[Lf] [Fwd: LF: A small question of size]

[Andre' Kesteloot]

vernall wrote:

> john sexton wrote:
> >
> > Hi Bob,
> >
> > I am glad you pointed that out, so much for theoretical formulae, I was just
> > about to embark on a much larger receiving loop. My current one is about 1
> > metre in diameter. It outperforms the vertical, just because the noise is so
> > much less. However I have noticed that when I connect the vertical to the
> > Tx, there appears to be a lot of coupling between the two antennas, and the
> > noise level goes up from the loop.
> >
> > Vy 73, John, G4CNN
>
> Similar at my QTH.  For LF receiving I usually use an active whip sited
> at the back fence of my property (for maximum separation from houses).
> When my nearby toploaded (transmitting) vertical is connected the
> neighbourhood noise rises about 20 dB.  The neighbourhood noise is
> mostly clicks, pops and PSU hash that I assume is transported on the
> power mains.  On receive, I not only have the transmitter off, but I
> also need to "float" the transmitting antenna.  This is an example of
> the larger near field of the larger vertical leading to generally worse
> results for receiving than using a smaller but well-sited antenna.
>
> Straying a little off the topic: it is also important to have a well
> isolated power supply and common mode choke on every connection to a
> remote receiving antenna, otherwise the dreaded mains noise will sneak
> in to the system.  Balanced RF feeders with transformer coupling at each
> end is probably the simplest technique that can deliver good results.
>
> 73, Bob ZL2CA