Mike, I don't know about loading coils but I guess it's possible 
they did.  They also made a 4 element quad called the Moon Raker.  
I don't remember if the company was called Uni-quad or what the 
brand was but the one I got had a good front to back ratio and 
changing polarity really helped bring in, or null out signals 
depending on a number of variables.  The antenna was light, only 
requiring a tv rotor.  73, Jim WA6EKS

 ----- Original Message -----
From: "Mike Duke, K5XU" <[log in to unmask]
To: [log in to unmask]
Date sent: Sat, 22 Aug 2015 21:20:34 -0400
Subject: Re: The PDL CB Quad

Jim, the PDL quad that you mentioned was the first CB quad 
antenna I
ever encountered.  If memory serves correctly, they had some 
loading
coils in each element, which made them less than full size.
Nevertheless, they did play quite well.

A friend, and later my brother also, had the Hy-Gain CB quad.  It 
was 4
elements on a 24 foot boom, and was called the Big Gun.  It had a 
signal
that lived up to its name.

--
Mike Duke, K5XU