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From: Richard O'Neill
Date: 11/9/00
Time: 12:36:35 PM
Remote Name: 158.252.115.67
Mike, Rather than trust Q calculations, I measure my coils. Reviewing my data and your coil parameters, I can offer these comments and suggestions. The coil you describe should work well with expected Q's in the 300 or more range. If you increased the wire size to #16 and the diameter to 4" or more on a lower loss form, you could expect Q's in the 400+ range. This assumes the turns are properly spaced. The effect of this change on selectivity performance would be subtle but might be noticeable on weak, closely spaced stations. ABS plastics do have some loss but are better than cardboard. Polystyrene and HDPE are preferable lower loss form materials. I have used thin walled pvc drain pipe with #16 enamel and noticed selectivity improvements over #22 enamel coils of 3" diameter. Mostly, I have found that seeking higher Q through larger wire and larger lower loss forms, didn't really give me much return for the investment of time and materials. The significant increase was with litz wire. Bigger improvements came with a double tuned configuration, sound powered phones and matching transformer. Diode selection also plays a significant roll. Hope this helps.