Re: [IRCA] IRCA Digest, Vol 41, Issue 116

["Rob Moore" <rmoore5@xxxxxxxxxxxxx>]

Hi Craig,

The ALA-100's which are used in the Wellbrook array are active antennas.
Each has a preamp which is located at the bottom of the loop and has I
believe around 16db of gain.  They are also very quiet, push-pull Norton
noiseless feedback amps, I believe, so the quality is quite high and they
are very low noise.  I'm not sure how this will affect noise leakage into
the cables but Andy at Wellbrook  or John Bryant might help.

>From their website and reading what Guy Atkins has to say, there are two
loops in the array and they are set up 40 meters apart.  I think Wellbrook
is also considering a 4 loop array but I haven't heard anything definite
about it.

Rob Moore

-----------------

Date: Mon, 17 Sep 2007 07:55:29 -0400
From: "Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>
Subject: Re: [IRCA] Phasing /RF notch, etc.
To: "Mailing list for the International Radio Club of America"
	<irca@xxxxxxxxxxxxxxxx>
Message-ID: <014a01c7f921$acfce3c0$3c32a8c0@ng1u>
Content-Type: text/plain;	charset="iso-8859-1"

> I don't give up that easily. The Wellbrook Array sounds like it does
> have some good directional properties.

I do have some questions about the array that the Wellbrook site is unclear
on.  It apparently uses four loops.  How are they set?  So all four line up
in the same direction?  That would seem to work, as the inherent null of the
loops would minimize side-to-side pickup, and the phasing would null other
directions.

I have been working on a similar arrangement, but using either copper tube
loops or two of the large ferrite bar antennas.  Set them up so they null to
the sides of the desired direction, then phase them for a null towards the
rear.  Computer simulations show a very nice and tight pattern.

The problem I have been having is the leakage into the coax, per previous
messages.

I wonder how Wellbrook avoids that?  Some significant amp in the loop
itself?  How are they connected?  Just coax?  Any special isolation
techniques?  Maybe amplifying the signal way up and then attenuating it (and
the leakage) way down again?


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