Date:         Sun, 25 Sep 1994 09:40:44 -0700 (PDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Wes Neuenschwander <wesn@eskimo.com>
Subject:      Re: Radio problem

> > 
> > Check the antenna cable/antenna connection, or perhaps try replacing the 
> > antenna and cable.  This definitely sounds like a poor antenna connection 
> > to me.  Also, some radios (typically older ones) have an antenna trimmer 
> > adjustment that tunes the radio to the antenna.  Look for a slotted screw 
> > type adjustment - probably labelled ANT.  Adjust while listening to a 
> > weak station.  Otherwise it's probably new radio time.  
> > 
> Wes: Thanks for the reply: I checked the connection on the antenna b y
> removing and cleaning it. Its
> the standard Vanagon vertical antenna coming from the drivers side. The
> connection itself (both ends) is solid and the antenna itself is clean.
> The trimmer (pot) has also been adjusted for maximum gain. Since the noise
> exists even when the engine is not running, I have ruled out (perhaps
> incorrectly) engine/electrical intereference - it is not the typical
> whining sound one hears in these situations.
> I had hoped someone might say oh yes this is your xyz and will cost zyx to
> replace. My key concern is to fix it rather than replace the radio (I like
> the Alpine setup and assume its expensive to replace). BTW does the fact
> that the radio is not hooked up to the ignition have anything to do with the
> problem - it seems the VWs don't have an accessory position for  the key
> so the radio can be run even with the ign. off.
> 
> Thanks - DC
> 
I still think the antenna system is the likely culprit.  Even if the 
connections look good, they might not be electrically sound.  In 
addition, you may have a short (either DC or RF, via excessive 
capacitance) between the antenna and ground.  Definitely sounds like a 
low signal problem, as evidenced by the fact you are getting noise.  
Radios are equipped with an automatic gain control (AGC) circuit that 
will turn up the amplification to match the available signal.  When the 
only signal is ambient noise, the gain will be high.  When there is an FM 
station as signal (typically much higher level than noise), the gain is 
reduced, dropping the noise portion below audible levels.  Technically, 
this is referred to signal-to-noise ratio (S/N).  A simple check would be 
to substitute another antenna - doesn't even have to be installed, just 
make sure it's connected and grounded to the car body.  An even quicker 
check, though not as conclusive, is to attach a short section of wire to 
the center terminal of the antenna jack.  If S/N improves, this suggests, 
again, a bad antenna system is your culprit.  Another substitution type 
test, of course is to plug in another radio - doesn't even have to be 
installed, just attach to power, speaker and antenna - but this is way 
more hassle, and may not be as conclusive as the antenna substitution (it 
may be more tolerant of the defective antenna than your radio is). Bottom 
line is (IMHO):  If it isn't the antenna, it's the radio.  And even if it 
is the radio, keep in mind, what was a $500 Alpine 3-5 years ago, can now 
be had new for $100-200.  I've even seen new CD players for $250 
dollars.  

 --------------------------------------------
Wes Neuenschwander
Seattle, WA

(wesn@eskimo.com)