Howdy Krew,

This isnt a K question as such....but its an accessory fitted to my K so good enough

I have a marine stereo installed on my bike. It plays digital files from a USB stick, and it also has an AM/FM radio. I really like listening to the radio - particularly all flavours of the ABC.

Anyways, I have never been able to get the radio to pick up a good signal. I have a rubberised bendy antenna installed on the front fairing. The radio will only get a clean signal if I am touching the antenna's cable. 

Do I simply need to ground the antenna? Perhaps its designed to go through a car roof and be grounded on the sheet metal? I did try earthing it with a bit of wire but no luck. It was a bit of a half ass attempt though, using what I had on hand at the time....

Anyways, hoping one of our electro-gurus will point me straight. 

Cheers all,

Floyd

Stretching my limited memory of radio basics, the antenna usually requires a "ground plane", which is more than just a wire. 

As you say, in the old days, the metal of the car roof or mudguard did this job. I've also seen a 1ft square piece of metal under the roof of a fibreglass half cabin boat which has the aerial attached through the middle. 

I've not experienced a radio on a bike, but given the fairing being available, I'd be inclined to put a piece of thin aluminium sheet behind it, more or less centred on the aerial mount and grounded to it. Aluminium because it won't rust and can be easily shaped and cut to fit the curves of the fairing. 

Interested to read contributions from people with more expert knowledge or better memories. 

Bill

The R100rt Fairing I had on the K75c when I bought it had an CB aerial on the right side and a radio on the left it was one of those short rubbery ones with a pivot point at the attachment to the fairing so it would point up, my radio was above the instrument binnacle so maybe it provided a ground plane effect that way, it did have an earth wire to the frame though and worked a treat. I went through a heap of them plane car radios from the wreckers, one day though I'll invest in a marine radio so as to keep them for more than a year or so.

You don't really need a ground plane for good reception it's only necessary for transmission of radio signals and even then you can get antenna that dont need a ground plane but they are usually only for the UHF CB.
Usually if you get a big improvement in signal by touching the antenna it means you are a good antenna. To explain it would take around 10 pages and boredom would kill you.
It is quite possible that the radio need a strong signal and that wont happen unless you are near the transmitter. Maybe tie a real long bit of wire to the antenna and let it fly in the wind.

your little rubber duckie type antenna is the issue Floyd

from memory all of about 3 inches of them actually act as an antenna ....have you tried a automotive type antenna (after market type ) the ones that are about 300 mm  long and extend ?

Thanks gang

Ill try a big arse wire antenna soon and see how it goes

I have an original BMW K100LT aerial available if you want to try. Rigid, maybe 18" long (dont like to brag though)

Al

AL-58 wrote:I have an original BMW K100LT aerial available if you want to try. Rigid, maybe 18" long (dont like to brag though)

Al

  SO i should take 3" off that to get an accurate measure? Still rather 'generous' in proportions.

Thanks for making me aware there was a stock BMW item for this. didnt even consider it. According to the diagram there is a thick-ish earth strap-on. Might give that a try on my 12" floppy rubber member and see if i can induce a response. 

Didnt notice the earth strap, but then the RT is ex police and there are additional earth straps everywhere (I cut them off whenever I find them, just a nuisance)

Al