[ARC5] " ARC-5 " Transmitter Antenna Matching.

[Mike Hanz]

zeno wrote:

> I looked this up. It is (chapter 19.16/ Transmission Lines) in my ARRL 
> handbook. In figure 19.14 they show a "4::1 Balanced to Balanced 
> current transformer wound on two cores, which are separated. Use 12 
> bifilar turns of #14 enameled wire wound on FT240-43 cores for A and 
> B. Distribute bifilar turns evenly around core."
>
> OK, sounds do-able. Where do you get these FGT240-43  cores, is this 
> something readily available? They only show an abstract illustration. 
> As a beginning do-it-yourself hobbyist a step by step photo would be 
> nice, but I will have to use my imagination as my elmer....


Let's be clear on this.  An unun is */not/* required to get a command 
transmitter on the air.  The series cap /*is*/ generally a requirement, 
however - either Marty's receiver variable or the fixed cap that Dave 
suggested.  The wide variety of most of our ham antennas recommends 
using the variable, at least as the first step or if you're not sure of 
its characteristics at the feed point.  The unun is one of those things 
you might want to try as a second step after you've had fun operating 
the set for a while.  The thrust of my note was simply why it might be 
considered as a reasonable optimization step.  There is another aspect 
which I forgot to mention, and that is if you house both the unun and 
series cap in an old aircraft box of some sort and paint it black 
wrinkle, it makes both a professional looking transition from open wire 
to coax and lends an authentic look to the rig.   At any rate, the 
easiest method to build one is to wind it as an autotransformer.  There 
are several sites that cover building ununs.  One of them that has a 
number of additional links is:

http://users.netonecom.net/~swordman/Radio/unun.htm

There are others you can find with a google search, but this is a good one

http://www.amidoncorp.com/product.htm is where most of us get cores...

73,
Mike