ANTENTOP- 01- 2016 # 020

Experimenters with Non Snap Ferrite Cylinder Bead RF Chokes

Well, but what can I do with old Ferrite "Bead" RF Chokes. I just cut of the chokes together with wires from scrapped devices. To remove the ferrite tube from the chokes takes time and tools. So I decided make some experimenters with the chokes without disassembly those ones.

I find in my junk box four identical Ferrite "Bead" RF Chokes. Each choke has length 36- mm with outer diameter 18- mm. Two wires cable went through the choke. The wire was marked as diameter 18- AWG and 300- V voltage. My idea was to create a kind of RF transformer with the chokes.

First experimental transformer was made according Figure 4. It was classical RF Transformer where one turn is primary and second turn is the secondary winding. Then transformer was tested. Primary winding was connected to MFJ- 259B. Secondary winding was loaded on to 51- Ohm resistor.

Figure 5 shows the transformer loaded to 51-Ohm resistor. Table 1 shows data obtained for the one Ferrite RF Choke. As you can see from the table the transformer may be used for receiving purposes. I tested the transformer with my transceiver IC- 718 and receiver Hallicrafters S- 85. Transformer worked good up to 40- meter Band. Then I observed some dropping of receiving signals. However I could compensate it with adding RF- gain at transceiver and receiver where the transformer successfully worked at MW-Band.

Conclusion: The transformer may be used as Insulated Transformer for Receiver at the HF and MW.

Figure 3 Snap Ferrite Choke on the Coaxial Cable

Table 1 One Cylinder Ferrite RF Choke loaded to 51- Ohm Resistor. Data obtained with MFJ- 259B

Figure 4 RF Schematic for Transformer on one Ferrite RF Choke

Figure 5 RF Transformer on one Ferrite RF Choke loaded to 51- Ohm Resistor

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