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HB9ABX > TECHNIK 14.06.20 10:04l 50 Lines 1902 Bytes #999 (999) @ WW
BID : E6UDB0FHN03B
Read: GUEST
Subj: Current Balun / Current Choke
Path: IW8PGT<IZ3LSV<DB0ERF<DB0RES<DB0OVN<DB0GOS<DB0RBS<DB0FHN
Sent: 200614/0753z @:DB0FHN.#BAY.DEU.EU [JN59NK Nuernberg] obcm1.07b12 LT:999
From: HB9ABX @ DB0FHN.#BAY.DEU.EU (Felix)
To: TECHNIK @ WW
Reply-To: HB9ABX @ HB9EAS.CHE.EU
X-Info: Sent with login password
Current Balun / Current Choke
A balun is a device, which allows to feed a symmetrical antenna (e.g. dipole )
with an asymmetrical line (e.g. coax cable) and vice versa.
It is balancing an unbalanced input.
Broadband current balun 1,8-30 MHz:
1.Version: 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.
Make on the left and on the right side each 4.5 turns!
(better is teflon coax RG316)
2. Version: 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.
Static discharge
If the antenna has no connection to ground, add a small 10 K resistor between
center conductor and braid of the coax to discharge static electricity.
This prevents "tac-tac" from statics.
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.
73 de Felix, HB9ABX ( felix-abx at gmaxx.ch )
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