Radio antenna?

[ss2115]

Hi. My radio constantly flips between stereo and mono with the accompanying change in volume and quality even though I drive in the metro area 99% of the time.

I realise that my car (1993 525i Touring) has the diversity antenna in the rear side window.

Whats the most popular or common solution to this problem?

Is it a matter of an inline signal amp, or changing to a different antenna perhaps?
What have most people found works best please?

[whiskychaser]

Hi. My radio constantly flips between stereo and mono with the accompanying change in volume and quality even though I drive in the metro area 99% of the time.

I realise that my car (1993 525i Touring) has the diversity antenna in the rear side window.

Whats the most popular or common solution to this problem?

Is it a matter of an inline signal amp, or changing to a different antenna perhaps?
What have most people found works best please?
Couple of questions just to clarify: does your radio show signal strength and mono/stereo? Does it flip between mono and stereo if the car isnt moving? Is it like that on all FM stations?

[leicesterboy15]

I have the same problem! I put it down to the fact that my windows are tinted but if you are getting the problem as well I guess not. I've tried running a cable straight from the aerial to the stereo, no difference. I've also tried an internal window aerial with a booster which is equally as crap. I haven't figured out how to get the side trim panel off to see what below there so I am thinking the only option is to drill a hole in the roof and use a roof mounted one, I'm putting it off because its a bit drastic and there are no guarantees it will be any better!

[BMWDriver]

I take it you guys have no problem with tapes, just to make sure the problem is not elsewhere.

[ss2115]

Couple of questions just to clarify: does your radio show signal strength and mono/stereo? Does it flip between mono and stereo if the car isnt moving? Is it like that on all FM stations?

Hi. No, there isn't a signal strength meter.
Its definetly flipping between stereo and mono - its like the difference between old AM (no high end quality, flat sounding and no difference left to right) and FM or even almost CD "sounding" - you can hear it seperate into left and right, the high end pops back and the quality jumps up several notches.

No, its only when the car is moving. If I stop in a place where it drops to mono, it stays mono and visa versa. Sometimes I'll be stopped in slow traffic and it drops to mono and then I'll only have to creep a few metres forward and it will spring back to stereo.
Its definetly signal orientated from the antenna.

[I remember having this same problem in a couple of Mazda's many years ago when they tried the rear window track idea in the RX4's (they may have been the first - I don't know) but it used to do exactly the same thing. Their antenna's were big "T" across the rear window above the heating tracks.]

I couldn't tell you if its on every FM station I have memorised because in reality I only listen to three stations in total - one 95% of the time but if there's a song or advert or something I don't like I might change to one of two other stations and then come back later.
But Yes - it happens equally on all three stations that I listen to.

No - it doesn't happen on the tape player - not that I use it much but I had the same idea in case it was a loose connection or something and the tape plays in stereo just fine without a problem.

[bubba966]

It could entirely be a problem in the radio itself, and not an antenna problem. Assuming you both still have stock radios. Why not pick up a used one at a breakers and try swapping radios to see if that fixes the problem? I can't imagine that a used stock E34 radio would sell for much of anything.

[leicesterboy15]

This is the third stereo I've had and they have all suffered from the same problem, they have all been good quality Alpine units. CDs are fine, its just the radio for me too.

[whiskychaser]

If the tape works fine in stereo its not the audio output amps as the tape and radio will use the same ones. As the radio works fine until you move, I'd have to agree that weakening signals are the cause. Of course FM travels by line of sight so if you are surrounded by tall buildings that wont help. But I'd start by having a look at the aerial amp to ensure its even powered up.

[tim eh?]

Doesn't the antenna amplifier 'choose' between a few circuits in the rear window? Maybe one of these is interrupted? Any bad spots on the rear defrost?


***- bottom of the page... http://www.bmwe34.net/E34main/Upgrade/Stereo.htm (shrug?)

[whiskychaser]

Doesn't the antenna amplifier 'choose' between a few circuits in the rear window? Maybe one of these is interrupted? Any bad spots on the rear defrost?


