[R-390] Antenna balun

[Todd, KA1KAQ]

On Wed, Jul 20, 2011 at 2:29 PM, Jim Haynes <jhhaynes at earthlink.net> wrote:

> And, one time in a surplus store, I found some things that had a twinax
> connector for the IBM network on one side, and a modular jack on the other
> side, and some kind of transformer in the middle.  I never measure the
> characteristics, but someone said the transformer is good for the
> HF range, and thus the thing makes a good balun for an R-390A.

I still have a couple dozen of these. Maybe 3-4 inches long, thick
black cable between RG-8 and -58 size. Never checked the balun in the
middle, guess I assumed it was more for keeping RF out than matching
anything.

Picked them up back in my mainframe days, which ended in 2008. They
were used with a number of AS-400 systems we had. The sad part is, I
missed getting a box of 50+ new connectors and the tool(s) required
for assembly, by a week or two. They were sent to the the gov't
surplus group who promptly threw them out (I checked, was too late
there also). But the AS-400 guys were great, pulling tiles and
locating maybe a dozen of the balun connectors they gave to me along
with another dozen or so they had left in their office.

The CU-286/FRR-33 uses 6-8 of them as well as the 390s and A. More
projects for the future.

BTW, the fellow auctioning the new baluns and ballast replacements is
or was a member of this list last I knew. Then again, that was a few
years back. I lost my very first 3TF7 as few months ago. Fortunately I
have spares, but the good ol 47 ohm/5-10watt resistor makes a fine
replacement.

de Todd/'Boomer'  KA1KAQ/4