making a DBM

I put a DBM together last night and did some testing. The core is as the previous test indicated. 10 turns = 100 uh. My test indicated a 10 to one VFO to signal ratio to produce the best results. example 500 mv LO and 50 mv RF produces 10 mv IF. I plan to do another with more inductance and see how it effects the operation. I'm posting the construction.

I cut 3 wires to the same length and wrap them together.

The wrapped cores with 3 coils .

Separate the wires and prepare to clean the varnish from them.

The wire can be soldered without stripping the varnish. The varnish will burn off IF you get the wire hot. I put a drop of solder on the bare end and work down it. You can also use a small flame to burn the varnish off. An alcohol lamp is ideal for this but a torch work too. After heating removing the soot and ash with an alcohol wipe works well. I heard of a guy using a small cup of alcohol to dip the wire in. After setting it on fire he turned it over then things went bad. The wipes are safer.

Use the ohmmeter to find a coil, this will be the primary twist it to ID it. Find another coil. Connect one end of it to the other end of the remaining coil.

Make a pin board with the layout for a diode diamond and the I/O. A piece of perf board might be better if you have some.Run a ground lead from LO and RF inputs. Connect the primaries and center taps of the secondary.

The remaining wires go to opposite sides of the diamond. Now all that's left is mounting the diodes.

I use clip leads as heat sinks. Pair the head and tail of a pair of diodes and connect them to a pin. Pair the other diodes head to tail and connect them to the opposite corner.

Take a head and tail and attach them to a corner.

connect the remaining ends to the last pin.

The finished product. This works well for a test bed to try the cores. The final product will probably be put in a metal box. You can attach the cores to a ground plane by soldering the ground connections to it. Then use the 4 leads that connect to the diodes as stand offs to solder the diodes to.

I'm feeding it a 4001KHz @ 500mv and 4000KHz @ 54mv  signal and getting a 1KHz @ 5mv output. (best I can remember. I should have wrote it down. I took pictures of the setup but can't read them.) Anyway it works it is not sensitive enough. I will try more turns on the coils.