[R-390] Power Line Filter

[Les Locklear]

I have a Corcom line filter in my John R. Leary modified SP-600. I can say that out of all the receivers in the shack, it is the quietest. My noise level in very low where I live even though I live in the central part of town. Power line noise in non-existent. But, when listening to real tough dx, the Leary SP-600 hears it before the others and the audio is much clearer than others. So much for bells, whistles and modern engineering marvels. All other things being equal, it has to be the Corcom line filter. Oh, it has a marvelous product detector too, so listening on ecss isn't even an issue either. It certainly drifts much less than a Drake R7A I owned a few years back and is on par with a good R-390A as far as drift goes, + or - 200 hz from turn on to half hour. I regularly listen to ssb nets and enjoy the audio much better than the other lsited receivers. One item, I do use a Timewave DSP-599zx when the standard LC filters don't cut the mustard.

YMMV
Les Locklear
Gulfport, Ms.
Dx'ing since '57
Drake R8B
Hammarlund HQ-150
Hammarlund HQ-180A
Icom IC-746 Modified
Hammarlund SP-600 Re-Engineered by John R. Leary



  ----- Original Message ----- 
  From: Tisha Hayes 
  To: r-390 at mailman.qth.net 
  Sent: Friday, October 22, 2010 12:03 PM
  Subject: [R-390] Power Line Filter


  A hospital grade Corcom line filter has better specs than what was in there.
  They are rated at either 3 or 6 amps. Add a few 130 Volt MOV's
  (line-neutral) (line-ground) (neutral-ground) and a CL-80 or CL-90 to limit
  inrush current. All of this will fit easily into the space where the old
  filter was.

  I use the hospital grade filters as they have a much greater attenuation
  factor for HF noise and very low leakage current. I picked up a dozen 6EHQ3
  filters a few years ago and install them in everything.

  http://www.cor.com/Series/Medical/HQ/

  If you look at the chart that filter attenuates common mode noise
  (line/ground) by 28-15 dB and differential mode noise (line-line) by 75-40
  dB between 500 KHz and 30 MHz. The leakage current is less than 2 uA so you
  will not be tripping out a GFCI.

  The original line filter in the R-390A was to eliminate generator noise and
  power line coupled interference from other RF gear. This was well before the
  days of computers, plasma screen televisions and CFL's. Our electrical noise
  levels are significantly higher today than they were in 1955. It only makes
  sense to put a better filter in there than what was designed 55 years ago.

  I like MOV's to catch the little transients that come in on the AC power. My
  receivers all run off of a 3 KVA UPS and sometimes the switching noise can
  be heard as well.

  If you get into the chase to eliminate all EMI/RFI then you find yourself
  purchasing RFI gasketing materials, beryllium contact stock, copper tape and
  lots of grounding materials. Thank God my nearest neighbors are a quarter
  mile away so I do not need to listen to their CFL's. Long live incandescent
  lights!

  It got so bad...<sob>, <sniff, sniff>.. I am now attending RFI anonymous
  meetings to quit from buying copper mesh for all of the air vents on the
  radio.

  My upcoming book "Confessions of a Compliance Engineer" will be hitting the
  bookshelves in 2018.
  -- 
  Ms. Tisha Hayes/ AA4HA
  ----------------
  Factory certified interoceter repair center.
  "Remember, use only genuine interoceter parts."
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