Re: [IRCA] QST article

[markwa1ion@xxxxxxx]

What I would do is use 9:1 transformers at each corner and run two 
balanced feeders (Z ~ 100 ohms) back to the shack.  These would be 
ordinary AC zip cord or dual-conductor #16 stranded speaker wire.

At the shack, use a 2:1 transformer on the line going to the receiver 
50 ohm unbalanced and run the other to a 500 ohm pot.  Adjust pot for 
null.  I would make a switchbox so you could swap the receiver and 
termination lines.  This is basically what was done last year on the 
SuperLoop at Marc DeLorenzo's in Dennis, MA.

This set-up isolates the antenna from noise and stray pick-up better 
than the coax feed method.

Mark Connelly, WA1ION

-----Original Message-----
From: Craig Healy <bubba@xxxxxxxxxxxxxxxxxxxx>
To: badx@xxxxxxxxxxxxxx; Mailing list for the International Radio Club 
of America <irca@xxxxxxxxxxxxxxxx>
Sent: Sat, 15 Nov 2008 10:12 am
Subject: QST article



The current QST has an interesting article on adding a loop antenna on a
tower.  A 2m beam was used as a horizontal support and the rotor mast
extended up above the beam.  Insulators were tied to the ends of the 
beam.
Wire was run horizontally above the beam through the insulators and up 
to
the top of the PVC pipe used as the mast extension.  The loop is a
triangular shape.  In this particular arrangement, the feed was done by
splitting the wire in the bottom center.  No transformer was used, and 
the
coax connected directly to the split.  A 910 ohm resistor was inserted 
at
one of the lower end corners.  Ground side of the coax was toward the 
end
with the resistor.

Operationally it had good pickup and overall had lower noise.  Rotation
nulled some noise sources.

It might be interesting to put transformer pickups in each of the lower
corners and run two identical coax feeds down so it could be phased.  
Dual
RG6 coax would be perfect for that.

In the same QST is a review of the Perseus SDR.

Craig Healy
Providence, RI



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