Topband: to rotate or not to rotate

[Tom Rauch]

Hi Lane,
 
> Is worth the hassle to be able to rotate the 5' per side shielded loop for
> 160 rcv? Putting it together right now and have a chance to put a rotor on
> it next week.

Not unless you have a well defined local noise or signal source, or 
coupling to a nearby object that is re-radiating noise or undesired 
signals.

The nulls on a small loop are so sharp that nulling skywave is 
virtually impossible (except under ideal conditions, and even then it 
almost always requires tilting the antenna as well as turning).

> Also, does height above matter with this thing? Should it be higher than=
> the roof of the house?

Height makes little difference, but distance to noise sources or 
finding a dead spot for local noise can make a large difference. The 
roof might be a sweet spot, or a sour spot, to put the antenna.

By the way, in a "shielded loop" the shield is actually the antenna.  
Like all antennas it responds to both electric and magnetic fields. 
Very close by, the small loop's field response is magnetic field 
dominant. About 1/10th of a wavelength away the response of a 
small loop actually becomes electric field dominant! In the far field 
all antennas have the same in field impedance.


73, Tom W8JI
w8ji@contesting.com



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