Band2a 3.5-8 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
(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)
(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)
| Check | Designation | Component | Marking | Category | Orientation | Notes | Circuit |
|---|---|---|---|---|---|---|---|
| ❏ | C10 | 120 pF 5% | 121 | Ceramic | Band2a 3.5-8 MHz | ||
| ❏ | L05 | 3.5 uH 32T #30 on T25-2 (15") | red
 | Coil | Band2a 3.5-8 MHz | ||
| ❏ | C12 | 120 pF 5% | 121 | Ceramic | Band2a 3.5-8 MHz | ||
| ❏ | L04 | 8 uH 49T #30 on T25-2 (22") | red
| Coil | Band2a 3.5-8 MHz | ||
| ❏ | C11 | 270 pF 5% | 271 | Ceramic | Band2a 3.5-8 MHz | ||
| ❏ | L06 | 8 uH 49T #30 on T25-2 (22") | red
| Coil | Band2a 3.5-8 MHz |
Band2a 3.5-8 MHz Summary Build Notes
- Install the Capacitors
- Wind and install the coils
- Test the Stage
Band2a 3.5-8 MHz Detailed Build Notes
Top of the Board
Install the Capacitors
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | C10 | 120 pF 5% | 121 | Ceramic | ||
| ❏ | C12 | 120 pF 5% | 121 | Ceramic | ||
| ❏ | C11 | 270 pF 5% | 271 | Ceramic |
Wind and install the coils
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | L05 | 3.5 uH 32T #30 on T25-2 (15") | red
| Coil | ||
| ❏ | L04 | 8 uH 49T #30 on T25-2 (22") | red
| Coil | ||
| ❏ | L06 | 8 uH 49T #30 on T25-2 (22") | red
| Coil |
Band2a 3.5-8 MHz Completed Stage
Top of the Board
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.
Test Measurements
| Testpoint | Units | Nominal Value | Author's | Yours |
|---|---|---|---|---|
| Point "A" to Point "A" | ohms | 0 | TBD | _______ |
| Point "B" to Point "B" | ohms | 0 | TBD | _______ |