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HB9ABX > ANTENN 06.05.09 17:26l 42 Lines 1436 Bytes #999 (0) @ WW
BID : KJ8APEHB9EAS
Read: GUEST
Subj: Current Balun helps
Path: IZ3LSV<IQ3GO<SR1BSZ<OK4PEN<OK0PHL<OK0NHD<HB9EAS
Sent: 090506/1522z @:HB9EAS.CHE.EU [Basel JN37TM] DP6.00 $:KJ8APEHB9EAS
From: HB9ABX @ HB9EAS.CHE.EU (Felix)
To: ANTENN @ WW
Current Balun helps.
A good current balun can provide al lot of help in antenna problems.
Example:
At the H26 contest a week ago we used a G5RV at our local HAM group.
There we noted, that high ground current was flowing from the transceiver
to ground.
Such ground current may prooduce a lot of negative effects, as:
- increase of SWR
- high RF field in shack (RFI)
- reduction of radiated field
- RF effects in microphone etc.
Then, I inserted a current balun between the transceiver and the antenna
coax cable - and the ground current disappeard.
It is a genaral recommendation to use a current balun between coax and
TCVR, as this only may be helpful without negative effects.
The attenuation of the balun is neglegtable, as this is just adding
60 cm of additional coax.
How to build.
An efficient current balun for all HF bands is made as follows:
Stack three ferrite toroids FT-140-43 and fix them together with some
scotch or electric insulation tape. Then wind loosely RG-58 coax six times
through these toroids and separate the individual windings, and solder
a coax connector to both ends. Ready.
This baluns serves up to 500 watt RF.
This balun serves also perfectly to feed a half wave dipole at the center
with a coax cable. This way the dipole is fed correctly.
You find such toroids e.g. at http://partsandkits.com/toroids.php
Best 73s
Felix HB9ABX
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