[RFI] [Ham-Antennas] My Noise Problem Followup

Mon Dec 23 09:38:01 EST 2024

Speaking of Kitchen Aid.
I had to replace our 25 year old Whirlpool dishwasher last month (no RFI).  I chose a Kitchen Aid unit based on reviews.  Once replaced, on 80M I could hear the ocean waves breaking on the beach.  I don't live near the ocean.  The RFI added about 5dB to the noise floor.  Turning off the ckt breaker on the dishwasher would stop the noise.

I noticed the dishwasher had one small ferrite on the power wires with 2 passes through it.  I had to add two additional ferrites to the AC line cord (2-3 turns each) in order to eliminate the RFI.  The dishwasher is quiet now, both RFI and audio while running.

Jeff, W4DD (North GA)

-----Original Message-----
From: RFI <rfi-bounces+w4dd09=gmail.com at contesting.com> On Behalf Of David Eckhardt
Sent: Sunday, December 22, 2024 1:54 PM
To: main at ham-antennas.groups.io; Rfi List <rfi at contesting.com>
Cc: Kenneth Wyatt <wyattphoto at mac.com>; Ken Wyatt <ken at emc-seminars.com>; Greg Ella <gregella53 at gmail.com>; Terry Bullett <FrontRangeRadio at skybeam.com>; Bascombe J. Wilson <jay.wilson at vodec.net>
Subject: Re: [RFI] [Ham-Antennas] My Noise Problem Followup

Just another "source" to silence house-generated RFI (a bit of a long read, but you'll be surprised - I guarantee):

We have a house full of new appliances (10-years or newer).  All are filled with embedded SMPSs and all "with love from China".  Yes, multiple and every one..... and......everywhere!  If you believe the suppliers of these nasty RFI sources actually spend the extra $$ to include appropriate filters, shielding, and decoupling to tame these fire-breathing dragons, you're living in nervana land under a rock and/or have your head in the sand!  China doesn't give a rip!.  Nor does the FCC, these days of limited budgets.

OK, to my point.  With a full house of the nasty fire-breathing dragons, wherever they are located, I have "tamed" my antennas to just say no to their fiery emissions using every technique in the book and acquired knowledge to keep the dragons away from their electromagnetic exposures to free space.  But I still have RFI even without any antenna feedline connected to the input of my common mode choke (CMC) followed by my home brew L-network matching unit to keep the transmitter(s) happy.  What could it be?

Yesterday, I declared "war" on the nasty in-house fire breathing dragons (kept away from the antennas).  So, with my set of HF wires disconnected from the X ± j Y port of the matching network, but with the CMC and matching network still  connected to the Icom 7300 in AM position, I started in the ham shack as I'd already frisked the house and tamed everything I could with the traveling AM battery radio.  The RFI demodulated in AM as just a lot of noise with a bit of 60-Hz and harmonics, but mostly just BB noise.  As an aside, many of the kitchen appliances stood out with the AM battery radio frisk.  A robust CMC had to be constructed and installed on the AC power cord or the Kitchenaid frig/freezer.  The inside control panel emits absolutely nasty RFI, but fortunately, closure of the doors on the frig/freezer with the CMC pretty much tames that source.

OK, back to the task at hand.  As an EMC/RFI engineer for some 40+ years (now thankfully retired), I've found the easiest and many times the most effective method of isolating a source of RFI (or emissions) is "laying hands" on designated subjects.  Yea, I know, this sounds like my favorite phrase, "snake oil".  But talk with any old time and well seasoned  EMC/RFI engineer, and you'll soon discover there is no snake oil, witchcraft, sorcery, or anything involving the LHC (Large Hadron Collider in
Switzerland) involved with the practice.

What did I locate as* the* outstanding culprit?  Surprise!!  To me as well, but in hindsite, I well understand.  When I laid hands on each side of my Diawa CN-801 HP Power/SWR meter, the noise on the 7300 nearly ceased!
HUH.....? ... ... ? ..,. ?

That piece of gear is the last and PASSIVE piece of equipment preceding the 50-ohm port (after adjusting) of the matching network.  How could that be causing a problem?  Well think about it.  The single transmission line "opening" which exposes the center conductor of the route between the transceiver, amplifier, and input (50-ohm port) to the matching network is just the CN-801 and ONLY the CN-801!  Yes, even though it's passive it has sensors internal which are designed and implemented to sense both forward and reverse power and calibrated for forward power.  Those sensors are open to everything the house generates!  Yes, I was surprised at the discovery and wasthe last piece of equipment I suspected.  Source found, now what to do about it.

The enclosure to the CN-801 is all plastic - Plastic being the replacement of $$ (???????) expensive metallic and conducting enclosures of years gone by.  There are four METALLIC (!!!) screws on the back of the unit.  I connected a large gauge conductor to one of those screws and terminated the other end to the shield around my matching unit.  Guess what?  RFI GONE ! !
! !   The jumper was every bit as effective and a bit more than my laying
hands on the CN-801.  Glory be.......snake oil disproven!  After nearly a decade of searching for this source, problem located and solved.

