Re: [TowerTalk] Beta match adds capacitive reactance on 2 el Hy-gain 40m ?

[Steve Hunt <steve@karinya.net>]

I forgot to say that the HyGain Beta match works out at about +j131 on 
40m - that's much too high a reactance to be effective. It would 
transform the 22-j25 load to 32-j24.
If I were you I'd wind an inductor.

73,
Steve G3TXQ



On 24/10/2012 14:47, Steve Hunt wrote:
> To transform 22-j25 close to 50 Ohms you need a shunt reactance of +j44
> To transform 17-j24 close to 50 Ohms you need a shunt reactance of +j36
>
> Hope that helps
>
> 73,
> Steve G3TXQ
>
>
> On 24/10/2012 10:21, DX Supply AB wrote:
> > Hello!!
> >
> > Has anyone an answer to this Beta Match behavior on a 2 el linear loaded
> > Hy-gain DIS 7-2?
> >
> > I have assembled the antenna again after some years in the garage. I
> > designed it for SWR min at 7040 kHz and measured up the
> >
> > Feed point impedance at 30 feet to Z=17 --j24 after having shortened the
> > driver a little more ( about 1 ½ ") than what is said in the manual. 
> > In line
> > with theory for a linear loaded design. Increasing height to 60 feet I
> > assume change (according to Cebik) the Z to about 22 --j25 or so. Not 
> > much
> > change.
> >
> > According to theory (and W4RNL Cebiks excellent paper on web) the 
> > only thing
> > now needed to tune out the capacitive reactance of --j24 is to add an
> > inductance of about 33 ohms. This can be done with a Beta match and I
> > started using the Hy.gain Beta match supplied with the antenna (1/4" 
> > x 72 "
> > rods spaced 2,4 " from the boom). This way final impedance ens up 
> > close to
> > 50 ohms which is good. However, inserting the Beta match worsened the 
> > Z to
> > 32,5-42 that is adding both resistance and capacitive reactance to 
> > the feed
> > point impedance. How an earth can the reactance be more capacitive 
> > with an
> > inductive Beta match over the feed point?
> >
> > Is the best thing to throw the beta match over board an build a small
> > inductor coil of 33 ohms?
> >
> > Thanking in advance,
> >
> > Kari SM0HRP
> >
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> >
> >
> >
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