I don't think that you will have much luck with the MFJ used as a grid dip
meter. You will need a decent grid dip meter.
73
Gary K4FMX
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> Timothy Holmes
> Sent: Sunday, June 05, 2016 5:40 PM
> To: jim@audiosystemsgroup.com; towertalk@contesting.com
> Subject: Re: [TowerTalk] Modeling antenna traps
>
> Hi Jim
>
> I guess that goes to the crux of my question, how do I go about
> measuring
> those parameters, and, once I have done so, how do I then model them.
> This
> is turning into quite an interesting discussion. I should mention that
> I
> have an MFJ antenna analyzer with the grid dip coils if that will help,
> as
> well as a multimeter
>
> TIM
> W8TAH
>
> On Sun, Jun 5, 2016, 6:33 PM Jim Brown <jim@audiosystemsgroup.com>
> wrote:
>
> > On Sun,6/5/2016 1:20 PM, Timothy Holmes wrote:
> > > I would like to model them so that I can properly adjust them to see
> if
> > it
> > > is even worth my time, and what the performance will roughly look
> like
> >
> > To model the antenna, you will first need to measure the traps to find
> > their complete equivalent circuit. A trap is fundamentally an inductor
> > with series resistance in parallel with a capacitor with parallel
> > resistance. Near resonance, they simplify to parallel R, L, and C, but
> > above and below resonance, we need to know the R in series with L,
> > because these values affect performance on bands below the resonance
> of
> > the trap. And, of course, both Rs vary with frequency, thanks to skin
> > effect.
> >
> > 73, Jim K9YC
> >
> >
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