LESSON for maybe EVERYONE:  Don't neglect your SWR/Power meter.  While it may not be the generating source, it could be the leak into an otherwise well defined and executed Faraday Cage, your transmission line.  It was the
leak for my house-generaged RFI.   Tuck this in your back pocket of tricks.

Dave - WØLEV

On Sun, Dec 22, 2024 at 5:48 PM Dave (NK7Z) via groups.io <dave= nk7z.net at groups.io> wrote:

> Stuart,
>
> You will find all sorts of RFI if you look via the portable SW radio 
> going to each source.  I would recommend you power your Ham rig with a
> 12 volt battery, then kill the house, and bring up each circuit one at 
> a time.  When you hear a source on the ham rig, then track that source.
> As a side note, once you silence a source on a circuit, kill that 
> circuit again, to make sure you don't have two or more sources on the 
> same circuit.  This process will save you a lot of time, in that you 
> are not tracking down and silencing sources that your ham station does 
> not hear...
>
> Once you have them all killed, run a 24 hour scan as described at:
>
> https://www.nk7z.net/sdr-rfi-survey-p1/
>
> and save it for next year.  I run one of these from 2-30 MHz. As close 
> to new year as I can each year.  Then I look at the previous year and 
> cry...
>
> 73, and thanks,
>
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist, RFI
> ARRL Asst. Director, NW Division, Technical Resources
>
>
> On 12/22/24 07:53, Stuart Bloom via groups.io wrote:
> > This is always a good topic. When I got into RTL-SDR, I too noticed 
> > all
> of the noise and the noise harmonics in the higher bands.
> >
> > I started with the breaker panel to try and narrow down which loads 
> > were
> causing the problems. I had a service change recently, and I was 
> involved (I’m an EE and did some major remodeling the last few years).
> >
> > Setup the RTL-SDR or in my case, my RSP2 with a laptop on the 
> > battery. I
> used a MLA-30 loop outside the house, and alternating with just a long 
> wire down low that picked up noise from inside.
> >
> > I shutdown all 28 breakers and brought each back on-line. With all
> breakers off, I noticed I had some external noise. A neighbor has 
> solar. He was giving me some noise. He had his provider come and fix s 
> faulty micro inverter.
> >
> > As I brought up each circuit, I went around the house with a small
> Grundig shortwave radio. It’s amazing what you can find. Appliances, 
> wallwarts, LED and fluorescent lamps, HVAC, etc.
> >
> > I had multiple problems:
> >
> > 1. My nice new Samsung Dryer (not much I can do to fix this now). 
> > This
> is a gas dryer, but the noise from the controller and motor were 
> noticeable. I don’t operate with the dryer on, unless it’s not noticeable.
> >
> > 2. My Goodman high efficiency furnace. This has two fan speeds and 
> > two
> gas burner levels. I was able to plug in a power filter. Helped quite a bit.
> >
> > 3. Various wallwarts. At least 25% of the cheap equipment wallwarts 
> > were
> noisey. These can be replaced, or sometimes the DC output can be 
> filtered with a clamp on ferrite. I bought 2 bags of various sized 
> clamp on or ring ferrites. Hit or miss, but worth the effort.
> >
> > 4. Shop equipment. Lots of items in the shop produce electrical noise.
> >
> > 5. New LG refridgerator. This has a “linear motor compressor”. Not 
> > too
> bad, but I could hear it with my portable radio.
> > 6. Mini-split heat pump / AC. My big one in the living room is 
> > noisier
> than the smaller 2-zone unit for the bedrooms, but not too bad. 
> Depends on the band I’m on. The MrCool 2 zone unit actually had 
> recommendations on what ferrites to add to the 240 VAC power input and 
> air handler output cables. They at least acknowledged that these newer 
> Inverter drives make electrical noise. Their tech support was helpful 
> with this. The units don’t come with the ferrite rings. The new 
> cooling/heating systems seem to all have inverter variable speed motor 
> drives now. Very efficient, but potentially very noisey.
> >
> > 7. LED and Fluorescent lights. Hit or miss. Some no problem, some 
> > very
> bad.
> >
> > 8. Solar panel inverters/controllers. Hit or miss.
> >
> > 9. I live in Los Alamos. We have a very large linear accelerator. 
> > I’m
> near the beam axis. I sometimes get some interference from it. Just 
> have to work around it.
> >
> > 10. As was mentioned make sure your noise spikes are real and not an
> artifact of your equipment. When I started with the RTL-SDR dongles 
> before I got the RSP, I too didn’t have the gain and filtering set 
> right. I was looking at artifacts of the cheap dongle.
> >
> > In conclusion, I did these checks over two weekends, and in some 
> > cases
> had to repeat the tests (didn’t find the furnace and heat pump noise 
> right away because it was summer time). I was able to reduce the noise 
> quite a bit.
> >
> > Good luck, and have fun looking for and improving your environment.
> >
> > Stu
> > KD5HVO
> >
> >
> >
> >
> >
>
>
> --
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist
> ARRL Asst. Director, NW Division, Technical Resources
>
>
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-- 

*Dave - WØLEV*
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