[R-390] Differences between the balanced antenna and unbalanced antenna inputs

[David Wise]

I used to think that, but not anymore.  The unbalanced input is meant to be used with an antenna with a specific capacitance, which acts as part of the capacitance that resonates the secondary winding of whichever transformer is selected for your band.  The primary winding that the unbalanced input skips is nonresonant.  The caps there don't resonate, they just establish a center tap for balance.  You get the same number of tuned circuits either way.

Dave Wise
SWL (inactive)

________________________________
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Tisha Hayes <tisha.hayes at gmail.com>
Sent: Sunday, November 3, 2024 10:44 AM
To: R390A <r-390 at mailman.qth.net>
Subject: [R-390] Differences between the balanced antenna and unbalanced antenna inputs

There is one advantage of using the 125 ohm balanced antenna inputs; You
get a little bit more pre-selection through RF transformers T201 to T206.

When using the 50 ohm unbalanced connector (the C connector) it bypasses
those RF transformers.

You can see this on diagram 5-14

*Ms. Tisha Hayes, AA4HA*

*Senior RF engineer (4RF USA, retired)*
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