Radio not getting proper signal

OK, story time.

Symptom: Radio is getting very poor signal, only some of the strongest stations can be heard.

Diagnosis, round 1: Remove stock (Skoda) radio (actually Grundig MS201), swap radio to another radio (Panasonic), no help at all. This unit has CD so no hurry.

Diagnosis, round 2: Buy ordinary antenna, connect it to radio and notice 12 new channels even without ground contact. Nice. So it's an antenna problem. This works so no hurry.

Diagnosis, round 3: Find a Youtube video of how to access antenna on the roof (-00 estate so it's in the back) and notice it's actually simple, just remove the plastic rear panel from the roof and one panel stud holding the soft roof in place. Nice. Disconnect 2 wires (radio & GSM) and use a 22mm wrench to open the nut keeping the roof unit in place. Notice that absolutely 0 connectivity between roof unit chassis and grounding point leaning to roof. OK, problem #1 (pic PB162179.jpg sorry for quality on that): Rust on the steel ring on the left, thoroughly black ("rusted") brass nut on the right and unit body on top. Grounding is supposed to go from roof to steel ring, from there to nut and from there to unit body.

Only connection actually working was between steel ring and roof. Cleaned steel ring and nut with sandpaper and thread with Autosol (good stuff). OK, connectivity achieved, put everything back. Still no good reception, problem #2.

Diagnosis, round 4: Use ordinary antenna bought in round #2 to check if the wiring in the car is OK by connecting it to the connector in the car by a simple wire. OK, 16 channels or so, great. So no problem in wiring in the car side.

Diagnosis, round 5.  Disconnect roof unit and remove it from the roof, notice no change in reception, so basically I'm listening using antenna wiring as antenna. No wonder reception is very poor. Lift ordinary antenna on the roof, connect it to the car wiring with piece of wire and notice 8 new channels. Ooh, this is good. So only thing I have to do, is to cut ordinary antenna wire, solder the old wire to it so I get the stock connector and all is fine. I do that, still poor signal. WTF! Problem #3.

Diagnosis, round 6: Remove antenna from the car and measure the wires: No connectivity on +-side, grounding is OK. WTF? My own joint failed or what?  Tear the joint open (BTW. not easy at all when you've used shrink wrap with glue, which I did), notice that from joint is OK and from joint to antenna connectivity is there, but not from joint to connector. WTF!? OK, Problem #4.

Diagnosis, round 7 and solution: Rip  the connector open and it's oxygenated to oblivion, +-side wire basically isn't there any more. - -side exists but severe oxidation. Ouch. Obvious reason for poor reception. Go to shop, buy an adapter with correct connector (Raku II male in this case)  on the other end, cut the wire, throw the other end away and solder the remainder  to the wire coming from antenna. Install whole circus to car and notice you have 24 radio stations now. OOOH! Success.

No worries, put panels back and that's that and ordinary people would have stopped to this and dumped the non-working parts to dumpster.

But I'm curious guy so I wanted to know how can wires oxidize so bad? Basically whole wire from roof unit to connector was black and copper wire shouldn't be black ... where the water/moisture has come? Leaking roof?

Diagnosis, round 8: No signs of leaking roof, so I disassembled (with very much brute force) the roof unit. You could have opened it with two screws (under the glue) but too fancy: This is a scrapped unit anyway. What I found was basically trash: Rusted and oxidized components of something what has been a RF-filter splitting signal to GSM- and radio-segments. Worst condition for piece of electronics i've seen in long time. See the other 3 pics.

The PB172182.jpg shows the reason why the wires were so bad, as it shows the roof unit end of the wires and as you can see, there's nothing at all blocking water entering the wires. Thick black section goes out and small red wires feed them ... see how the copper is totally black and capillary force nicely pulls that dampness all the way through wire.

Usually this kind of outputs use hot glue or something like that as dampness prevention. And of course lacquered circuit boards. These ones don't have anything at all, as if this was designed to normal office environment and not to roof of a car.  Ridiculous level of cost savings, if you ask me.

A least the case was glued shut but obviously that wasn't enough.

Anyway, that's the end of the story: None of the old pieces were usable so they went to dumpster. New antenna sits on the roof and I've full 18 channels to choose from (no more memory slots in radio) + some less important on top of those.