Yes, it is balanced on Bands 3 and 4 above 5.3 MHz. But the two coils
for the lower bands have no primary windings and terminal A1 connects to
the top of the coil for either Band 1 or 2. When the switch S1A
connects to either 1 or 2, the two primary windings for 3 and 4, as well
as terminal A2, are left floating. My measurements of my S-40B confirm
this.
Note that this is only for the S-40B and S-85 and is completely
different from the S-40A.
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On 2/10/25 12:34, Richard Knoppow via groups.io wrote:
It is a balanced imput. Redraw the input circuits to show the actual
wiring without the switch.
On 2/10/2025 11:26 AM, Maynard Wright via groups.io wrote:
It would be difficult to rewire the S-40B to allow balanced input on
Bands 1 and 2. The S-40A uses transformers with primary and secondary
windings and resonance of the secondaries on all four bands. The S-40B
does that same thing for Bands 3 and 4 but connects antenna terminal A1
directly to the "hot" end of each resonant coil for Bands 1 and 2, with
a series 1000 ohm resistor between A1 and the coil for Band 1. So there
are no primary windings for Bands 1 and 2.
If someone really wants a balanced input below 5.3 MHz with an S-40B or
S-85, it might be useful to wind a 1:1 input transformer to place
between the receiver and the transmission line.
73,
Maynard
W6PAP
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
