Re: New file uploaded to PHSNA (Balun meaqsurement unsatisfactory)
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Yes you are correct .It is a 4:1 Gunella balun. Still I propose to use ferrite beads on the cable near the feed end to reduce any residual common mode currents possible on the cable braid as the OCF dipole is not a symmetrical antenna.
From: "EB4APL eb4apl@... [PHSNA]"
Sent: Monday, January 23, 2017 5:48 PM
Subject: Re: [PHSNA] Re: New file uploaded to PHSNA (Balun meaqsurement unsatisfactory)
Probably he is using a 4:1 current type "Guanella " balun. These do several functions:1- Transform the 200 Ohm line (or antenna) impedance to 50 Ohm.
2- Transform the balanced line to unbalanced one (coax) . This where the name BALUN comes from.
3- Insure that the currents in the balanced line are symmetrical and avoids common mode currents. So it is also a common mode choke.
Functions 1 and 2 can be done with a voltage balun, the type commonly found in antenna tuners with symmetrical output. These uses a single core.
The Guanella balun needs two identical cores and windings. There is a lot info about them on internet.
73 de Ignacio, EB4APL
El 24/01/2017 a las 0:35, sbdick@... [PHSNA] escribió: