Re: New file uploaded to PHSNA (Balun meaqsurement unsatisfactory)


Pravin
 

Hi Ignacio,
                  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.

73
DE AB9XC
(Pravin)
 




From: "EB4APL eb4apl@... [PHSNA]"
To: 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:
 
Hi Nivar_P. Your writeup says you are using two identical cores with identical 8 turns of bifilar windings configured to work as a 4:1 balun. Not sure how you are electrically interconnecting the bifilar windings on the two cores. Maybe you could post a schematic? Most baluns I've seen use a single core.  It is acting like you don't have good enough coupling between the windings in the bifilar pairs.  What is your physical configuration of the bifilar windings? The wires need to be closely adjacent to each other in the bifilar pairs to act as a transmission line at high frequencies.

"Digital Steve" K1RF



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