Powerline Noise Filters

[W1GFH]

Any opinions on the efficacy of these things? They come in all prices and sizes, and are usually placed on the AC line of devices that radiate RFI. But I wondered if they would have any effect when placed in an HF receivers power line to diminish neighborhood hash and fluorescent light noise.

Cheapo example seen on eBay:

http://cgi.ebay.com/Corinex-CXF-CXP-200-Powerline-Noise-Filter_W0QQitemZ290377179269QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item439bd42085

The typical circuit for these things use inductors and caps in parallel to ground. Any opinions, gripes, anecdotes, etc. would be appreciated.

[Bill, KD0HG]

Any opinions on the efficacy of these things? They come in all prices and sizes, and are usually placed on the AC line of devices that radiate RFI. But I wondered if they would have any effect when placed in an HF receivers power line to diminish neighborhood hash and fluorescent light noise.

Cheapo example seen on eBay:

http://cgi.ebay.com/Corinex-CXF-CXP-200-Powerline-Noise-Filter_W0QQitemZ290377179269QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item439bd42085

The typical circuit for these things use inductors and caps in parallel to ground. Any opinions, gripes, anecdotes, etc. would be appreciated.

If used on a receiver, the only benefit would be if the AC line was acting as the receiver's antenna. They need to be on the offending "transmitting'" device instead.

I have a few stuffed into electrical boxes with earlier-generation light dimmers, where they helped a lot. Standard L/C supressors is what they are.

[KB2WIG]

I, being tha picky type of person, noted that noise reduction is  up to 50 dB. Which means that 0 dB reduction is consistent with the manufacturers claims. The fact that it has the Made in China label does not enter into the discussion.


klc

[N2DTS]

They are just coils and caps, and will likely work fine, but only when they are used on the device generating the noise, they do nothing on the receive end.

Brett

[W1GFH]

Makes sense. Long ago I snipped out the "AC Line caps" that were in my recvr power supply on both sides of the line to ground. But now I am wondering if filtering the receiver line might actually help, since RFI below 30Mhz is conducted via the AC line.

[WQ9E]

If you cannot attack the noise at the source then your next best bet is to use one of the noise canceling boxes with a noise sense antenna.  You can also try building your own, some of the early designs (Frank Jones as I recall) had the phasing/attenuation  circuit built in as part of the receiver. 

Depending upon your noise and antennas, this solution might work very well.  I use a full wave horizontal loop on 75 and a couple of years ago I was intermittently plagued with a lot of line noise and I found that some of my vintage Grundig portables did better with their built in whip (vertical versus horizontal polarization).  I built one of the noise canceling circuits and just used a pickup wire near one of the line cords and it was very effective in quenching the noise from the loop.  Fortunately I haven't needed to use this device in awhile but with the lousy power line maintenance I am sure it will come in handy again.

Rodger WQ9E

[W2PHL]

I have used that style of filter with much success on Zenith Trans-Oceanic and all American 5 type radios. Those radios do not have a mains transformer and pickup everything riding on the A/C wiring. The filter I have is made by Isobar. The same filter on my R-390/A makes no difference.

[ke7trp]

Yep.. I use the ISOBAR type.   The one on my RXers is the Tripp lite  ISOTEL ultra 4.  It claims 50 DB and then two outlets at 75 DB. 

C

[KM1H]

The AC line caps were primarily to bypass HV spikes to ground and protect the rectifier tube.

I use a homebrew balanced AC line filter followed by a magnetically shielded isolation transformer followed by a SOLA CVT that powers the CW/SSB equipment bench. The TS-940's also have the power cords wrapped several times thru a FT240-77 toroid. The improvement on receive is VERY noticable. I havent gone to that extreme yet on the BA bench but Ive been collecting the parts.

Carl
KM1H