R:190709/0858Z 32668@N3HYM.MD.USA.NOAM BPQ6.0.18
R:190709/0903Z @:GB7CIP.#32.GBR.EURO #:11799 [Caterham Surrey GBR]

From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW

By G8MNY (New Feb 12)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

With connection to add ons to to your rig there is a hazard that can burn out or dammage ground wiring in your... PC, Noise Eliminating LS, Preamps
Powered Auto ATUs, & rotators etc.

The cause is high DC or RF currents being allowed to flow over signal leads cause by faulty earths & earth loops.


┌────────┐ + 20A
│ ├─────┬──────────────┐ In this example the
│ Power │ │ ┌─┴─┐ the rig is earthed only
│ │ ┌──┴──┐ LS lead │ │ via the LS.
│ Supply │ │Noise├─────────┤Rig│ Damage can be to..
│ │ │ LS ├─────────┤ │ Rig LS socket wiring,
│ │ └──┬──┘ └─┬─┘ Rig PCB,
│ ├─────┴─────//───────┘ LS lead,
└────────┘ - Failed/poor Noise LS PCB,
Rig Earth Noise LS Power lead.

Using no PSU earth connection & only earthing via the rig connection is a possable cure for low current accessories.

┌────────┐ + 20A
│ ├─────┬──────────────┐
│ Power │ │ ┌─┴─┐
│ │ ┌──┴──┐ LS lead │ │
│ Supply │ │Noise├─────────┤Rig│
│ │ │ LS ├─────────┤ │
│ │ └──┬──┘ └─┬─┘
│ ├────────────────────┘
└────────┘ -

In the next example there is both DC & RF problems.

┌────────┐ + 20A
│ ├───────┐ \│/
│ Power │ ┌─┴─┐ │
│ │ │ ├─┘ ┌──────┐
│ Supply │ │Rig│ AF Lead │Laptop│ VGA Lead ┌──────┐
│ │ │ ├─────────┤ ├──────────┤SCREEN│
│ │ - └─┬─┘ └───┬──┘ └──┬───┘
│ ┌------├────//─┘ ┌─┴─┐No DC │
└─┬──────┘ Failed/poor │PSU│earth MAINS
MAINS Rig Earth └─┬─┘ Earth
Earth MAINS

DC can dammage...
PSU earth wiring & Mains lead,
Rig AF socket/PCB,
AF lead, Laptop mother board,
VGA lead, Screen, & Screen power lead.

If there is no DC fault but RF voltage on the rig, RF currents can damage..
Rig AF socket/PCB,
AF lead, Laptop mother board,
Latop PSU's mains RF filter,
VGA lead, Screen.


See my Tech Buls on "BHI Noise Eliminating DSP LS", "A Simple V.O.X. Circuit", "PSK31 interface isolation".

Y Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP


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