This information is an untested circuit submitted by Don W6QS

Transmit mode (from Ethernet to RF): => Assume Vc (Rx driving signal) = 0

Vd= 25 * I_ethernet (Note: the 25 ohms is the parallel impedance of R5 and R6)

Ve = Vd * (1+R8/R7) = 2*Vd

Assume that Va (the received signal) is the same magnitude and phase as Ve (the received signal caused by the modulation of the gunplexer is the same as what it transmitted)

==> assume Va=Ve

Vb= R2/(R1+R2) * Va = Va/2

Vc = Vb*(1+R4/R3) - Ve*(R4/R3) = 2Vb - Ve = 2*(Va/2) - Ve = Va - Ve

But if Va = Ve

Vc = Ve - Ve = 0 (which was the original assumption)

===> none of the transmitted signal gets back to the Vc node and thus back to the ethernet card.

Receive mode: ==> Assume Ve (modulation signal) = 0

Vb = Va (R2/(R1+R2) = Va/2

Vc = Vb (1+R4/R3) = 2Vb = 2* (Va/2) = Va

Vd = Vc * R6/(R5+R6) = Vc/2 (valid with the transmission line terminated with its impedance)

Ve = Vd*(1+R8/R7) - Vc*(R8/R7) = 2*Vd - Vc = 2*(Vc/2) - Vc = Vc - Vc = 0

===> initial assumption proved - none of the received signal gets back to the modulation input

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