I  have a 2009 1.2 Roomster which has bad radio reception. The aerial is at the front of the car.
I have managed to locate the aerial connector behind the interior light and tried to check the resistance between the the cable and the aerial with a multimeter. It seems to be open circuit. Is there an amplifier in the base unit which will explain the open circuit or should there be some small resistance reading?

Also the aerial does not fully unscrew from the base. I can unscrew the aerial 10 mm then it just turns and will not come out. Should this happen or is the base unit faulty.
Does anyone know how much a new aerial and base will cost and what is the part number. I do not trust the ones on ebay.

Thanks
Martin

I know this is an old thread and the OP will have sorted this by now but I changed my aerial + base yesterday and thought my info may be of interest.

I bought an aerial base off eBay - https://www.ebay.co.uk/itm/GENUINE-REPLACEMENT-CAR-ROOF-AERIAL-ANTENNA-MAST-BASE-SKODA-FABIA-OCTAVIA-RAKU/112504702872

Removed the old base by popping the 3 studs that hold the covering up inside the car where the aerial is located, needed to pull one pillar cover off too so that the roof trim didn't crease too much.

Undid and removed old base - the wire connector has a clip that slides away from the aerial to release.

Installed new base and then found that the original aerial mast does not fit into it, so went to euro car parts and paid for a new mast that did fit.

All trim etc. replaced and aerial is working well now.

The anti theft bit of the old aerial made the threaded union too long to insert into the base I had bought, I probably could have used a grinder to shorten it but it was scruffy anyway so just got a new one.

The old aerial takes a pretty hard tug before it comes out due to the anti theft feature, I found it a lot easier to remove once the base was off and I wasn't worried about bending my cars' roof when tugging on it.

The footprint of the new aerial base is smaller than the original too so you can now see where the old one was, not even wonder wipes would clean the mark off.  I think the skoda dealer charge £35 ish for a new base and if I was doing this again I'd go with that for the footprint and the fact I could use my old aerial mast.