05-30-2022, 09:36 AM
Having two neighbors that worked at Cornell/Corcom and well as my work in industrial electronics I have accumulated a large box of line filters.
I have also changed over 12) 4' florescent ballasts from early magnetic to late magnetic with built in filtering, meaning, I have a dozen of "fluorescent" RF filters, left over.
I generally use smaller 3 amp filters inside the chassis of console radios to good advantage.
However, larger units are way overkill (20 amp).
Many of the filters use a dual pi-section common mode design. Most have a particular range of RF attenuation, such specifications, if they can be found, are useful to be sure that the application is successful.
A improperly designed (homemade) or poorly installed filter is practically useless as the RF noise will simply "go around" the filter. Of primary issue is the Earthing of the filter, too long a path or a noisy path is useless.
Filters have bypass caps, the AC pass of the caps can accumulate if filters are on multiple equipment on the same branch circuit, the ground fault detector can give way. The filter must use a ground path as the leakage current will be enough to be felt. Most of the caps in these filters use at least a 0.1 mf.
Filters do fail but very rarely, the caps will short from a high voltage, high current surge. I have seen a case rupture in an integral IEC (cord socketed) Corcom pi section filter. I was surprised to learn later this was a 30 amp 240 circuit that was layman installed without GFI... Yes, the device had an auto voltage selecting power supply...
Chas
I have also changed over 12) 4' florescent ballasts from early magnetic to late magnetic with built in filtering, meaning, I have a dozen of "fluorescent" RF filters, left over.
I generally use smaller 3 amp filters inside the chassis of console radios to good advantage.
However, larger units are way overkill (20 amp).
Many of the filters use a dual pi-section common mode design. Most have a particular range of RF attenuation, such specifications, if they can be found, are useful to be sure that the application is successful.
A improperly designed (homemade) or poorly installed filter is practically useless as the RF noise will simply "go around" the filter. Of primary issue is the Earthing of the filter, too long a path or a noisy path is useless.
Filters have bypass caps, the AC pass of the caps can accumulate if filters are on multiple equipment on the same branch circuit, the ground fault detector can give way. The filter must use a ground path as the leakage current will be enough to be felt. Most of the caps in these filters use at least a 0.1 mf.
Filters do fail but very rarely, the caps will short from a high voltage, high current surge. I have seen a case rupture in an integral IEC (cord socketed) Corcom pi section filter. I was surprised to learn later this was a 30 amp 240 circuit that was layman installed without GFI... Yes, the device had an auto voltage selecting power supply...
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
