[R-390] Balances Antenna Connector

[Bob Camp]

Hi

So, if you head back to par. 3.13.3 in the “official spec” previously mentioned:

From 500 kc to 16 mc they call out a > 50 ohm / < 375 ohm input impedance for the radio.

For the 16 to 32 mc range that goes up to > 100 ohms / < 700 ohms. 

You could look at those numbers a lot of ways. One way would be to see what the mid point is:

(50 + 375) / 2 = 212.5 ohms

(100 + 700) / 2 = 400 ohms

Without real data over each range there is no way to justify those as the actual “average impedance” over the range. Still, it’s what we have right now.

If you are worrying about weak signals (rather than overload), the high range is the thing to target. A 400 ohm transformer just might be the one you would want.  

Bob

> On Oct 10, 2024, at 4:23 PM, Tom Frobase <tfrobase at gmail.com> wrote:
> 
> Here is a link to some 4:1 Baluns.  I use them to make Balance antenna
> adaptors.  The 4 side to the two twinax pins, the 1 side to a BNC input.  I
> drill out the back of the Twinax Connector to fit a 3/8" chassis mount BNC
> socket.  I fasten it in place with a small allen set screw.  The Baun is
> glued insideThey work very well.
> 
> https://www.ebay.com/itm/265016480357
> 
> ... tom, N3LLL
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