Wednesday, March 5, 2014

New Cores for the RF MIxer

After building my Farhan Minima RF Mixer, and before taking it to Jack's LAB for performance evaluation, I replaced the two large cores with much smaller BN-43-2402 binocular cores. I had originally planned to use the smaller cores but I could not find my roll of very small wire with which to wind them, and therefor the first configuration sported the larger cores wound with 22 AWG wire-wrap wire. The RF Mixer worked, but . . .

Old Large BN-43-302 Cores
The new smaller cores fit the board much better, and they have also worked well on my BFO SSB Modulator/Detector board as well.

New Small BN-43-2402 Cores
as Original Planned
The small cores with the small wire are more difficult to wind, but with patience it can be done. The circuit requires eight turns of trifilar wire. With the small wire that I have (I do not know the gauge) only eight trifilar turns will fit (the circuit requirements are met).

One neat trick that I learned (in the distant past); before winding a DIY bifilar or trifilar wire together, stain one (or more) full length wires with colored Marks-a-Lot pen(s). The enameled magnetic wire takes stain reasonable well. A large felt tip pen and a slightly stretched (taught) wire makes the task easy. After twisting the wires and winding the cores, the stain will help make end identification much easier.

If I remember correctly, pre-stained filer wire is available for purchase, but I like DIY colored stained trifilar wire, because I can use any gauge of wire that I have available.

Based on the online Toroid Calculator, I may have only needed 4 turns on the BN-43-2402 Binocular Cores.

I had previously mis-published the part number of the Binocular Cores that I am using, the number and links have been corrected.

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