Mine reports 2 antennas connected using this adaptor (http://www.ebay.co.uk/itm/FAKRA-VW-RNS-RCD-510-310-315-radio-antenna-aerial-adapter-Seat-Skoda-Columbus-/261163682162) but the signal is still generally poor. I don't bother using the radio that much as a result.
As for the roof antenna, it should only have a shark fin if the car left the factory with Nav or Phone. Seems a bit odd if someone retro-fitted the RNS 300 as you'd expect it to have come with that from the factory. Bee-sting aerial was fitted 2006MY on wards and the combined bee-sting/ shark fin is 2008MY on wards only.
thanks for the response, I have the same kind of adaptor but still only 1 antenna reported in the unit. No idea why it's not showing the second, just dont understand where it should be connected too as the roof fin only does phone / gps. So any idea's? The RNS 300 had 2 antenna connections and a gps connection too so that why I expect thaere should be another somewhere.
Strange thing about the Nav (300) was that it had the GPS receiver mounted aftermarket in the dashboard. Not connected to the fin on the roof. no idea at all? May I should try and find out what was standard by uncoding the sticker...
I've used that cable converter on my 08 to fit rcd510 DAB, and 1 FM comes from roof aerial, I guess the other 1 is diversity under the seat, I must try and find it now......
As far as I know RNS 300 and newer all do the diversity automatically in the head unit, under the seat diversity unit is only in <2005 or something like that.
/edit
decoded the sticker:
B0A = Component parts set without country-specific design requirement
CJ8 = Alloy wheels 6.5J x 16
G0K = 6-speed manual transmission
HH7 = Tires 205/55 R16 91V
J0L = Battery 340 A (70 Ah)
D7N = 4-cyl. turbo diesel engine 2.0 L/103 kW TDI with pump-jet injection system base engine is TM0/TP0/TR0
1AT = Electronic stabilization program (ESP)
1G8 = Breakdown set
1MH = Leather steering wheel
1NL = Covers for alloy wheels
5RQ = Right exterior mirror: convex
5SL = Left exterior mirror: aspherical
TM0 = 4-cylinder diesel engine 2.0 L unit 03G.7
0BE = Rear stabilizer
3S0 = Without roof rails/roof load rack
3U1 = Foldable trunk cover
QG1 = Service interval prolongation
8GU = Alternator 140 A
8ZN = Antenna
1KD = Disc brakes, rear
1ZE = Disc brakes, front (Geomet D)
3YR = Door pockets with insert mats
G07 = Front shock absorption
7GG = Emission standard EU4 DPF
0Y1 = Standard climatic zones
4UF = Drivers and front passenger air bag with front passenger air bag deactivation
4X3 = Side air bag front with curtain air bag
4R4 = Power windows with comfort operation andcircuit breaker
4K3 = Radio remote controlled central locking operated from inside and safe securing
N2N = Woven fabric seat covering
5MJ = Decorative inserts
8RM = 8 speakers (passive)
2JC = Comfort bumpers
E0A = No special edition
0AE = Front stabilizer
0BE = Rear stabilizer
2UC = Sports version
2G5 = Filler neck module 1 without insert
1JC = Rear shock absorption for sports design
L58 = Suspension range 58 installation control only, no requirement forecast
0YA = Weight range 1 installation control only, no requirement forecast
still doesnt tell me much, no idea what radio is standard on this.
this is the sticker: