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[TheBoy]

Possibly one for that nice DTM fella....

I had her watching BBC One East all the way to mums on Saturday.  Once past Northampton, picture quality was OK-ish, but audio was constantly breaking up - initially we though headphones, so turned off dual view so I could hear it, and it was still breaking up.

FM - it's picking stuff up, but very few stations have and RDS info.

Given DAB is struggling to pick up much, does this point to the antenna amp?  If so, does it have a fuse?  I can't find the amp on the schematics I currently have downloaded (and not sorted my TOPix access back yet, LOL)

For reference, its the B&W 1200W system in mine with the gen2.1 HDD IAM/Touchscreen setup, if that makes a difference.

[Viral_Jim]

Assuming yours has the antenna in the window glass, I'd be tempted to look closely at these first of all.

I had similar problems with FM radio in my first Saab 9-5, turned out that  this was my issue. One quick insurance claim later for a busted window and all was well 

[Marks DTM Calib]

Will have a cat with the antenna team today, the usual cause is grounding issues rather than the amp (which is pretty bulletproof and either works, or doesn't work).

You can get straight into Topix using your other halves cdsid (or message me)

[TheBoy]

You can get straight into Topix using your other halves cdsid (or message me)

Yup, I can never remember the new password, LOL.

I did have a poke around in topix, but cant find anything on them, and very limited in the wiring diagrams.  But it did help locate the amps....

[TheBoy]

So there is an antenna amp on both C pillars.

NS:


And this is what I think is the power feed:



OS:


power:

[TheBoy]

Currently, on my driveway (which is always problematic), I can get most BBC and some independent like Great Hits Radio on DAB, and a handful of stations on TV.

If I unplug the power from OS antenna amp, it makes no difference to DAB or TV.

If I unplug the power from NS antenna amp, I lose all DAB, but makes no difference to TV

With both unplugged. I lose all DAB and makes no difference to TV


(I forgot to check FM whilst doing these tests)


In addition, my understanding of the wiring diagram (INFORMATION AND ENTERTAINMENT SYSTEM Part 1 for Mr DTM) is that the IAM provides power to the antenna amp(s) directly, presumably when turned on.

However, I was seeing 0V on that power pin* whether the system was on or off (but never tried with ignition on, maybe I should have? But the radio/tv should work with audio on, even if ignition is off?)

*I used a normal sewing pin pushed into the connector to attach a croc clip, and the 0V was from one of the the rear ciggy lighters.


Viral_Jim - screen elements look in tact, though due to number of antennas, and the fact its also HRW, I can't be absolutely certain about what is a design break and what could be damage, though all the breaks in the wire look clean cut and a similar 1mm ish gap

[TheBoy]

With regards to the NS antenna amp, not quite sure how it works with 2 wires from rear window, and 4 coax cables off to the various devices.

[Marks DTM Calib]

Lets go in stages.

The NS amp supports the FM2 / DAB_3 / TV3 / TV4 bands, it uses the specific antenna traces you can see at the top of the rear screen for DAB_3, and the heated screen for the others

The OS amp supports AM / FM1 / TV1 / TV2 and uses the heated screen traces for all.

There are multiple outlets as the various different bands used are amplified, split, and filtered within the amp module so that only the frequencies of interest are fed to the relevant module (so DAB module, TV module, IMC).

It is VERY important that the ground connection on the amps is clean, corrosion free and tight, this is worth checking  and I think it might be the mounting foot in this case.

[TheBoy]

So DAB is only on the NS?  I'm near certain I read somewhere on topix that DAB is both sides (or that there are 2 antennas, at least).  Could certainly explain why it made no difference to DAB when I unplugged OS amp.

I will certainly check grounding, though it looks clean and tidy up there.  Its a bit of a pig to get to as the head restraint is in the way, and, yes, you guessed it, the seats have to come out to remove them!!   Could I try by using a lead with a pair of croc clips, one connected to the amp's body, other to a known good 0V?

[TheBoy]

Removed NS - looks OK to me from a 0V perspective. https://theboy.omegaowners.com/jag_pics/XJ_Audio_Antenna/IMG_7313.jpeg

The stud it mounts to looks like it was painted with the car, then the nut screw over.  I've put a small wire brush on the stud, but not gone mental.

[TheBoy]

Rear window:
Red lines show what look to be very intentional breaks in the element, cleanly cut and about 2mm gap.  Yellow and blue lines show (presumed) connectivity of whats left, unclear if the blue and yellow are connected from original topix diagram, guessing not, and the edges of the element go into the black areas on the screen making it impossible to see.

Additionally I can't see very top wire in topix diagram, as that too would be in the black area of screen.

[Marks DTM Calib]

So DAB is only on the NS?  I'm near certain I read somewhere on topix that DAB is both sides (or that there are 2 antennas, at least).  Could certainly explain why it made no difference to DAB when I unplugged OS amp.

I will certainly check grounding, though it looks clean and tidy up there.  Its a bit of a pig to get to as the head restraint is in the way, and, yes, you guessed it, the seats have to come out to remove them!!   Could I try by using a lead with a pair of croc clips, one connected to the amp's body, other to a known good 0V?

I am just awaiting a call with Rich, I recall there being another antenna, possibly rear bumper, for DAB as well.

The nuts used are paint clearing nuts.

Any extra ground connection needs to be very good and very short, as the frequencies being used are pretty high and you need the loop impedance low

[Marks DTM Calib]

Removed NS - looks OK to me from a 0V perspective. https://theboy.omegaowners.com/jag_pics/XJ_Audio_Antenna/IMG_7313.jpeg

The stud it mounts to looks like it was painted with the car, then the nut screw over.  I've put a small wire brush on the stud, but not gone mental.

Get that bracket and the nut contact face super clean, there will be some capacitive coupling but, a good ground helps a lot

[TheBoy]

OK, ta, I'll get a wire wheel on the amp's lug to shine it up a bit, and then get it put back on, as I don't think there are any more I can do with it off?

Actually, let me pop the top to check any case to PCB contacts....

[TheBoy]

Actually, let me pop the top to check any case to PCB contacts....

Poxy security allen, not get any of those on me today.  Meter has all screw heads as 0.00 ohms between screwheads and the amp's metal casing.