[MFJ-Ameritron] MFJ-259B impedance reading

[Gene Mason]

On the MFJ 259B WHat does the Z read?  also, what does the reactance read?  also You might check the capacitance and inductance readings, they are all there for free and for a good reason. This may answer some of the good questions put forth by the viewers here.
KZ5V


> From: kf4nsradio at verizon.net
> To: mfj-ameritron at mailman.qth.net
> Date: Fri, 24 Jun 2011 16:38:09 -0400
> Subject: Re: [MFJ-Ameritron] MFJ-259B impedance reading
> 
> Ok guys, you got me. I should have been more detailed in my post.
> 
> It is an RF test termination made my TEK and is enclosed in a BNC 
> male/female adapter. There are no leads. I tested it on my bench top 
> HP digital meter, reading 51.8 ohms, and on my Fluke DMM, reading 51.7 
> ohms. Not exactly 50 ohms but pretty darn close.
> 
> Sorry for the lack of detail.
> 
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
> 
> > -----Original Message-----
> > From: mfj-ameritron-bounces at mailman.qth.net [mailto:mfj-ameritron-
> > bounces at mailman.qth.net] On Behalf Of Dick KF4NS
> > Sent: Thursday, June 23, 2011 3:04 PM
> > To: mfj-ameritron at mailman.qth.net
> > Subject: [MFJ-Ameritron] MFJ-259B impedance reading
> >
> > This group seems to have been dead for some time but will give it a
> > try anyway.
> >
> > I never tried this before but was messing with my antenna tuner and
> > decided to compare my antenna impedance reading with a precision 
> > 50ohm
> > resistor. I noticed that the resistor reads 58 ohms (much to my
> > surprise) when connected directly to the antenna jack on the  259B.
> >
> > Is my instrument in need of calibration or is this typical? I would
> > think pure resistance should read right on.
> >
> > 73, Dick KF4NS
> > St Petersburg, FL 33714 USA
> > Keep The Glow!
> 
> 
> 
> ------------------------------
> ------------------------------
> 
> Message: 4
> Date: Fri, 24 Jun 2011 00:26:07 -0400
> From: Andy <ingraham.ma.ultranet at rcn.com>
> Subject: Re: [MFJ-Ameritron] MFJ-259B impedance reading
> To: mfj-ameritron at mailman.qth.net
> Message-ID: <BANLkTi=UN=nu7fJaw8tZ4zYviS_UX==VGA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> > I never tried this before but was messing with my antenna tuner and
> > decided to compare my antenna impedance reading with a precision 
> > 50ohm
> > resistor.
> 
> What exactly does "precision resistor" mean?
> 
> Can you measure its resistance with an accurate DVM?
> 
> Is it supposed to be a good RF resistor too?
> 
> At what frequency did you measure it on the '259B?
> 
> Using what leads, or connectors?  How is it constructed?
> 
> > I noticed that the resistor reads 58 ohms (much to my
> > surprise) when connected directly to the antenna jack on the ?259B.
> >
> > Is my instrument in need of calibration or is this typical?
> 
> That depends.  See previous questions.
> 
> > I would
> > think pure resistance should read right on.
> 
> Well, "pure resistance" that is known to be exactly 50 ohms, should
> measure 50 ohms.  Why do you say it is a pure resistance, and do you
> know that it really is 50 ohms?
> 
> For example, it might be a good 50.0 ohm resistor, but inductance of
> the leads could make the Z measure higher.
> 
> Even dummy loads, which are supposed to be good over a wide range of
> frequencies, can measure off from what you'd think they ought to be.
> I've got a good dummy load that measures quite nicely; and some others
> that surprisingly do not.
> 
> Andy
> 
> 
> ------------------------------
> 
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