[R-390] Antenna balun

[Dennis Wade]

I've found these twinax/modular connector things as well.  I destroyed
one and used the twinax pigtail to connect a homemade balun to the
'390A.

My connection from the pigtail to the pc board I mounted the balun on
was the weak point in the assembly, as was my lack of onfidence in the
characteristics of the balun I wound since I don't have the equipment
to properly analyze it.  I don't think it was as completely shielded
as it should have been.

I've also seen parts similar to the Mini Circuits device mentioned
above, but in looking at the data sheet its not obvious (to me anyway)
how to connect it up correctly.

                Dennis

On Wed, Jul 20, 2011 at 11:29 AM, Jim Haynes <jhhaynes at earthlink.net> wrote:
> On Wed, 20 Jul 2011, Tisha Hayes wrote:
>
>> Finding the coax and connectors is pretty easy. It is the same stuff that
>> was used on IBM ThickNet connections in the bad 'ol mainframe days. Looking
>> for it as a radio supply will not yield any results or will show folks who
>> know that it can be used for the R-390/A and they charge an arm and a leg
>> for it. Surplus IT places will practically beg you to take it away.
>>
> 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.
>
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-- 
"If they trust you, it is an extraordinary privilege, and you simply
can't abuse it."
      - A. Alan Post  1914-2011.  California Legislative Analyst 1949-1977.

-------------------------
Dennis L. Wade
KG6ZI
Carmichael, CA