[R-390] Power Line Filter

[Tisha Hayes]

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."