Radio Q

["Al Powell" <APOWELL@agcom.tamu.edu>]

KSMITH1@mailgw.sanders.lockheed.com posted about his radio:
> 
> The AM portion does not function except for noise.  The "amplifier" 
> (rear window heater/antenna interface) mounted on the left D pillar 
> meets all voltage and current tests described in the new Bentley 
> service manual.  Is that unit a likely cause, or is the radio itself 
> more likely to be defective, based on historical experience?  (Please 
> self suppress generic flames directed at Audi radios.)  With the 
> amplifier-to-radio coax cable disconnected at the amplifier, and a 
> wire connected to the coax cable center lead, one (presumably strong) 
> AM station was barely detectable in the noise.

Kirby, I believe you said you have an '88 90.  I'm not sure this 
information transfers directly, but here goes.

In the 1990 200, there are two antennas - one in the windshield which 
si FM only, and the rear window defogger doubles as a second FM 
(diversity) antenna, and as the AM antenna.  Even if the amplifier 
tests out OK (and you must have SOME ballsy meter, dude, as the test 
sequence for my car requires a test meter which will carry a 15-amp 
load!!!!!!!!!!!) it is still possible to get decent FM from the 
front antenna - but have EVEN WORSE THAN USUAL AM if the antenna lead 
from the rear is broken  (Yeah, I couldn't resist a shot...)

So if you have this dual-antenna and dual-antenna cable setup, I 
kinda wonder if the antenna lead from the rear may not be broken.  I 
have not dissected one of the cables, but I recall from past 
discussion on this list that Audi uses an unusual antenna lead cable 
which is not the usual RG-59 type, but instead has a super-thin center 
lead.  Seems to me that it could get broken easily.....

If you've really followed the complete amplifier test procedure, it 
should be OK...which leaves only the antenna lead and the radio 
itself.

All theory, of course.  It's possible the AM section of your radio is 
toast, I suppose.  Do you have another simple radio around which you 
can wire up enough to test, using the AM lead?

The cheapest test is THIS: buy a $15 Radio Shack fender mount antenna 
and any adapter needed to connect it to your radio's antenna input.  
Just hold the cheapie RS antenna in your hand, connect it to the 
radio, and see what happens to your AM signal.  If it improves, it's 
the antenna; if not, it's your radio.  (I have an old fender mount 
antenna which I use just for stuff like this.  It works perhaps 300% 
better for AM than that fakey-s**t antenna on the rear glass!!  Oh, I 
forgot myself again, shuckey-darns...)

If the antenna is bad, put a power antenna in the fender and improve 
your reception.  Abandon the factory setup.  Not expensive, and a 
good, simple fix.  My 200 is waiting for me to finish my dissertation 
and put the Hirschmann power antenna in the left rear fender.  And I 
couldn't care less about losing the "clean lines" of the car by 
adding a power antenna.  I liked the one in my 1984 5KT and have 
missed having a decent antenna ever since we bought the 200.

If it's the radio, chuck the sucker and get a decent one on the 
aftermarket.  Email me for information about inserting a new radio 
into the DIN-hole the original leaves....but remember I'm working 
from a knowledge base of a 1984 5KT and a 1990 200.





Al Powell                           Voice:  409/845-2807
107 Reed McDonald Bldg.             Fax:    409/862-1202
College Station, TX 77843           Email:  a-powell1@tamu.edu 
W3 page - http://agcomwww.tamu.edu/agcom/satellit/alpage.htm
"Baseball is 90 percent mental.  The other half is physical"...
...Yogi Berra.