[R-390] antennas

[Jon Schlegel]

Hi All,

Check this out.

http://cgi.ebay.com/r-390-adapter-matching-ant-bal-to-50-ohm-unbal_W0QQitemZ140168831515QQihZ004QQcategoryZ4673QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

The label seems to show an unbalanced connection to BOTH twinax 
pins.  The termination resistor seems to suggest that the source 
might otherwise see an impedance that would be much greater than 50 
ohms.  Could this be a fixture to adjust for best balance on a 
receiver's input?

Regards,
Jon Schlegel
WA3MVM


At 09:19 PM 10/17/2007 -0700, you wrote:

>On the 390's we used on the Navy ships I was on, there was a
>connector (right angle) which took the two pins of the balanced
>input, shorted one side to gnd, and the other side to the center
>pin of a "C" connector, where most often, it was connected to
>a 35 foot vertical whip, fed either direct or through an antenna
>splitter.
>
>Don't know the splitter name - it divided the signal into bands,
>2-4, 4-8, 8-16, 16-30, or something similiar, and had about
>4 outputs for each freq range.
>
>John
>
>At 06:31 AM 10/17/2007, Rasputin Novgorod wrote:
>>Hi Guys:
>>
>>My random wire connects via a 9:1 un-balun to 50 ohm coax.
>>The shield is grounded. Because I had the correct adaptor,
>>I connected the coax to "Unbalanced" antenna connector on
>>the R-390A. It works well.
>>
>>But as I skim the schematics, it appears that the unbalanced
>>antenna connector goes to the secondary side of the input
>>preselector(?) CL filters. Does that mean I miss out in the
>>first layer of filtering?
>>
>>The "Balanced" connection goes to the Primary side the
>>"preselector". Would I be better off connecting there?
>>I know some people connect an unbalanced antenna to the left
>>pin of the "balanced" connector and ground the right pin.
>>
>>In the good old days, how would the military connect the
>>Balanced connector to a dipole? Would they have some
>>sort of 125 ohm dual conductor coax? Surely not
>>ladderline.
>>
>>Perhaps instead of answering my questions, someone can tell
>>me what I need to know...
>>
>>Sincerely,
>>/blair
>>
>>
>>
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