Band 2: 4-8 MHz Introduction

General

The latest design of the HF-BPF kit now permits of two options:

• Option 1: the original design covering 1.8 MHz - 30 mHz, in 4 bands, and
• Option 2: a board covering 3.5 MHz - 30 MHz plus 6m, in 4 bands

These builders notes describe 4 "bands" and the board layout permits filters for four bands. However, depending upon the option (1 or 2), the bands named "band 1" and "band 2" will be built and installed differently. The changes for Band 2 are as follows (and will be implmented somewhat more elegantly in these note, time and resources permitting):

• Band 2 is changed between option 1 (4-8 MHz) and option 2 (3.5-8MHz):
  • C10: option 1=100 pF; option 2 = 120 pF
  • C11: option 1=390 pF ; option 2 = 270 pF
  • C12: option 1=100 pF ; option 2 = 120 pF
  • L4: unchanged
  • L5: option 1= 2.1 uH ; option 2 = 3.5 uH
  • L6: unchanged

See the detailed techniques for winding toroidial coils

Theory of Operation

This stage builds and installs the filter "chain" for Band 2. Refer to Jan G0BBL's Design Plots to see the performance characteristics of this chain.

Remember, when winding toroidal inductors, a single pass through the core counts as 1 turn. You might want to review Leonard KC0WOX's excellent 10-minute video on winding toroidal coils.

(go directly to build notes)

Band 2: 4-8 MHz Schematic

(Resistor testpoints (hairpin, top, or left-hand lead), as physically installed on the board, are marked in the schematic with red dots)

(Click for Full Schematic)
(go directly to build notes)

Band 2: 4-8 MHz Bill of Materials

Stage Bill of Materials

(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)

Check	Designation	Component	Marking	Category	Orientation	Notes	Circuit
❏	L4-core	T25-2 toroid core	red	Toroid			Band 2: 4-8 MHz
❏	L5-core	T25-2 toroid core	red	Toroid			Band 2: 4-8 MHz
❏	L6-core	T25-2 toroid core	red	Toroid			Band 2: 4-8 MHz
❏	wire 2	#30 enameled magnetic wire		Misc			Band 2: 4-8 MHz
❏	C10	100 pF 5%	101	Ceramic			Band 2: 4-8 MHz
❏	L5	2.1 uH 24T #30 0n T25-2 (14")	red	Coil			Band 2: 4-8 MHz
❏	C12	100 pF 5%	101	Ceramic			Band 2: 4-8 MHz
❏	L6	8 uH 49T #30 on T25-2 (22")	red	Coil			Band 2: 4-8 MHz
❏	C11	390 pF 5%	391	Ceramic			Band 2: 4-8 MHz
❏	L4	8 uH 49T #30 on T25-2 (22")	red	Coil			Band 2: 4-8 MHz

Band 2: 4-8 MHz Summary Build Notes

• Install the Capacitors
• Wind and Install the Coils
• Test the Stage

Band 2: 4-8 MHz Detailed Build Notes

Top of the Board

Band 2: 4-8 MHz Completed Stage

Top of the Board

Band 2: 4-8 MHz Testing

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