Wall_Wart RFI and Where did all those linear wall-warts go?
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| Nov 18th 2016, 21:50 | |
AC0XUTotal Topics: 0 Total Posts: 0 |
In my perpetual battle to combat RFI, I have replaced nearly all of my household copper gigabit ethernet with fiber. However, I now find that the wall-warts that power the fiber switches and media converters generate RFI by conduction through the DC and AC lines and by radiation through the plastic cases. The Ethernet-related RFI is more localized but not much better! I have been completely unable to find LINEAR, REGULATED wall-warts to replace the switched ones that are SO noisy. There are still some linear (transformer) wall-warts on the market, but they are not regulated, consisting of just a transformer, bridge rectifier, and capacitor. For example, a nominal 9 volt linear wall-wart may put out 12 or 13V at no load, which is too much for some electronic devices, They overheat. While I am willing to pay more for an old-fashioned, linear regulated power supply, what is available is large in capacity, size and price (e.g., 20A+, 20Lbs, $150). There are also audiophile power supplies which are overkill and expensive. I know that some hams try to run everything off a main 12V power supply (with some other solution obtained for 9V devices), but running DC power lines all over the house is a lot of trouble and they would pick up noise that would have to be filtered out to boot. I believe that part of the drive to switching power supplies has been to increase efficiency. Some websites praise these monsters as great innovations (obviously, not hams)! Also, it seems that the Chinese can manufacture a 60KHz tesla coil aka wall-wart much more cheaply than make 60Hz transformers. However, surely there are ways that a non-RFI-emitting power supply can handle varying loads while still providing high efficiency.... Before I break down and start building compact linear regulated supplies from scratch, does anyone know of a source for reasonably priced 9 and 12 V linear, regulated power supplies in the 0.5 to 5 amp range? Thanks! James AC0XU |
| Nov 19th 2016, 21:21 | |
aa6eTotal Topics: 0 Total Posts: 0 |
They seem to exist. Try Jameco. E.g. This page 73 Martin AA6E |
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