Hi Brian,
Thanks for your reply!
The 6 or 7 ohms is only the *reactance* reading, not the
resistance reading and at this point I am only recording
reactance which as you said, should be zero at resonance.
There must be some reactance in there somewhere since
the reading is zero with a 50 ohm load on the 259-B.
73 es DX!
Charlie, N0TT
On Sat, 04 Aug 2001 17:00:20 +0000 alsopb <alsopb@gloryroad.net> writes:
> Hi Charlie,
>
> You are quite correct. The resonant point is that of minimum Z. In
> theory the cap and induct components exactly cancel. One is left
> with
> pure resistance.
>
> Your approach is the right one. Tune ant to resonance, then match
> it.
>
> I was wondering what kind of vertical you are using which is 6 or 7
> ohms?
> Normal quarter wave verticals are about 34 ohms. As the ant grows
> shorter and is loaded, the z drops.
>
> I think you meant to say that x will read 50 ohms when the 259 is
> terminated in 50 ohms.
>
> Trying to do the above with balanced antennas (e.g. quad loops) is a
> problem. The 259 is an unbalanced signal generator. One has to
> first
> run it into a 1:1 balun. That does sometimes cause problems by
> itself!
>
> 73 de Brian/K3KO
>
> 73 de Brian/K3KO
>
> n0tt1@juno.com wrote:
> >
> > Hi Gentlemen,
> >
> > This isn't exactly tower talk...maybe close enough...
> >
> > I have tried several methods to measure *resonance* of a
> > vertical 20m antenna (which will become a multiband
> > trap vertical).
> >
> > In tuning a antenna, I consider resonance and impedance
> > two separate subjects. Lowest SWR to me doesn't mean
> > "resonance". At this point in testing I don't really care
> > about the "input" impedance at the coax connector...the
> > antenna will be matched to the line later.
> >
> > I have made many measurements using a GDO and a
> > MFJ 259-B analyzer and I get different readings of
> > resonance depending on what method I use to couple
> > RF to the antenna. When I used the GDO, the frequency
> > was monitored with a frequency counter of known accuracy.
> >
> > I'm thinking that the lowest "X" (reactance) indication
> > on the 259-B would be THE resonant frequency, and
> > that I should connect the instrument with the shortest
> > possible leads (like a double-male coax connector)
> > to the "input" of the antenna. Is this correct? Or what
> > IS the best way?
> >
> > BTW, the "X" reading has been 6 to 7 ohms with the
> > 259-B and "X" will read zero when the 259-B is
> > terminated with a 50 ohm load.
> >
> > 73,
> > Charlie, N0TT
> >
> > ________________________________________________________________
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