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On Fri, 29 Dec 2006 09:04:01 -0500, chuck wrote:
The MFJ-259 has a resolution of one ohm and the uncertainty of that LSD is probably more than an ohm. You may not be able to reliably detect small improvements using the MFJ. Hi Chuck, This is rather focused at the wrong end of the scale. The antenna's radiation resistance is going to be lost at the 1 Ohm resolution of the scale. A 12 foot radiator in the 80M band presents us with about 5 Ohms (a 10:1 mismatch) resistance with so much reactance that it would wrap the needle around the peg at the wrong end of the SWR scale. However, the "lucky" ones may in fact see a SWR that is closer to 2:1, only to be satisfied that 20 of those Ohms comes from poor connections, coax, heated coils, and chassis loss. We can all agree that the MFJ is perfectly capable of measuring 20 Ohms without issues of error (yes, there will be error, but it won't be focused in the last digit). You will also be able to see that 20 Ohms diminish TOWARDS the 5 Ohm Rr when you struggle to IMPROVE the situation. Even if that is everyone's goal, it is rarely achieved; and certainly not because accuracy foiled them. 73's Richard Clark, KB7QHC |
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