***- bottom of the page... http://www.bmwe34.net/E34main/Upgrade/Stereo.htm (shrug?)
I have seen that item before too. But my Kenwood CD player/radio has no problems at all with FM. You could try a different inline amp like this:
http://www.crutchfield.com/S-RZ0SWd7lbiE/p_12044UA60/FM-Signal-Amplifier.html
But I would want to make sure it didnt amp up all the white noise as well before I bought one

[leicesterboy15]

Doesn't the antenna amplifier 'choose' between a few circuits in the rear window? Maybe one of these is interrupted? Any bad spots on the rear defrost?


***- bottom of the page... http://www.bmwe34.net/E34main/Upgrade/Stereo.htm (shrug?)

The aerial in the touring is in the side window not the rear defroster. Any ideas where the aerial amp is in a touring? Real OEm shows the diagram from a saloon (sedan) even when you select touring.

[whiskychaser]

The aerial in the touring is in the side window not the rear defroster. Any ideas where the aerial amp is in a touring? Real OEm shows the diagram from a saloon (sedan) even when you select touring.
http://forums.bimmerforums.com/forum/showthread.php?p=16812675
(I read this as ' in the boot on the nearside behind a panel' ;))

[ss2115]

Doesn't the antenna amplifier 'choose' between a few circuits in the rear window? Maybe one of these is interrupted? Any bad spots on the rear defrost?


***- bottom of the page... http://www.bmwe34.net/E34main/Upgrade/Stereo.htm (shrug?)

Thats quite an interesting article on the selection of different "arrays" according to signal strength.

I have reason to doubt it applies to mine though because I've had my radio out several times recently while installing a full OBC and also to get the code from the dealer, and I only have one coax (thick) antenna wire wire to the radio. There is no thin coax to the radio either as a seperate plug or in the large multi-pin plug.

Does anyone have a photo of what this system should look like?
Maybe I have an empty plug I don't remember seeing and the thin coax has fallen down behind.

I'll also hunt out this amplifier in my Touring - it seems from most of the references that I should find it behind the panel over the left rear wheel or thereabouts.
My rear window with the antenna tracks is the right-hand rear window only (and demister on rear window of course).
As my car is RH-drive, is it likely that my amps on the right-hand side instead?

[whiskychaser]

I have a number of problems with that article which I couldnt find on the original site any more. Firstly, I couldnt find a (second) 1/8 coax either. Secondly, why on earth would the radio (which is a receiver) be transmitting an IF? An IF is a low level signal which is the sum/difference of frequencies you get when you add a received signal to a local source in the radio, usually a reference crystal. Thirdly, it seems totally illogical to be doing that remotely from the radio where there is no screening or tuned circuitry. It makes more sense to me if the aerial amp just gives dB gain and the radio selects which frequency it locks onto and processes. But hell, I dont make aerial systems for a living:D

[ss2115]

I have a number of problems with that article which I couldnt find on the original site any more. Firstly, I couldnt find a (second) 1/8 coax either. Secondly, why on earth would the radio (which is a receiver) be transmitting an IF? An IF is a low level signal which is the sum/difference of frequencies you get when you add a received signal to a local source in the radio, usually a reference crystal. Thirdly, it seems totally illogical to be doing that remotely from the radio where there is no screening or tuned circuitry. It makes more sense to me if the aerial amp just gives dB gain and the radio selects which frequency it locks onto and processes. But hell, I dont make aerial systems for a living:D

I agree.
Its seems a waste of time to feed a signal back from the radio to the booster when the booster can just scan between arrays and contantly update to the highest gain at its own output to the radio.

Its more a matter of compensating for turning corners and such as the window tracks are just dipole antenna's.

I don't drive between high buildings and such (city). I'm in the northern beaches area of Sydney and like most of Sydney, its a matter of hills and valleys and lots of twisty roads.
And before anyone comments that thats the main problem, every other car with standard antenna's cope easily without a problem - its only this BM.

[tim eh?]

Its seems a waste of time to feed a signal back from the radio to the booster when the booster can just scan between arrays and contantly update to the highest gain at its own output to the radio.





Yes I agree with you guys this would make much more sense. Even in the author's schematic there is no circuit for the radio to signal the booster. I have a schematic for my car - it appears I have the diversity amp but hardwired to a single antenna... I guess we probably all have the diversity antenna amplifier because the rear defroster runs through it too.

But still I think that's what I would check first - if a regular antenna plugged into that coax (at the antenna amp end) stops it from switching back and forth you would be zeroing in on the problem. There was a recent thread about where the antenna amp is in a touring it's not in the side panels I don't think.

