Intro to Elmer200 Series on Oscillators Page

schematic K7QO's schematic of a noise generator in PDF.

Here is the parts list.

3x 2N2222As

1x zener diode with 3.9V to 6.8V value

3x 22K resistors 1/4W

3x 1.2K resistors 1/4W

1x 680 ohm resistor 1/4W

4x 0.01uF mono or disc capacitors

9V battery or power source

Manhattan PC board and pads for construction or use your choice of homebrew construction.

Build the noise bridge in segments and test as you go.

Using the schematic above start construction using D1, R1, R2, R3, C1, C2, and Q1. This will give you a noise generator with output from C2 that gives S7 noise levels on 40m into a TenTec Argonaut V with calibrated S-meter. This with the values in the schematic and if you substitute with parts you have then you will get a slightly different value. Of course, depending up what receiver you are using also makes a difference. As they say, mileage may vary. Current drain on a 9V battery was 7.5mA.

Now add parts R4, R5, Q2, and C3. If found that this gave me 10dB over S9 readings on 40m. Current drain on a 9V battery was 12.3mA.

And to finish off the project add parts R6, R7, Q3, and C4. This gave me 30dB over S9 with 14.1mA drain on the battery.

With the noise generator and a calibrated signal generator like the Elecraft XG1 you can now begin to examine the sensitivity and filter response of one or more receivers. Below is some examples and I will add detailed information in the next few days as time permits. Enjoy.

The following experiments were made using a free program called baudline that runs under LINUX only. There are other free audio spectrum display programs that run under Windows XP and other operating systems. I'll try to get some demonstrated, but in the meantime use your expertise using google to find free software.

I took the output from the receiver being tested and fed it to an audio splitter so that I could use earphones and feed the audio to the sound card on my PC running baudline. I recommend you do this to have the audio set at the level you would be using in normal day to day operation. Adjust the input level to the sound card to a reasonable level and not overdrive the card when you are listening to signals. I'll show you what happens below.

Figure 1 TenTec Argonaut V listening to faint signal on 40m.

Figure 2 TenTec Argonaut V with volume at minimum to see artifacts in sound card hookup.

Figure 3 TenTec Argonaut V tuned to 7.05000MHz with BW=3.0K on dummy load.

Figure 4 TenTec Argonaut V tuned to 7.05000MHz with BW=1.9K on dummy load.

Figure 5 TenTec Argonaut V tuned to 7.05000MHz with BW=1.8K on dummy load.

Figure 6 TenTec Argonaut V tuned to 7.04000MHz with BW=3.0K with noise generator.

Figure 7 TenTec Argonaut V tuned to 7.05000MHz with BW=2.0K with noise generator.

Figure 8 TenTec Argonaut V tuned to 7.05000MHz with BW=750Hz with noise generator.

Figure 9 TenTec Argonaut V tuned to 7.05000MHz with BW=200Hz with noise generator.

Figure 10 TenTec Argonaut V tuned to 7.04000MHz BW=200Hz with Elecraft XG1 at 50uV.

Figure 11 TenTec Argonaut V tuned to 7.04000MHz BW=200Hz with Elecraft XG1 at 50uV and high volume.

Figure 12 Elecraft K1 tuned to 7.04000MHz FL1=1.5K

Figure 13 Elecraft K1 tuned to 7.04000MHz FL2=700Hz

Figure 14 Elecraft K1 tuned to 7.04000MHz FL3=400Hz

Figure 15 Elecraft K1 tuned to 7.04000MHz XG1 at 50uV

Figure 16 Elecraft K1 tuned to 7.04000MHz XG1 at 50uV and hearing lost

Figure 17 Elecraft K1 tuned to 7.04000MHz XG1 at 50uV and still visible with software

Figure 18 Elecraft K1 tuned to 7.04000MHz XG1 at 1uV

Figure 19 Elecraft K1 tuned to 7.04000MHz XG1 at 1uV for calibrate

Figure 20 Elecraft K1 tuned to 7.04000MHz XG1 at 1uV and barely readable

Figure 22 Elecraft K2 7.039MHz XG1 BW=1.5KHz FL4

Figure 23 Elecraft K2 7.039MHz XG1 BW=700Hz FL3

Figure 24 Elecraft K2 7.039MHz XG1 BW=400Hz FL2

Figure 26 Small Wonder Labs DSW-II 40m -- noise bridge

Figure 27 Small Wonder Labs DSW-II 40m -- no noise bridge

Figure 28 Small Wonder Labs DSW-II 40m -- XG1 50uV

Figure 29 Small Wonder Labs DSW-II 40m -- freq readout

Figure 30 Small Wonder Labs DSW-II 40m -- tuning around the frequency showing the steps.

Figure 31 Small Wonder Labs DSW-II 40m -- XG1 50uV

Figure 32 Small Wonder Labs DSW-II 40m -- XG1 1uV

Figure 33 TenTec 1340 40m -- XG1 50uV

Figure 34 TenTec 1340 40m -- XG1 1uV

Figure 35 TenTec 1340 40m -- noise source

Figure 36 Small Wonder Labs SW-40+ -- XG1 50uV

Figure 37 Small Wonder Labs SW-40+ -- XG1 1uV

Figure 38 Small Wonder Labs SW-40+ -- noise source

Figure 39 NorCal Sierra -- noise source

Figure 40 NorCal Sierra -- XG1 50uV

Figure 41 NorCal Sierra -- XG1 1uV