Work is progressing nicely as we have some of the major components mounted on our PC Board and we have completed the Simulation of the Band Pass Coupler that sits between the 12DQ7 and the 12GE5.
We also have a first draft of the No Tune Output Network simulation that mates the 12GE5 with the antenna. This may be a bust but I see it as having a good chance of working. Impedance matching is key.
Adding Parts to the Transmit Board
On the left is the 12DQ7 in a shielded socket, where below that will be the Band Pass Coupler. The RF from the lower level stages is fed just behind the 12DQ7. A shield is planned between the two stages. In the center is the Bias Pot.
Now I am planning ahead should a Pi Network be needed and that Bias Pot bracket becomes one anchor point for a front panel which would house the Tune Cap which would be to the right of the 12GE5. Immediately you can see the why of the 12GE5 -- no exposed High Voltage on a Plate Cap. Behind the 12GE5 is a 4PDT relay for various control functions including antenna switching.
The following is the simulation of the output coupling network and the incorporation of the W3NQN LPF.
The cutoff frequency is slightly greater than 8 MHz and the second harmonic suppression is greater than -130dB.
Them That Know Can Make It Go!
73's
Pete N6QW