***- wait leicester boy did that already and it made no difference... well wtf then... hope the schematic helps.

[Bo525i]

Exact location in a touring: http://www.bimmernut.com/forum/showthread.php?t=41344

[whiskychaser]

But still I think that's what I would check first - if a regular antenna plugged into that coax (at the antenna amp end) stops it from switching back and forth you would be zeroing in on the problem.

At the risk of being nerdish, you can calculate the length of aerial needed by simply dividing 300 by the frequency in Mhz eg 300/100Mhz = 3 metres. You cant have a 3m aerial but you can have a half or quarter wave. And if you want to be totally OTT you can 'tune' the coax length too:D. IMHO this would work well without the aerial amp. But substituting a good aerial doesnt tell us why the old system doesnt work properly

[leicesterboy15]

Exact location in a touring: http://www.bimmernut.com/forum/showthread.php?t=41344

Thanks! I've finally seen a pic of it! Only trouble is I can't see how that trim panel comes off, I can strip all the panels out except that one! How did you get it off (the panel that is :) )?



***- wait leicester boy did that already and it made no difference... well wtf then... hope the schematic helps.

What am I supposed to have tried? I'm a bit lost, this is not my forte!



I have a number of problems with that article which I couldnt find on the original site any more. Firstly, I couldnt find a (second) 1/8 coax either. Secondly, why on earth would the radio (which is a receiver) be transmitting an IF? An IF is a low level signal which is the sum/difference of frequencies you get when you add a received signal to a local source in the radio, usually a reference crystal. Thirdly, it seems totally illogical to be doing that remotely from the radio where there is no screening or tuned circuitry. It makes more sense to me if the aerial amp just gives dB gain and the radio selects which frequency it locks onto and processes. But hell, I dont make aerial systems for a living

I have absolutely no idea what any of that means, sounds good though :)

Isn't all this a bit OTT? What happened to the aerial cable going from the stereo to the aerial, the end. Is all this additional wizzardry really needed? Does it make that much of a difference?

[ss2115]

Exact location in a touring: http://www.bimmernut.com/forum/showthread.php?t=41344

Beauty - thank you.
Now I'll check it for power and that all leads are plugged in etc.
I actually hope I find something wrong, because I don't know what to do if its all working as it should.
Don't really want to install a standard aerial, although I'd consider a pillar antenna I guess but can they be retrofitted really well to look original and discrete?

[tim eh?]

What happened to the aerial cable going from the stereo to the aerial, the end. Is all this additional wizzardry really needed? Does it make that much of a difference?
Well no aerial is ideal for all reception, as WC mentions in his nerdy post different aerial lengths work better for different frequencies. And the amplifier gives a much stronger and smoother signal to the stereo.



What am I supposed to have tried?



I've tried running a cable straight from the aerial to the stereo, no difference. So does it still makes a definite switch between good/bad or does it just sound lousy all the time? The key is to get it to stop switching around then go from there. I was sure the problem would be in or around the antenna amp but if the signal is still switching after you bypassed it and you've tried 3 different heads then I don't have a clue... the antenna or antenna lead must be shorting against something somewhere.

[Bo525i]

Thanks! I've finally seen a pic of it! Only trouble is I can't see how that trim panel comes off, I can strip all the panels out except that one! How did you get it off (the panel that is :) )

Here ya go :) (mind that there´s an extra plastic pullpin on top, close to the philips screw)

"To remove the Front side panel:
· Begin at the right of the Front side panel and remove a 6mm hex bolt that fastens both it and the Grey
grille to the body.
· Next remove the Plastic pull-pin shown at the bottom of the panel.
· Remove a Phillips screw just to the rear of the Shoulder- harness reel cover.
· Finally, there are two T-25 Torx screws behind a plastic cover inside the Tie-down unit. The small
(nearly invisible) cover will pop out by prying it loose using a small screwdriver in a slot found inside.
· Now rotate the Front side panel out, and downwards, from the bottom and remove it.
To remove the C-pillar trim and Grey gri lle:
· Pull the edge-guard strip straight off the rear door opening to expose the edge of the C-pillar trim.
· Pull the rear seat shoulder cushion slightly forward, it’s held by a blade-type clip near the top.
· Pull the C -pillar trim piece outward and downward from the bottom and set it aside.
· Remove the other 6mm hex bolt holding the Grey grille in place.
To remove the Shoulder-harness reel cover:
· Remove the Phillips screw for the cover that was hidden by the C-pillar trim.
· Lift the reel cover upwards and set it aside."

