Q From Haynes, Hi Line diversity question

[Keith]

Reebs and SD1too asked me about poor radio reception on his Hi Line car

Turns out he has one of the diversity channels missing to the radio in the boot (the smaller of the two coax connections) and when he examined his HRW he only had the standard single channel radio aerial amp with two wires going to the HRW i.e the same as a vehicle with a standard HU

At first I thought because his car is fairly unique it may have been a production line cockup but quickly eliminated that as even if they had fitted the wrong HRW and diversity amp that would not explain the missing coax in the harness.

Earlier Hi-Line cars had four wires but when I retrofitted Nav in my 2004 ZT I discovered the same issue, only two usable connections to my HRW, I had assumed there were always two types of HRW one with the extra connections for Hi-Line and one without

I now suspect at some point in time MGR standardised on one type and did away with the second diversity connection, this could lead to poor FM reception occasionally but explains why in Reebs case the entire coax connection was also missing from the harness.

This may have been a bit of MGR forward planning as later BMW radios only needed one FM connection

It would be interesting if those of you with later vehicles say 2004 on could confirm this, easy way to tell, if you feel under the radio in the boot just next to the big multiplug you can feel if the little coax plug is connected to the smaller antenna input or not

I checked Stangs V8 before being chucked out of Haynes and his was not connected either!

[John Robins]

Keith , I think this is another project drive casualty , on my first tourer build date 12/02 I had radio aerials in both rear side windows the current car build 8/03 only one window is etched . I have to say I've not noticed any difference in reception .

[raykay]

According to the list of Project Drive changes in your sticky 'really useful info' post 18, the diversity amplifier was one of the deletions.

[Keith]

Well done Ray I thought I had read something along those lines somewhere, so that is the reason solved even if Reebs still has naf reception!

Odd thing is perhaps the radio may still occasionally be looking for the other connection unless another project drive change was to disable the radios diversity function in firmware?

That is a real possibility I have a 1999 radio in my 260 and only the one aerial connection in use it also has bad reception or rather it often mutes and goes into search I will swap it with one of my later BMW units and see what happens.

[JohnDotCom]

A weird answer I find Keith when a FM station gets weak such as Radio 2, is if you turn off the TP on weak signal areas it comes back on and at a higher strength, switch back on TP and off it goes again either muted or searching for other stations, difficult in some parts of Wales I think the Mountains either side of road don't help!
Don't know why that would alter Signal strength though.

[Departed]

The radio doesn't look for the 'other' FM antenna, it never had two. The second connection is an output from the radio to the antenna amp, so the amp knows what frequency the radio is tuned to.

Then the amp selects the best possible of the FM signals and sends it to the radio. The radio only ever 'sees' one FM signal. If no diversity is fitted, it doesn't know.

HTH

[colinjyates]

Originally Posted by John Robins

Keith , I think this is another project drive casualty , on my first tourer build date 12/02 I had radio aerials in both rear side windows the current car build 8/03 only one window is etched . I have to say I've not noticed any difference in reception .

Hi,

Just seen this post, I have the ZTT and wondered why my heated side windows were not working! So they are aerial for the radio?! I assumed a the radio/tv came through the shark fin?

[JohnDotCom]

Colin,
The Side window "elements" on Tourer are the TV aerials. Other "elements & Shark Fin" are the Radio, and Sat Nav.

[Keith]

Originally Posted by lowedb

The radio doesn't look for the 'other' FM antenna, it never had two. The second connection is an output from the radio to the antenna amp, so the amp knows what frequency the radio is tuned to.

Then the amp selects the best possible of the FM signals and sends it to the radio. The radio only ever 'sees' one FM signal. If no diversity is fitted, it doesn't know.

HTH

Yep I understand how it works now it never occurred to me the little coax was an output controlling element selection but it makes sense

The diversity HRW is divded up in to four elements three FM and one AM it would be relativly easy to retrofit the diversity system if it is worthwhile and I am not sure it is. There may be side effects, I get interference and reception loss in my hi-line CDT with the HRW on that I don't get in the later non diversity equipped ZT

One would need the missing coax and mini connectors a diversity amp the four way connector lead to the hrw or improvise with a bit of DIY

I have all the above but did not use them in my hi line install because it all seemed to much hassle at the time

The only thing I don't have are the chokes to go in the earth leads on the bottom two elements of the HRW I would need to find some suitable values to give it a try

Slightly off topic I was considering abandoning the HRW element completely and instead looking at a glass coupled external FM aerial like those used for mobile phones if such a thing exists?

[JohnDotCom]

Perhaps something on these lines Keith but I know there is much better stronger ones out there.:
http://www.maplin.co.uk/module.aspx?...&doy=21m3#spec