Topband: MFJ 1025

[Raoul Coetzee]

Tom wrote:

>Noise often has a high ratio of peak to average power, S
>meters don't always follow noise levels well for sharp noise
>spikes with wide spacing. This is especially true when DSP
>systems with wide IF stage filtering are involved since they
>overload (not enough bits or speed to maintain pulse shape).

>There was a fellow on the RFI reflector who was puzzled why,
>when he switched in an attenuator, his S meter didn't show
>noise dropping at the same rate as desired signals. His
>noise dropped faster than the signal. This meant he could
>use an attenuator and improve S/N ratio. After some emails
>between us he tried a receiver that used crystal IF filters
>instead of  a DSP for primary selectivity and everything
>behaved normally.

This brings me to a question about the FT1000 MP MK V Field that I am using:

Last season I found that using the DSP noise reduction and the 250Hz crystal
filter from Yaesu gave best signal to noise.
(or using the narrowest setting of the DSP filter with the 250 hz crystal
filter in the IF.)The  500Hz 455KC mechanical filter Collins that I also
installed is hardly used on 160m.
It seems as if it is a case of VERY narrow or WIDE open.
This season on 160m I always use the widest settings for best copy! The
noise seems to the same (qrn noise)Could it be that I have new local noise?
BTW I also use the attenuator a lot. Antennas are the same as last season.
73
Raoul