radio reception

Could be several reasons , including that it could also be bad on fm but its harder to tell because of way Fm locks in weaker signals so they sound strong.

- as a first step attach 20 ft or so of wire to aerial and note if reception improves markedly on AM

Robin Miller

I fitted a powered signal booster to my alpine head unit and found it instantly killed all AM reception.

Took booster off, AM returned.

While on it did nothing for better FM reception either

hope this helps

Rolande

Hi Hurkmagurk,
It may pay to check the continuity of your antenna lead, tho this can be masked by some antennas having a capacitor built into the lead, preventing the continuity check. A brand new antenna I once bought was open-circuit in the lead.
If you've got hash/buzz with a diesel running, the first thing to be looking for would be your alternator. A decent suppressor across its output may help. This is generally characterised by a whine in the hash, which will increase in frequency as the engine is revved. Also inline filters are avail from car audio shops to filter the DC into the radio.
Also, I found when I fitted a diode-type second-battery-combiner at the alternator, it introduced hash (commutating noise from the diodes). Small capacitors across the diodes usually fixes this.
The aircon fan on my Pootrol is atrocious for AM noise.
If the noise is still present when the diesel is not running, well, hmmm.. Try running a small portable radio in the vicinity, tuning for the worst noise, and wandering around the car. You might find the source then. There may be some other item creating the hash when the Acc switch is on, but engine not running.
Gerry

From some experience with an allied issue (2 way HF radio for long distance comms) - all sorts of things (incl. the engine, fridges etc) can provide interference to AM - if it is local and strong, it will push the required incoming AM signal into the background - the further you go from the AM transmitter the worse the problem. Only thing is to kill the source of the interference where possible - we 2 way HF users often have to stop and turn the engine off to comm long distance. RE FM - a wholly different method of transmitting signals - unaffected by the stuff that ruins your AM signal (UHF 2 way radio ignores it too).

Also, most radios with AM have a trim pot on the chassis of the radio for setting up the antenna (usually variable between vehicles). The instructions on last one I had (a Pioneer) said to tune a station near a specific frequency (can't remember whether at the high or low end), then fine tune the antenna via the trim pot for best signal.

The one on my previous bike had the same setup.

This might be your problem. You'll need a flat blade jeweller's screwdriver of about 2.5mm to fit the trim pot.