Locked Re: CAT control for Icom IC-756 Pro III #Cat_RigControl
Karl Beckman WA8NVW - NNV5BH
GM Michael. A few added comments for your excellent list:
1) If you use a powered USB expansion hub, add a ferrite toroid on the cable coming from the USB power supply.
2C) Some hams will interpret what you wrote as an excuse to cut off the ground pin of the computer or monitor power cord. NO, NO, NEVER! Instead run a separate RF ground from the computer chassis to your station RF ground.
For a laptop use the retaining screw of a DB9 or DB25 connector shell, if your device still has them.
2D) Ethernet patch cables up through CAT6 are UTP, which stands for UNSHIELDED Twisted Pairs, four to be specific. There is NO separate shield conductor in the jacket, nor a metallic shield around the RJ45 connector itself.
Just use a ferrite toroid at each end.
2E) 24 VAC transformers can be RF-bypassed using .005 ufd caps from each output lead to safety ground. You can often use the cover plate mounting screw as your ground connection.
2F) The same approach as 2E also works for external speaker audio leads.
2H) Home laundry and HVAC systems. In general, newer high-efficiency models have more RF problems. Ferrite toroids INSIDE the appliance housing can work wonders if the wiring harness has connectors in the AC line input, OR an external noise filter for the AC line cord of a washing machine can reduce RF spurs by 25 dB or more. HVAC systems with variable speed blower control systems both cause RF noise and react badly to RF fields, but I have no experience troubleshooting them.
Add home solar power to your list of common offenders. Again, no experience here.
SignaLink) You can ground the metal box shell by simply wrapping an 18ga wire (or use a small crimped ring or spade terminal) under the head of any of the screws holding the rear panel, then connect to your station RF ground.
The case is isolated from both USB and analog audio signal grounds, so this does not affect use of the USB shield isolators.. This one made a BIG difference in my shack!
DC power supply) This applies to both linear and switching designs. READ THE PS MANUAL FIRST! This step may void some manufacturers' warranty and UL/CSA approvals.
Remove any jumpers between the DC negative output lead and PS chassis or line cord ground Add a .005 ufd cap from each DC output lead to chassis ground if not already there.
NOTE: Samlex DC outputs are already isolated and bypassed, but many others, including Astron, may randomly have the negative side grounded and no RF bypassing.
Karl WA8NVW OH
in WSJTX@... supply units