Re: [IRCA] Array Solutions SAL-30

[Mark Connelly <markwa1ion@xxxxxxx>]

Two active whips can be phased successfully if they are about 40-60m 
(130-200 ft.) apart.

Nulls of stations along the axis can result in a cardioid pattern.  
That means that if one vertical is due west of the other, you can 
develop a null due west or due east with a peak in the opposite 
direction.  Sides (north, south) will be about 5 dB down from peak.  If 
the stations to be nulled with the east-west verticals are north or 
south, there is no arrival time difference in that case, so phasing to 
produce a null north also produces a null south, i.e. you get a 
figure-of-eight pattern with maxima east and west.

If the whips are much closer to each other than about 20m / 65 ft., you 
will tend to null everything at once especially on the lower end of the 
dial.

1/12 to 1/3 wavelength spacing is a good rule-of-thumb.  1/12 
wavelength at 500 kHz works out to be 1/3 wavelength at 2 MHz so that 
spacing (50m / 164 ft.) is just about ideal for MW.  I had good results 
on tests at the Rowley, MA salt-marsh site with phasing of two active 
whips at 50m spacing on an east-west axis.  Arrays for shortwave can, 
of course, be spaced more closely.

I'm not sure what spread you presently have between those whips.  
Hopefully this information will be helpful.

Mark Connelly, WA1ION
South Yarmouth, MA

<<
Nick,

I'm glad that you addressed this topic. I've experienced a similar 
issue
when phasing active whips against each other. Deep nulls are easy 
enough
to obtain, using the Quantum Phaser with 2 LF Engineering Active Whips,
but once nulled, the remaining signal is so low that identification of
stations underneath can prove impossible.

What is the solution to this problem? It sounds like you're saying that
bigger antennas with a greater capture area may be the only solution?
Unfortunately, that's not a great option for my deed-restricted, HOA
situation or my small back yard in general.

Any suggestions welcome. Thank you for sharing your expertise. Very
helpful to a newcomer.

--
73,


Les Rayburn, N1LF
Maylene, AL
EM63

Member NRC, IRCA, & Medium Wave DX Circle
Former CPC Chairman for NRC/IRCA

SDR-IQ,Funcube Pro, Wellbrooke ALA-1530+ loop, LF Engineering Active 
Whips,
Quantum Phaser, Kiwa Loop, Palstar MW Pre-Selector
> >

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