Topband
[Top] [All Lists]

Re: Topband: MFJ259B QUERY

To: topband <topband@contesting.com>
Subject: Re: Topband: MFJ259B QUERY
From: Dan Zimmerman N3OX <n3ox@n3ox.net>
Date: Sun, 30 May 2010 11:59:31 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
>
> 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
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK

<Prev in Thread] Current Thread [Next in Thread>