The schematic above is a simple up converter which I used in conjunction with a short-wave receiver to quite successfully to monitor solar flare activity a few years ago. You can use a 3.5 or 4 MHz crystal for Y1 to up convert from about 10 KHz to 150 KHz to either 3.510 or 4.010 MHz respectively. A long wire antenna was used here but a VLF loop antenna would probably perform better and allow you to null down the VLF station monitored so that the sudden enhancement of signal can be better viewed in cases where the VLF station is too strong. I used the Loran C signal at 100 KHz. No experiments were done with sudden enhancement of atmospherics using this converter.
This converter appears in the Radio Astronomy Teachers
Notebook, available
from Radio-Sky Publishing.
PARTS LIST
| C1,C4 | 150 pf |
| C2,C3 | 680 pf |
| C5, C8, C10, C14, C15, C16 | .1 mf |
| C6 | 100 pf |
| C7, C11 | 35-270 pf trimmer |
| C9 | .01 mf |
| C12,C13 | 220 pf |
| D1,D2 | 1N914 |
| Y1 | 3.5 or 4.0 MHz computer crystal |
| L1, L2, L3 | 680 micro Henry choke (avail http://www.digikey.com) |
| L4, L6 | 44 turns on T-50-2 core |
| L5 | 4 turns over L4 |
| L7 | 6 turns over L6 |
| Q1 | 40673 Dual Gate MOSFET (obsolete) use NTE222, BF981, BF961, or 3SK88 |
| Q2 | 2N3904 |
| R1, R6 | 4.7 K |
| R2, R5 | 10 K |
| R3, R7 | 330 ohms |
| R4, R8 | 150 ohms |
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