An RF-Quiet Light Dimmer

This blog first appeared in February 2016 but is just as relevant today as it was then!


 I admit it. I have an extraordinarily kind next door neighbour!

Ever since erecting a new, much bigger LF antenna several years ago, she has allowed me to run its large, three-wire 100' tophat, directly over the top of her house to a tree on the far edge of her property. As well, she removed her only light dimmer, knowing that it was creating a LOT of nasty RF 'hash' throughout the LF / MF spectrum, seriously degrading my LF reception. To hear the RF noise-signature of a typical light dimmer, listen here, on the ARRL's helpful page of 'household' RFI recordings ... that's just how it sounded here as well!

She recently did a major renovation, which included a new multi-light dining-room fixture and expressed to me a desire to be able to dim it ... oh-oh, I was definitely not looking forward to this.

I did a little web-research and soon learned that some of the most RF-quiet dimmers were being produced by Lutron. One model in particular, claimed to pay special attention to RF noise-filtering and that was the "Centurion", whose smallest model is a 600 watt-capable unit, with a large finned heatsink front plate ... model #C-600P-WH.

I decided to order one from the only dealer I could find in Vancouver that seemed to carry this line of dimmers. The cost was just a little over $40 Canadian (sells for about $25 in the U.S.A.) ... cheap enough if it would do the job!

When the unit came in, I picked it up on my next ferry trip to the city and upon my return, installed it the following afternoon. Before doing the installation, I fired-up the receiving system, tuned to 300kHz, and with the baby monitor set up beside the speaker, took the portable monitor with me.

After installing the new dimmer, I turned on the baby monitor, held my breath ... and turned on the light fixture. Wow ... not a trace of hash could be heard! Adjusting the dimmer from high to low produced no difference in the noise level. I later did a more thorough bandscan and could find no evidence of RFI, on any frequency. The only RFI that I could detect was when placing my Sony ICF-2010 close to the actual dimmer. I was unable to detect any noise further than 6" away from the lights or the dimmer!

So it seems that this model can be highly recommended, for your own home or if you have a next door neighbour 'light-dimmer problem'.

Recent Noise Mystery Solved

 

You may recall a recent blog regarding my installation of a new pair of inverted-V dipoles, fed from a common coaxial feedline at around 85'. Both antennas 'hear' very well and everything was peachy until I recently put the inverted-V's on my Perseus SDR.

I had been particularly interested in using the new high antennas for my general shortwave listening on 40m and below but what I observed was immediately troubling when listening on the 5 - 6MHz, 49m band. After much head-scratching about what I had noticed, I posted the following 'help' message to the Perseus reflector as well as to the Perseus SDR Facebook site:

Perhaps others can help explain something odd that I have just noticed with my Perseus while comparing antennas.

I was comparing signal levels and noise between a 40m half sloper and a very high dual 40/80m pair of inverted-V dipoles fed from a common feedline. Both the sloper and the dipoles are fed with 50 ohm cable and all three antennas are well matched at the low end of the band(s).

Listening to a 6 MHz signal from China National Radio around 10 am today, the signal was around S7-8 on the Perseus, using the 40m sloper. Listening to the same signal, at the same time, on the Yaesu FT-1000mp, with the high inverted-V, it was slightly better, maybe by 5-6 db and overall lower noise. I then put the inverted-V onto the Perseus and there was not even a trace of the signal! I made this check with several signals and always with the same result.

Now I suspect that the SWR of the 7MHz inverted-V when used at 6MHz, is very high and the load presented to the Perseus antenna input is likely highly reactive and far from 50 ohms but that doesn't seem to bother the FT-1000.

I then ran the inverted-V through my antenna tuner so that it effectively produced a 50 ohm non-reactive input load for the Perseus and did the tests again...with the same results. Swapping antennas for the 40m sloper once again produced the same signal levels in both the Perseus and the FT-1000.

So what is going on here and why does the Perseus balk at the 7 MHz inverted-V while listening on 6 MHz? Is there something in the Perseus front-end analog filtering system that is overly sensitive even though the reactance was tuned out via the tuner? Is it the 80m V on the same feedline as the 40m V that is causing some still unwanted reactance that is not tuned out with the tuner?

Any ideas what is happening here as it looks like I will not be able to use the inverted-V antennas on the Perseus for general SWL out-of-band listening for some, as yet unknown, reason.

As you can see, I was completely mystified by what I was hearing, or rather not hearing, and as it turned out, completely off the mark.

