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G8MNY  > TECHNI   17.11.21 11:00l 72 Lines 2570 Bytes #999 (0) @ WW
BID : 53279_GB7CIP
Read: GUEST
Subj: Rig DC Power & RF Hazards
Path: PI8DRE<PI8CDR<DB0RES<ON0AR<OZ5BBS<CX2SA<ED1ZAC<GB7CIP
Sent: 211117/0933Z @:GB7CIP.#32.GBR.EURO #:53279 [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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