Perhaps others can confirm this, but I think the "cable loss mode"
requires that the far end be either opened or shorted (to give an
infinite SWR or Return Loss = 0 dB at the load), and NOT connected to
a dummy load or antenna.
73, Terry N6RY
At 05:21 PM 2008-12-18, Gary Smith wrote:
>I'm guessing someone here has a 259B. I bought a used one that was
>damaged in shipping. I sent it to MFJ for repair and it came back
>with continued issues, one of which was when I would have it tell me
>the coax loss of a 350' length of RG-213, the result was 12dB. I knew
>that was wrong so I tried it into a bird dummy load with a 4' length
>of coax and again the result was 12dB. When attached to an antenna,
>the farther from resonance, the lower the claimed dB.
>
>I returned it to MFJ citing this example as an obvious error. They
>repaired it and I just got it back today.
>
>I have the exact same results. If the center conductor is inserted, I
>see a small dB value but when the shield makes contact with the
>259B, it behaves as above.
>
>If there is no coax attached, it reads 0 dB.
>
>To offer exact numbers, I just attached my 350' of RG-213 connected
>to a 160M inverted L and:
>
>@ 1.825MHz SWR is 1:1, R=53 X=5
>
>Push the mode button once and it goes to Coax Loss and it shows 12dB
>
>If using the same antenna & coax, I adjust the tune control on the
>259B to evaluate 2.373MHz
>the SWR shows 7.3 R=17 X=66 and the coax loss shows 1.1dB
>
>I am at a complete loss as to what is going on, Based on 350' of RG-
>213 and using this calculator http://www.timesmicrowave.com/cgi-
>bin/calculate.pl I expected to see around .9dB loss not 12dB
>
>So either I am missing the point of how to read the loss or this unit
>is still incorrectly reading the line loss. If that's the case, I
>can't feel secure about anything it's revealing. I really want to
>know the radiation resistance at the antenna to know if I am seeing a
>significant difference with additional radials. I just don't trust
>this unit.
>
>Is there something I am doing incorrectly? Or is this still defective
>after two visits to MFJ over the last three weeks?
>
>Thanks, Gary KA1J
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