I received a few replies offering some possible reasons for what I was seeing but none of them proved helpful in solving my dilemma ... until Roelof Bakker (PAØRDT) weighed-in! Roelof suggested that I look at the antenna's performance while running Perseus's built-in 'HFSpan' function.

HFSpan is a stand-alone 0-40MHz spectrum analyzer, that comes with the Perseus software. Although I was aware of it, I have only used it sparingly. I next did some screen captures with all three antennas, one at a time, and sent them to Roelof.

His analysis did not take long as he immediately identified my problem ... a very high noise floor when using the mysteriously-performing inverted-V. Roelof suggested some common mode choking to eliminate the problem.

Already having an isolating transformer in hand from a previous experiment, I inserted it directly at the Perseus antenna input and looked at the noise floor again, around 40m. The transformer was wound on a small FT87-J core with a 3 turn primary directly opposite a 3 turn secondary. I was astounded to see the background noise floor drop from -85dbm to a very quiet -110dbm!

Evidently there was a lot of noise being picked-up on the inverted-V's feedline shield. Not hearing any of this noise on the FT-1000 indicated that the noise was probably associated with the Perseus power supply, the laptop or the laptop's power supply. This immediately explained why I wasn't hearing anything with this antenna when used with the Perseus.

Roelof then suggested that a 2 turn / 2 turn transformer, offering less inter-winding capacitive coupling, might provide even more isolation ... and he was right again. A further ~4dbm lowering of the ambient noise was measured.

It may not be pretty but it produced an astounding improvement!

Further comparisons between the FT-1000 and the Perseus revealed that the FT-1000 was still producing a slightly better SNR than the Perseus, when using the inverted-V so evidently there was still some noise affecting the signal. I had a few very large #43 ferrite toroids and decided to wrap a few turns (5) of the RG8-X feedline around the toroid to see if there would be any improvement.

Once again, using HFSpan, I compared the noise floor both with and without the #43 choke and saw a further 6-7 dbm improvement! Going back to comparing SNRs between the FT-1000 and the Perseus, I now saw no difference between how I was hearing on both receivers, when using the troublesome inverted-V ... eureka!

Here are the 'before' and 'after' screen shots using HFSpan, the Perseus built-in spectrum analyzer. Both screen shots were taken at the same time (mid-afternoon) and show the results of the noise mitigation work.

0-10MHz sweep - with noise problems

Same sweep, noise eliminated, signals now unmasked

As of yet, I have not determined the actual noise source. I suspected it may have been coming from the Perseus power supply or from the laptop supply but that was not the case. Perhaps it is coming from the laptop's processor via the USB cable which I will also choke and see if HFSpan reveals anything further

This problem was a great learning experience for me, in more ways than one and I am most grateful to Roelof for his detective work and experience with noise issues and for taking the time to respond to my initial inquiry. Hopefully you may find something here that can help you as well.

Trouble Free HF Antenna For The Apartment Dwelling Ham

Unfortunately we all know of or hear about hams that have given up all hope of getting on the air, once moving into an apartment or condo, where antennas are normally prohibited. One enterprising local amateur has combined early established antenna fundamentals along with sound engineering, to arrive at an elegant and highly successful solution. If you are also a 'location challenged' amateur, it may just be the thing that will help you, and others, take back your hobby and get on the air!

John, VE7AOV, has been operating from his apartment, in the heart of the very large and noisy greater Vancouver, for several years now ... not simply 'operating', but thriving, from his cozy fourth-floor apartment radio station. The wallpaper shown below would not usually be expected to grace the shack walls where antennas are not permitted!

It's soon apparent that John has also overcome the usual problem of noise ingression, from every appliance and random RFI generator in the complex. This is no lucky fluke but all by design, and delivered via an all but invisible classic antenna system made of #26 wire and a few Starbuck's stir-sticks!

600 ohm #26 balanced line

I'll let John tell you a bit more before sending you to his fascinating website, Intuitive Electronics, where you can learn more about his system and the engineering behind his successful, low-noise installation.

When it comes to a high frequency ham station, the antenna alternative chosen by most apartment dwellers is no antenna at all. The design here is a wisp of an antenna that bothers no one and which can work Japan, Australia, France, European and Asian Russia, the Caribbean, Central America, Polynesia and South America from the Pacific coast of Canada. It is a simple solution for apartment dwellers, it is a cheap solution and it causes no t.v.i. or other r.f. problems. It is far preferable to the alternative selected by so many fellow apartment dwellers: no antenna at all.

