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HB9ABX > TECH 26.08.06 10:35l 49 Lines 1695 Bytes #999 (0) @ WW
BID : J4LJN4HB9EAS
Read: DL1LCA DJ9UI DL1RX DL8FBH GUEST OE7FMI
Subj: Current Balun Construction
Path: DB0FHN<DB0RGB<DB0SL<DB0FSG<HB9EAS
Sent: 060826/0833z @:HB9EAS.CHE.EU [Basel JN37TM] DP6.00 $:J4LJN4HB9EAS
From: HB9ABX @ HB9EAS.CHE.EU (Felix)
To: TECH @ WW
Current Balun / Current Choke / Choke Balun
---------------------------------------------
This is a 50 Ohm 1:1 balun and serves perfectly to feed
a symmetrical antenna with a coax,
or to be inserted into a coax to prevent shield current
and feedline radiation.
Insertion point is just at the antenna feed point.
Instruction to make a Broadband current balun 1,8-30 MHz:
Version 1: for 100 Watt: -
Ferrite ring FT140-43 with RG58
(or FT114-43 with coax RG174, ok for 100W)
1 ring is sufficient, by using 2, the efficiency on 1,8 MHz will increase
you will need 2 rings for 200 W and RG 316.
With 2 rings, you place one over the other and make
common windings through both.
Version 2: for 1 Kilowatt: -
Ferrite ring FT240-43 with coax RG58
(better is teflon coax RG142)
Winding technique is important!
With coax from outside to the ferrite ring. Wind 4 1/2 turns on one
half of the ring, then through the ring to the other side and wind
again 4 1/2 turns.
The end of the winding should then be on the opposite position
of the beginning of the winding.
Then, fix the winding with PVC tape.
Finally, place the balun into a weatherproof housing.
If the enclosure is metallic, make sure that the input ground
connection is not shorted to the output ground connection
by using isolated connectors.
This type of balun is more efficient than the W2DU design,
where a number of ferrite rings is pushed over the coax cable.
It is also the better choice than winding the coax cable in a loop of several turns.
More details with explaining pictures are found at:
home.tiscali.ch/hb9abx
Felix HB9ABX
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