It was a beautiful day here in Northeast Missouri, or so I've been told. I
spent the day in the basement workshop winding coils for receive antennas.
Tommy, WD4K is experimenting with some Pennants, and asked me to wind him up
a couple of transformers.
The small cores that I normally use weren't big enough for the large number
of quadrafillar turns needed to match 75 Ohms to 900 Ohms, so I took the
advice of Mauri, I4JMY, and went to a much larger core, and a smaller number
of turns but with larger wire. Well with the FT-140 J's that were on hand
1.4" dia x .9" tall and u=5000), Mauri's recommendations were darned close.
I wound up liking a 3T primary and a 7T secondary for the 50 to 470 Ohm Bev
transformers and 3T/11T for the 75/900 for the Pennant. Both worked well on
the lashed up test setup that I threw together this morning.
With the smaller turns count working so well, I went back to the smaller
cores for Tommys units (FT-50-75's) and had plenty of room to spare. That's
his in the glue drying fixture on the left of the '259 in the photo.
You can also see some of the jigs that make the cut and try method a little
easier.
The colored wire looks nice on the black cores. One unit is wound with black
wire on a black core, but I can't seem to locate it. Maybe for Christmas
I'll give my wife a nice big red core with green wire on it and see if
she'll hang it on the tree.
One final comment : don't think for a minute that the workbench always looks
this way. No, it's usually a mess, but I cleaned it up for the photo.
testsetup wide view:
http://homepages.dstream.net/K0FF/160/BevBox/Testsetupwide.jpeg
Closeup
http://homepages.dstream.net/K0FF/160/BevBox/TestsetupClose.jpeg
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