Band2a 3.5-8 MHz Introduction


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

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):

See the detailed techniques for winding toroidial coils

(go directly to build notes)

Band2a 3.5-8 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)
Band2a 3.5-8 MHzschematic (go directly to build notes)

Band2a 3.5-8 MHz Bill of Materials

Stage Bill of Materials

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

C10120 pF 5%121Ceramic  Band2a 3.5-8 MHz
L053.5 uH 32T #30 on T25-2 (15")red redCoil  Band2a 3.5-8 MHz
C12120 pF 5%121Ceramic  Band2a 3.5-8 MHz
L048 uH 49T #30 on T25-2 (22")red redCoil  Band2a 3.5-8 MHz
C11270 pF 5%271Ceramic  Band2a 3.5-8 MHz
L068 uH 49T #30 on T25-2 (22")red redCoil  Band2a 3.5-8 MHz

Band2a 3.5-8 MHz Summary Build Notes

Band2a 3.5-8 MHz Detailed Build Notes

Top of the Board

Band2a 3.5-8 MHz Top View

Install the Capacitors

C10120 pF 5%121Ceramic 
C12120 pF 5%121Ceramic 
C11270 pF 5%271Ceramic 

Wind and install the coils

L053.5 uH 32T #30 on T25-2 (15")red redCoil 
L048 uH 49T #30 on T25-2 (22")red redCoil 
L068 uH 49T #30 on T25-2 (22")red redCoil 

Band2a 3.5-8 MHz Completed Stage

Top of the Board

View of Completed Top

Band2a 3.5-8 MHz Testing

Visual heck

Test Setup

Using very good lighting and magnification, carefully inspect the solder joints to identify bridges, cold joints, or poor contacts.

Pay especial attention to the joints on the inductors. If necessary, touch up the joints with your iron and/or some flux.

Continuity Tests

Test Setup

    • This tests for continuity in the "chain" of inductors for this band
    • The graphic below shows two continuity chains and their associated test points on the bottom of the board.
    • The "A and B chains"are shown using lettered dots and lines. :
    • For each of the two segments (A-A and B-B), measure the resistance between the dot pairs - you want ~0 ohms.
    Continuity Tests

    Test Measurements

    TestpointUnitsNominal ValueAuthor'sYours
    Point "A" to Point "A"ohms0TBD_______
    Point "B" to Point "B"ohms0TBD_______