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| Type-5 Preselector FINISHED | |||||||||||
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| This is it - several months of part-time contemplation, a full day designing the graphics, another two days machining the sheet metal and wiring the circuit, and a final afternoon tweeking the values for proper band coverage. It is about as tight as a passive device is going to get. I've tested several MFJ preselectors, the Palstar, and Gilfer, but none are as tight (high-Q) as this configuration (see test data here and here). "Tight" to me is at least 18-24dB at 10 kHz off center frequency. Be sure to view the progress of this unit on these 3 pages. You may also be interested in reading about the model-4 and model-3, which are also documented here. Feel free to contact me if you have any questions. |
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| This is the finished unit. The circuit worked out pretty good as designed, however it needed some tweeking to get the bands to track better with a bit of overlap on the high and low ends. | |||||||||||
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| The "Selectivity" circuitry works as desired. The "Width" and "Depth" controls work fine, but now I question how much use they'll get! | |||||||||||
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| Here's the inside of the prototype. I wanted a big chassis since I'm going to be experimenting with other modules. One is a crystal calibrator. All modern radios have digital readouts, but I have a bunch that are analog. It will have a switch to mark at 10 kHz, 100 kHz, and 1 MHz. |
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| Aug 26, 2006 | |||||||||||