[leicesterboy15]

Well no aerial is ideal for all reception, as WC mentions in his nerdy post different aerial lengths work better for different frequencies. And the amplifier gives a much stronger and smoother signal to the stereo.



So does it still makes a definite switch between good/bad or does it just sound lousy all the time? The key is to get it to stop switching around then go from there. I was sure the problem would be in or around the antenna amp but if the signal is still switching after you bypassed it and you've tried 3 different heads then I don't have a clue... the antenna or antenna lead must be shorting against something somewhere.

It was a while ago but I think it was just crap all the time, from what I remember it was worse when connected directly than if I used the standard car cable. I don't recall it switching, does that make a difference?

[leicesterboy15]

Here ya go :) (mind that there´s an extra plastic pullpin on top, close to the philips screw)

"To remove the Front side panel:
· Begin at the right of the Front side panel and remove a 6mm hex bolt that fastens both it and the Grey
grille to the body.
· Next remove the Plastic pull-pin shown at the bottom of the panel.
· Remove a Phillips screw just to the rear of the Shoulder- harness reel cover.
· Finally, there are two T-25 Torx screws behind a plastic cover inside the Tie-down unit. The small
(nearly invisible) cover will pop out by prying it loose using a small screwdriver in a slot found inside.
· Now rotate the Front side panel out, and downwards, from the bottom and remove it.
To remove the C-pillar trim and Grey gri lle:
· Pull the edge-guard strip straight off the rear door opening to expose the edge of the C-pillar trim.
· Pull the rear seat shoulder cushion slightly forward, it’s held by a blade-type clip near the top.
· Pull the C -pillar trim piece outward and downward from the bottom and set it aside.
· Remove the other 6mm hex bolt holding the Grey grille in place.
To remove the Shoulder-harness reel cover:
· Remove the Phillips screw for the cover that was hidden by the C-pillar trim.
· Lift the reel cover upwards and set it aside."

woohoo! Thank you! This info is golden and rare!

[Tiger]

Can't read all the post... Number 1 to make sure is that the amplifier lead by the head unit is hooked up to the radio unit regardless if you are not using factory amp. This must be hooked up because the antennae amplifier is also hooked up to this circuit.

Second is make sure the antenna lead is good... I can't remember but BMW antenna needs special adapter to hook up to regular receiver... Make sure this adapter is good... try a different brand.

If the above two is verified, then you shouldn't have the problem. I installed HD radio into my car and zero problem. I had a two different head unit before and were crappy on FM and worse on AM... I think what solved the problem was different antenna adapter.

[tim eh?]

It was a while ago but I think it was just crap all the time, from what I remember it was worse when connected directly than if I used the standard car cable. I don't recall it switching, does that make a difference?

yeah it makes a difference, - you don't have the same problem as ss2115. probably the 'turn on' wire to the antenna amp in your case.

[BennyM]

But seriously, that's pretty cool. I had no idea it worked that way.



At the risk of being nerdish, you can calculate the length of aerial needed by simply dividing 300 by the frequency in Mhz eg 300/100Mhz = 3 metres. You cant have a 3m aerial but you can have a half or quarter wave. And if you want to be totally OTT you can 'tune' the coax length too:D. IMHO this would work well without the aerial amp. But substituting a good aerial doesnt tell us why the old system doesnt work properly

[whiskychaser]

But seriously, that's pretty cool. I had no idea it worked that way.
I used to convert 40 channel UK CB units to get the US 40 frequencies and expand 120 channel receivers to get 200. This was totally illegal and was of course for educational purposes only;) I could explain how diversity antennas work. But this isnt a radio forum. Bottom line is, if there is a small coax back to the antenna amp from the radio head, its purpose is to help select whichever antenna in the rear screen is receiving the best signal. If there isnt one, I would suggest the antenna amp just gives some gain. Leicesterboy I fear whoever installed your tinted windows inadvertantly cut the trace on the glass and thats why you get poor reception. I hope you can prove me wrong.

