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8640Jr Divider Chain


8640Jr Divider Chain

The VFO of the 8640Jr runs from about 13.5 Mhz to about 31 Mhz. This frequency is run through a couple of dividers to yield a couple more bands.

The divide by 2 band runs from about 6.75 Mhz to about 15.5 Mhz.

This output is then divided again to yield a band from about 3.375 Mhz to about 7.75 Mhz.

That is where the original design left off. I wanted to be able to at least cover the 160 meter band, so I added another chip and did two more divisions.

So I have an additional band at 1.6875 Mhz to about 3.875 Mhz, and a final band at 834 khz to 1.9375 Mhz.

Here is what the divider board looks like…

8640Jr Divider Chain

The circuit was built on an old Radio Shack prototyping board that I had in my junkbox. The back side has some traces to ease the development process. That unsoldered connection in the upper right of the photo came back and bit me later, after I had soldered the board into the die-cast box. So I had to unsolder the power leads and all 5 bnc connectors from the board to remove it and fix the problem.

Bottom of 8640Jr Divider Chain

I boxed it up in a cast aluminum box, and sent the outputs through BNC connectors to the low pass filters.

8640Jr Divider Chain in enclosure

Once it was all working, I buttoned it up.

8640Jr Divider Chain Buttoned Up

Here is the Divide by 2 output at about 6.9 mhz…

Divide by 2 Output ~ 6.9 mhz

And the Divide by 4 output is at about 3.44 mhz…

Divide by 4 output ~ 3.44 mhz

And the Divide by 8 output is at about 1.72 mhz…

Divide by 8 output ~ 1.72 mhz

Finally, the Divide by 16 output is at about 862 khz…

Divide by 16 output ~ 862 khz

These outputs are all fed into a low pass filter for each band. I am starting to lay out those next…


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