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565cfadjust [2007/04/18 21:44] n5na |
565cfadjust [2013/04/06 01:03] (current) n2fq |
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| -Now check your work by first noting VFO zero beat (A=B is a simple way to keep track), and tune VFO to both sides to the same meter mark you used in 3 above, noting both frequencies. If you've done it correctly, both should be at an equal offset from the zero beat frequency. | -Now check your work by first noting VFO zero beat (A=B is a simple way to keep track), and tune VFO to both sides to the same meter mark you used in 3 above, noting both frequencies. If you've done it correctly, both should be at an equal offset from the zero beat frequency. | ||
| - | <box red left 80%>BTW, if you install the Inrad 762 in the 1000 Hz position, you don't need either 500 or 250 Hz filters since it exceeds the IMD performance of both. Details below: | + | <box red left 100%>BTW, if you install the Inrad 762 in the 1000 Hz position, you don't need either 500 or 250 Hz filters since it exceeds the IMD performance of both. Details below: |
| http://users.vnet.net/btippett/inrad_.htm </box> | http://users.vnet.net/btippett/inrad_.htm </box> | ||
| 73, Bill W4ZV | 73, Bill W4ZV | ||
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| + | **Alternate method for adjusting the 250Hz and 500Hz CF Using Spectrogram** | ||
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| + | -A PC with sound card is needed | ||
| + | -A copy of Spectrogram.exe and a cable from rig audio out to PC mic input | ||
| + | -The registration for the program is optional since the 10 minutes it runs is ample time to do the adjustment | ||
| + | -A copy of the pdf titled "Using Spectrogram To Measure Filter Response" by | ||
| + | John Grebenkemper, KI6WX that will help with the initial setting of the program. | ||
| + | -Use a noise generator at the antenna input or use an empty spot on a band and use the background noise. | ||
| + | -Connect the rig audio out to the computer's sound card. | ||
| + | -Start Spectrogram and use the above document and set the initial settings. This is trivial and will take a few minutes. | ||
| + | -Place the rig BW just a tad less than 500Hz to engage the 500 filter. | ||
| + | -Under the menu item on the rig select 500Hz CF Adj. | ||
| + | -In Spectrogram, place the cursor (usually a cross hair) in the center of the bandwidth shown. | ||
| + | -Or you can calculate it by subtracting the lower skirt edge from the upper skirt edge, dividing that result by 2, and adding this to the lower edge reading. | ||
| + | -Back on the rig, use the Multi knob to center it. | ||
| + | -Repeat for the 250Hz by setting the rig's BW to a tad less than 250Hz. | ||
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| + | Here is a short Youtube video depicting what I'm trying to describe above http://youtu.be/7Pcp4pU2VwM | ||
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| + | 73, Fernando N2FQ/6 | ||
