Presented here are several ways to incorporate automatic switching with the AADE DFD2.
The first one, Switching the DFD2 with the Switches on the PCB, interfaces with the band switches on Board 1. Parts for this method are included in the Frequency Counter kit.
There are several ways to hook up rotary switching for the receiver and for both the receiver and the AADE DFD2. The easiest one is to use a 2 pole rotary with at least 4 positions, check out AADE DFD2 and Receiver Switching with 2 Sections. No rotary switches are included with the kit.
The first rotary schematic is for receiver switching only.
For those using the SWL version of the receiver, a three section rotary switch is used for switching the bands. Manual switching of the bands is shown in the SWL instructions.
NOTE: This is a revised schematic (date: 1/14/07). All customers who have CDROMs dated between 9/20/06 to 1/14/07 need to update with this schematic.
The base connections for the transistors have been moved from the left side of D4 and D5 to the right side between D4/D6 and D5/D7.
NOTE: D1, D2 and D3 are very important diodes and should be double checked for proper position (band away from counter) before connecting the switching circuit. These diodes protect the frequency counter PIC from 12 Volts coming from the receiver board.
If a wiring mistake was made, a transistor was bad, or any other reason, the PIC would be blown up having 12 volts on its offset pins.
D6 and D7 keep 5 volts from the counter from getting into the switching circuit of the filters and partially turning on an LED that is supposed to be off. They isolate the counter 5 volts from Board 1. If a mistake is made here, no damage is done.
The wires going to the switches from the 20/17 and 30/17 circles at the Bandpass and Crystal Filter on Board 1 are disconnected at the switches and soldered to the points labeled 20/17 Circle and 30/17 Circle on the schematic above.
There are no connections between the circles and the switches on Board 1 anymore.
The 20/17, 30/17 and 40/30 Switch labels go to the switches at the front of Board 1 in the holes labeled as noted.
This circuit is built "ground plane" style with high megohm resistors used as standoffs. You could also use a small piece of prototype printed circuit board.
This circuit is a very slow on-off switch so any type of diode and any general purpose NPN transistor can be used.
The picture above shows the switching circuit "ground plane" style soldered to the frequency counter and Board 1..
Watch out for the correct connections from the Bandpass and Crystal Filter connections. See below.
A wider view of how it all is connected.
The switches on the board can be removed if the rotary switch is used.
The rotary switch has been mounted on Board 1 with two standoffs. The space between the standoffs just accepts a standard size rotary switch.
Notice the wiring to the switch and the connections on the board.
Another place to mount the rotary is on a piece of PCB board soldered to the bottom plate.
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The receiver has its own rotary section and the frequency counter has its own rotary section.
Some rotary switches have two sections on one wafer. These might be cheaper than a rotary with two wafers. Also, almost all now have more than four poles, i.e. 11, and are sold as universal rotary switches. They will work fine, just use four poles.
Remember to use an RF Choke and .01 bypass capacitor at the jumper connections of the Frequency Counter when hooking up the counter section. See picture.
Thanks go to James Wallace of Rowle