An implication that it seems to be impossible to rid from the minds of fellows using a Marconi antenna is that they are not just pumping 100 watts of r.f. into their antenna but that they are also pumping that same 100 watts of r.f. into their ground, that is to say the building’s wiring, the safety ground wiring. R.f. in the safety ground is well coupled into the power and neutral conductors of a residence and, in North American code, is even hard connected to the neutral line at the service entrance. The house wiring becomes part of the antenna system.

The ground wiring and everything connected to it is every bit as much a part of the antenna as is the live element. Both radiate just the same amount of r.f. power, fellows. The ground wiring along with every electrical power consumer in the building is worked against the live element. Thinking of what is connected to ground in your house is thinking about one side of your antenna. It’s not just appliances that get the “benefit” of r.f. The land line telephone system, the cable television system, the garage door opener, the security lights and…you name it. They are all “feeling” that 100W of r.f. With regard to r.f., there is no distinction whatsoever to be made between “hot” and “ground”.

You know the reason why vertical antennas have gained a reputation for being noisy on receive now, too. Most verticals are Marconi antennas. Both the safety ground and the neutral serve all the houses in the neighbourhood. The receiver is wired into the electrical appliances of the entire neighbourhood.

This radio station, located four stories above grade and in a wooden building full of apartments would be a worst case for r.f. in “ground”. This station has no r.f. in the station. It has no r.f. in “ground”.

The station has no interference issues. The Building Manager, the Building Superintendent and the administrator for this building’s cablevision have been aware of the station from the beginning. There has not been a single complaint of t.v.i. or any other complaint about the station. That’s a clean record extending back to 2006. There are no red faced, spluttering tenants hammering on the door of this station! At this station, all the r.f. produced by the transmitter makes its appearance out on the an­tenna. The radio station’s r.f. is not referenced to station ground. Station ground “knows nothing” about the r.f. being generated.

In the present case, that is to say a station to be operated in an apartment building, it is required to have an antenna that is “invisible”. Now it’s not possible to achieve that literally but at least the antenna should be so inconsiderable that there will be no complaints from neighbours about having to look at it. The antenna here is made of #26 A.W.G. wire. That’s wire that is 0.40mm, 0.016 of an inch, in diameter. Four stories up, it’s difficult to see the antenna and that’s even when knowing where to look for it. Part of the antenna’s run is through trees and in among the tree branches it pretty much is invisible. It does not annoy neighbours by casting a shadow; there is no shadow.

In spite if the naysayers, John's small gauge antenna has survived years of winter storms, regular occurrences here on Canada's western edge ... simply because it presents such a low cross-section compared to most conventional antenna wires.

To read more about enjoying your hobby again from your new 'restricted' location and more than likely, learn something new about old fundamentals, give John's website a very close inspection ... there is much wisdom and many gems to be found, even if you don't live in an apartment!

RFI ... Radio Spectrum's Global Warming?

courtesy: http://www.arrl.org/utilities

The FCC's recent publication of an Order and Consent Decree (DA-17-471) has me wondering if this action signals new interest in cracking-down on those who manufacture and distribute unapproved spectrum polluting noise-generating devices or is it just a once-in-awhile muscle flex with little change in overall policy ... hopefully it's the former!

Highlights of the agreed upon notice:

Section 302 of the Act authorizes the Commission to promulgate reasonable regulations to minimize harmful interference by equipment that emits radio frequency energy....Specifically....that “[n]o person shall manufacture, import, sell, offer for sale, or ship devices or home electronic equipment and systems, or use devices, which fail to comply with regulations....

.... the Commission establishes technical requirements for transmitters and other equipment to minimize their potential for causing interference to authorized radio services ... the Commission administers an equipment authorization program to ensure that equipment reaching the market in the
United States complies with the technical and administrative requirements set forth in the Commission’s rules. The equipment authorization program requires, among other things, that radio frequency devices must be tested for compliance with the applicable technical requirements in accordance with one of three authorization procedures—i.e., certification, Declaration of Conformity, or verification—prior to marketing.

... the Rules prohibits the marketing of radio frequency devices unless the device has first been properly authorized, identified, and labeled in accordance with the Rules ...


... a privately-held company that manufactures and distributes lighting fixtures that are used in residential and commercial properties ... under-cabinet LED light fixtures were reportedly causing interference to AM/FM radio transmissions. 

During the course of the investigation, the evidence revealed that ... the LED light fixtures were not tested and authorized under the Commission’s equipment authorization rules prior to marketing.

