The fitted radio, thanks to my skinflint boss is a "bare minimum"
Mercedes branded unit, actually made by Becker, I believe. It is
therefore a good quality, if basic, piece of kit. The antenna is I
guess from the same "box" ie standard quality etc. FM reception, for
instance is OK. All the truck electrics, including the radio are 24V,
albeit from 2 X 12V batteries in series. The built in unit is JUST
tolerable on AM when there is a really good signal ie in the UK, if
the signal is at all weak (I am guessing here), other noise dominates
ie a rhythmic low frequency "fart" noise, (I guess this comes from the
tachograph, stupidly fitted next to the radio) A whine, related to
engine revs (alternator?? fuel pump??) horrible noises whenever I pass
under a bridge or anywhere near power pylons or railway lines.

The portable radio (with its own batteries 8 X D size = £24.00 or
approx $40.00 the set) has markedly better Rx even when just outside
the cab, on the step for instance, and strangely seems not to be as
badly affected by the bridges and pylons

On Thu, 18 Aug 2005 07:59:22 -0400, "J. Mc Laughlin"
wrote:

Dear Mr. Stephen Parry:
It is possible that the truck (it is one truck?) produces too much noise
at 198 kHz. An important test is to note if your portable radio tuned to
198 kHz receives a satisfactory signal-to-noise ratio when the truck is
running all of its equipment. Try placing the portable radio next to the
truck in places where one might attach an antenna.

The fitted radio, which has LW, must have an outside antenna. Is that
antenna in good condition?

Your solution might be to reduce the noise produced by the truck.
Antennas for LW suitable for mounting on a truck do exist, however they will
not help if they receive too much noise.

Could describe one of these please??

Let the group know the results of your testing. Tell us more about the
truck. Regards, Mac