Dugas, Jason A. (JSC-EP) wrote:
>I am constructing an amplifier and am using the Tetrode boards to run
>the power supplies. I had a question concerning the grounding scheme:
>
>The ground potential for each of the boards is tied to the chassis of
>my power supply (per your instruction) using 20AWG wire or so. Most of
>the signals that come out of the power supply (such as the high voltage
>supply (HV Enable 12V), ALC, PTT, G1, G2, etc) are all referenced to
>this ground chassis return.
>
>My question is, "What precautions, if any, should I take against ground
>loops and/or voltage drops in the return wiring between the boards and
>chassis and the power supply unit and each respective load?"
>
>For instance, depending on the current level, there will be some finite
>voltage drop in the return leg which will cause ground not to be
>exactly 0V. Obviously this is practically true in all circumstances,
>but at what level should I be concerned?
>
>The reason I ask is that I am doing pinouts for a circular military
>connector that will bring out all the various signals (referenced
>above, previously) for distribution to the HV supply, amplifier, and
>transceiver. In doing so I noticed that I will have many pins connected
>to "CHASSIS GROUND" but potentially only one wire coming from CHASSIS
>GROUND to the connector, internal to the power supply.
It helps to keep the leads between the two control boards reasonably
short. If you use rather heavier wire for the CATHODE/CHASSIS bonding,
this helps to prevent nuisance tripping of the protection circuit due to
slightly different "ground" potentials on the two boards (aka "ground
bounce").
If you can, I would recommend uprating the ground connections between
the boards to about 14AWG (stranded wire is fine, of course).
The same considerations apply to the interconnections between the RF
amplifier, the control boards and the HV supply. Ideally, the ground
buses should be significantly larger than any others, and the ground
bonding for the HV supply should also be duplicated for safety.
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek/boards
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