... the Bureau’s Spectrum Enforcement Division issued a Letter of Inquiry (LOI) ... directing to submit a sworn written response to a series of questions relating to ... the marketing of its LED lighting fixtures in the United States.

... continued to market the light fixtures at issue for certain times during an approximately five-month period after receipt of the LOI.

Other highlights indicate that the company in question acknowledged their violation and agreed to appoint a Compliance Officer in charge of implementing new company protocols, including the retraining and education of employees dealing with compliance issues. As well, a $90,000 civil penalty was imposed on the company for the violation.

As a point of interest, I can't ever recall seeing similar notifications being released or reported here in Canada by our FCC equivalent, the ISEDC. Hopefully they also take similar actions, but if so, they don't seem to be reporting it ... perhaps I'm just not looking in the proper places.

As I've mentioned here previously, for too many radio amateurs, the growing noise floor throughout the radio spectrum has become a global threat for the healthy pursuit of our hobby. Even if we saw the immediate  implementation of rigorous new tight standards, crackdowns and prosecutions of offenders, it may already be too late to reverse the damage we are now seeing ... in many respects, it's the 'global warming' of the RF spectrum and there may be no turning back without immediate action.

Got Noise?

courtesy: ARRL's Utility Noise (RFI) Signatures

It seems that the FCC has suddenly become interested in the radio spectrum noise floor and have struck an inquiry ... now hold on to your hats, "... to determine if there is an increasing noise problem ...". They also seek input on "... the scope and quantitative evidence of such problem(s) ..." and if further "study" is necessary.

Excuse me if I seem somewhat cynical, but where have they been for the past twenty years as RF pollution, of now unbelievable proportions, has become the norm for most amateurs living in populated regions? In view of the present ubiquitous level of noise pollution, asking this question now is really akin to closing the barn door long after the horses have escaped ... and sadly, they are going to be very difficult, if not impossible, to round-up.

As radio amateurs, we are probably high on the list of those most negatively impacted by unwanted RF crud and were probably the first to bring this issue to the forefront. Many amateurs have watched, and continue to watch helplessly, as their noise floors climb higher and higher.  For some, it happened overnight. In major cities and suburbs, it has become increasingly difficult to listen to normal AM radio because of RF noise pollution, so it's not just hams who are affected.

In many cases, the noise is powerline related and although this is part of the inquiry, in most cases this is probably not the main problem. Powerline noise is well acknowledged and here in Canada, RF pollution stemming from powerline radiation is illegal. Hydro authorities are required to clean-up noisy lines by government mandate (Industry Canada) and seem to react positively to complaints by amateurs. I believe a similar mandate is in play south of the border but because of the vast numbers of hydro operators operating in so many jurisdictions, getting action often seems fraught with difficulty.

The inquiry seems focused on the more nefarious types of radiation sources ... those that are not powerline-related, such as RFI caused by switching power supplies, light dimmers, electric motors, high efficiency lighting, computers, portable electronic devices, wireless routers ... generally any type of device radiating unwanted RF emissions.

Presently, complaints about this type of RF noise to governing bodies or to national associations, mostly seem to go without effective response ... solutions to the problem seem to be left to the amateur to "fix" the offending device or to just "accept it", rather than to put responsibilities on the manufacturers creating the problems. I know personally of amateurs who have just given up the hobby or have moved to the countryside because of impossibly-high illegal noise levels. It seemed as if calls for tighter government controls on electronic device emission-levels, especially on inexpensive and poorly-designed imports, largely from the far east, fell upon deaf ears. Some European jurisdictions found a ridiculous solution to the growing complaints by slackening even further, the allowable 'accepted' levels of spurious emissions. Previously illegal noise-making devices became legal overnight!

In the meantime, noisy electronic devices continue to flood the market at exponential levels ... only now, does the FCC pose this mind-boggling question! Equally stunning is their assertion that "... in search for concrete evidence of increased noise floors, we have found limited quantitative data to support this presumption." Perhaps if they had been maintaining vigilance instead of ignoring complaints when the problems were first reported, they would already have a huge body of the 'quantitative data' they are now seeking.

The Technical Advisory Council Noise Floor Inquiry (ET Docket No. 16-191) is well worth reading for any radio amateurs interested in finding solutions to growing noise problems. The three-page document includes a short list of questions to which responses are sought ... your input is vital, especially if hard data can accompany your comments.

Is it too late to turn the tide? There is no doubt that at this late date,  it will be a huge uphill climb. The public notification document can be found here and the deadline for submissions, which can be made here, is August 11, 2016.