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

[Steve Hunt]

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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