a ground plane and improves efficiency - although to get the best effect the aerial would need to be mounted in the centre of the roof like police cars. An ideal length aerial would be too long for a car so it's more usual to use a less efficient but smaller one and add an amp.

However I've no idea if a 'stock' aerial of this type could be used with your BMW system - all sorts of things could be different.

I'd first make sure all the connections to your amp are sound. It should work ok on FM - provided you don't stray too far from a transmitter.

Reply to
Dave Plowman (News)

You could always fit one of those BFO aerials where the end clipped to the back of the car, like my dad had in the '70's

Reply to
Abo

I was thinking two, really. Bright yellow ones, one each side.

Reply to
PCPaul

Ah righto, so the one on the back of the Merc doesn't work well then?

That's odd, because I've never had reception problems, not even in Italy where the external rod aerial on the Ford doesn't provide enough signal.

Or perhaps the word "all" was accidental?

Reply to
Steve Firth

I thik the amp for the antenna usually runs off the wire that a power antenna or amplifier remote would use.

Normally the blue wire from an ISO plug headunit tail I think. Don't know if BMW use the same, but in the Saab 900 it was green through to the boot/antenna from behind the dash.

Reply to
carl.robson

It's white on the BMW - I haven't dug the radio out yet to check if it's connected right, but I have just been under the trim and tightened the connections. Forgot to take a multimeter out and check the voltage though..

I'll check it's the 'remote power amp' wire that's used, not the 'power aerial' as the aerial one is an up/down pulse at switch on/off, not a constant +12V supply like the amp wire should be.

Reply to
PCPaul

Nissan diversity uses a "proper" electric aerial in rear quarter in addition to the window element. Aftermarket radios only have one aerial socket so use an adaptor that both plugs go into, could do the same just by splicing the cables together on one plug.

Reply to
Peter Hill

There'll be an ideal spacing between aerials for diversity to work at its best - but I doubt it's achieved on a car.

The BMW system uses an aerial amp to select the best signal and then sends that on to one fairly standard input on the radio, IIRC. Proper diversity systems use two complete receivers and switch between the audio outputs.

Reply to
Dave Plowman (News)

Correct - for mine anyway. two flyleads from the box to the rear screen elements (plus ground), but only one coax to the front.

The coax does go through the boot-hinge loom though, and I have already had to replace the central locking supply wire that took the same route...

I'll just have to beep it all through and see what happens...

Reply to
PCPaul

Hmm, thats an odd one. Normally a headunit remote is a constant 12v. I've used it before to trigger a relay for a permanently on inverter before.

A power antenna usually has an internal relay for up/down switching.

Reply to
Elder

LOL, an old 70's CB whip. Fabulous.

Reply to
Elder

ok there's a box under the drivers seat i think! can't remember, there is also a white aerial lead on the iso plug i suspect this is the fault, i did have a booster fitted when i had it but that was no good. i think it's that white cable and i don't think it's getting enough or any power as i've taken the radio out a few times fiddled with the aerial plug and white cable. put it all back and it's fine but i did have to mess with it a few times. it had a aftermarket kenwood when i bought the car and the white cable was in place but i'm not sure if it's getting any power as i could never find my meter to check.

i was going to fit an aerial from my mates old volvo which went in the front bumper, i was going to put this into the BM but my mate scrapped the volvo with it still on there cos it was exactly the right length to fit behind the bumper, forget which model volvo though but his radio worked great! the rest of his car didn't mind lol

Reply to
Vamp

I'm pretty sure there's only the box under the C pillar trim - unless you added another one...

No problem, I'll check it out.

Reply to
PCPaul

Elder gurgled happily, sounding much like they were saying:

Yup, the Kenwood (?) head unit in the Saab's definitely an on=+12v, off=nothing.

Yup, the Saab aerial has a permanent +12v plus the feed from the HU - it needs it, because the aerial doesn't start to motor down until the HU powers off, which is when I turn the key off. I can be out the car and the door locked before it's fully down...

Reply to
Adrian

i didn't but i'm sure it was under one of the front seats, i think it should be a white box too

pull the head unit out you'll see the white cable, i'm still not convinced it's getting power

Reply to
Vamp

Obviously I'm more easily satisfied, because I'm not that disappointed with the radio in my E39. Faiir enough, the sound quality could be better, but reception on FM, which is all I use, seems fine. I miss the lack of sound quality most when listening to CD's, as I know how well they sound on a decent system. Mike.

Reply to
Miike G

The 900 and the 9000 were both the same, and both had aftermarket headunit, usually cheapish ones, so just the standard iso wiring, with one remote live.

Reply to
Elder

most BMW's i've been in have had pretty weak reception. even my mini didn't have a brillant reception. although strangely when i changed the factory head unit for a kenwood it seems to have improved, i now get the trafic reports without them cutting in and out. normally right at the point where there about to mention the route i'm about to take!

Reply to
Vamp

It's the AM that shows how bad it is. Or a poor signal area for FM.

Yes - the factory fit speakers in my previous E34 sounded much better. The E39 has strange twin voice coil speakers for use with a phone. I've not investigated fitting better units as I usually just listen to R4.

Reply to
Dave Plowman (News)

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.