[ss2115]

Armed with the helpful replies from this forum, I took out the trim etc and found the antenna amplifier exactly where stated.

No small co-ax coming away from it - only the large co-ax to the radio as I suspected it would be.

I was hoping like hell it didn't have power going to it and I could say "ah-huh" and fix it.
Alas, it has power when switching on the ignition switch to the accessories and ignition positions with the radio on.

The metal earth tab it is screwed to is still fully painted, so the best and only thing I could do was to use a serated washer between tabs and bolt it down tight to insure a good earth.

Unfortunately, there's no improvement in the radio performance.
Cannot see any breaks in the window track and I know the rear window demister works on all lines because its winter here now and I use the demister every morning.

Any more ideas anyone?

[tim eh?]

Well I still think that your problem is probably internal in the antenna amp... something gone haywire inside and switching to one of the antennas you don't have. The only way to check this though is to replace it, maybe someone else has a better idea- that's all I can think of.

edit- actually the way to check it is by plugging a different antenna into that coax and seeing if it switches around still.

[whiskychaser]

Well I still think that your problem is probably internal in the antenna amp... something gone haywire inside and switching to one of the antennas you don't have. The only way to check this though is to replace it, maybe someone else has a better idea- that's all I can think of.

edit- actually the way to check it is by plugging a different antenna into that coax and seeing if it switches around still.
I think switching between antennas is supposed to happen in something like 300th of a second so you dont notice it. It just sounds to me like signal to the head isnt good enough. So I have to agree the only way forward is to try with a different aerial or antenna amp.

[genphreak]

I found that the diversity antennae in my sedan barely worked with many aftermarket headunits. Insescant mono/stereo switching in metro FM zones where multipath should have been minimal was the most obvious symptom.

I found that later JVC units worked well/solved the problem. Sony may be good too- and stock headunits should be 100%. I had a top of the range (older) Kenwood from may years ago with a really good tuner (KRC-970) in the first place that really hated it (and was fine on the Hirschman in the e28 before that). Also a more recent cheap Chinese MP3/USB one that was crap with it too was fine in another car.

Not sure if the Touring antennae are much different, the modern Pioneer in my 95 touring works very well... just a few more expereinces for the melting pot.

[shogun]

try to understand the explanations here in German or run it thru google translate, the white cable antenna amplifier must be connected to the radio
http://www.7-forum.com/forum/5/schlechter-empfang-eingeschalteter-heckscheibenheizung-43338.html

[whiskychaser]

try to understand the explanations here in German or run it thru google translate, the white cable antenna amplifier must be connected to the radio
http://www.7-forum.com/forum/5/schlechter-empfang-eingeschalteter-heckscheibenheizung-43338.html
Yes the antenna amp must be powered up. But for the rest of it they are going off at a tangent.

[ss2115]

Yes the antenna amp must be powered up. But for the rest of it they are going off at a tangent.

I took all the trim off, found the antenna amp and it does have power that switches on/off with the radio (and ignition of course).

I think its just a lousy antenna system - the window track idea never worked well unless the area is dead flat and signal is strong.

I was hoping someone had gone down an alternative antenna route that worked really well and looked OEM on the car.

[shogun]

I have no problems with the window antenna. works well, and we have a lot of mountains and even there it works.
But that is probably also somehow dependent on the radio station network (antennas/senders?)



http://www.selfmadehifi.de/hifi/kfz-hu.htm

[leicesterboy15]

yeah it makes a difference, - you don't have the same problem as ss2115. probably the 'turn on' wire to the antenna amp in your case.

I opened it all up over the weekend and found that my blue antenna lead wasn't plugged in on the ISO loom so I connected this up and the reception is much better! Its still not as good as I would expect but I am putting that down to window tint film on the antenna window and having to use an adapter for BMW aerial cable.

Before I would have to search for stations manually but now auto search brings back plenty of results! The problem spanned across all three stereos because I was using the PO's BMW to ISO adapter and this connection was not in place in the adapter itself!

Thanks for all your help guys and SS...keep persevering! There are plenty of tourings being broken on ebay (in the UK at least), they should be able to provide you with an new booster at a good price even with postage, its worth a try if its cheap enough!