Topband: MFJ259B QUERY

[Dan Zimmerman N3OX]

>
> I'm cutting a couple of 1/4 wave sections on topband and, in tuning for
> X=0,
> I notice that this value exists over about 30+ khz.  If I "fine tune" for
> R=1 and X=0 there is still a healthy bandwidth of perhaps 20 khz.


That seems about right, for example, for RG-213 terminated in an open
circuit.  You can use VK1OD's transmission line calculator to investigate
the predicted impedance of an open circuit stub.  Select "ZLoad" and use a
very large resistance, like "1e8" for an open circuit:

http://vk1od.net/calc/tl/tllc



> This
> complicates cutting the lines exactly where I want them.


Well, I don't know your needed precision (probably not more than you already
can get) but if you really wanted to you could use that calculator to plot a
bunch of  "theoretical" impedance points and figure out how your measurement
should look by comparison.

73
Dan