Topband: Noise cancelling

[Thomas Damboldt]

Hi Garry,

what you are saying is not true. The MFJ-1025 noise canceller does not "noise cancelling" but "beam forming". The two antennas (one MAIN and one AUXILIARY) are used by gain and phase adjustment to form a 2 element beam, where the diagram is a cardiod, i.e. is has a null in a variable direction. This is useful to null out an interfering (ground-wave) signal which can either be noise or an interfering station. The nulling occurs by putting the signal into the null of the diagram. The MFJ-1025 does NOT "cancel the offending noise" as your mail suggests.

73
Thomas, DJ5DT
14. Feb. 2004


"Garry Shapiro" <garry at ni6t.com> wrote:
> It is precisely that situation in which cancellation can work. The idea is
> to have a noise antenna that picks up the local garbage but not the desired
> signal, and use that signal to partially cancel the offending noise. A small
> loop or a low doublet can do this very well.
> 
> Garry, NI6T
> 
> 
> 
> Hi,
> 
> it seems we have the same problem in all large cities. To my understanding
> the noise is caused by large numbers of halogen lamps, dimmers and other
> kinds of electronic equipment and is radiated from the extensive powerline
> network all over the place. This means that even directive antennas (flags,
> pennnants etc.) will not help as the noise is probably omnidirectional. It
> would be helpful, however, to use a small receiving antenna (e.g. a loop)
> and just try to find a "quiet spot" in the area accessible.
> 
> Best regards
> Thomas, DJ5DT
> 13 Feb. 2004
>