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VK4ZR > POWER 06.07.03 03:02l 63 Lines 2466 Bytes #999 (0) @ WW
BID : A40601VK4ZR
Read: DB0FHN GUEST OE7FMI
Subj: Re: that negative fuse..
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<ON0AR<VK3TE<VK4TRS
Sent: 030706/1936Z @:VK4TRS.#BNE.QLD.AUS.OC #:42765 [Calamvale] FBB7.00i
From: VK4ZR@VK4TRS.#BNE.QLD.AUS.OC
To : POWER@WW
If you wish to protect your transceiver from an internal failure then it
may be worth while fusing the negative lead of the transceiver unless you
ensure your transceiver is solidly earthed to the car's metal body.
Explanation.
If the main earth strap (to the metal body of the vehicle) from the
negative terminal of the battery becomes loose then all components within
the car that are connected to the metal chassis which is used as the
negative return of the battery will be affected.
If the Radio Transceiver is mounted in the vehicle but not actually
connected to the metal body of the vehicle then the antenna coax may
provide a circuit to the metal body of the vehicle.
If another wire is run from the negative terminal of the battery to the
Radio Transceiver, this wire will provide a return path for any component
which uses the car body for the negative battery return.
The complete path for any current will be from the negative terminal of
the battery, through the Transceiver's negative lead, through the negative
PCB etc and finally through the receiver aerial coil to the transceiver's
antenna which is usually connected via a loading coil back to the car's
metal body. This assumes that the antenna coax shield is not connected to
the main negative lead of the Transceiver.
The transceiver's receiver aerial input coil is usually made of very fine
wire and therefore any excessive current will cause this wire to fuse and
cause the transceiver to fail.
This will only happen if the main earth strap from the negative terminal
of the battery becomes loose and goes high resistance.
It is only a vague possibility that the above will happen but have you
ever heard of Murphy's Law!.
If you value your transceiver it may be worth while fitting this negative
fuse just in case Murphy is around!!
73 - Kevin, VK4ZR @ VK4TRS-1
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Message timed: 23:32 on 2003-Jul-05
Message sent using WinPack V6.80
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Radio:- ICOM IC-3200A 25 watts
Antenna:- Homebrew 2 Metre Ground plane 4.5 metres above ground
Computer:- Compaq 5166 deskpro - 128 MBytes RAM
TNC:- PK-88
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Brisbane Amateur Radio Club Member
Radio Amateurs Old Timers Club of Australia Member
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