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'.

Back To The Magic

The magic band has always had a strong pull on me, ever since being put under its spell in the late 60s. I quickly learned that the surest way to guarantee a band opening was to leave the house for a few hours. Invariably when returning, the other local 6m addicts would gleefully describe everything that you had ‘just missed’. The 6m gods were rarely forgiving and this unfailing behaviour became part of the band's mystique.



This odd love-hate relationship continues to this day but with the FT8 mode being used almost exclusively now on 6m, it’s your computer that now snickers at you for any untimely excursions from the shack ... showing you, in any delightful color scheme that you choose, all of the DX that you 'just missed' once again!

It happened to me again yesterday, while out in the yard stacking next winter's firewood.

It was just a short excursion, as the eastern stations were working Europeans and all of the VE4 beacons were very loud back here on the coast. The possibilities of a link to the European path kept my excursion to only 10 minutes but sure enough, there it was on my WSJT-X list of decodes .... several CQs from CT7ANG in Portugal! My laptop could barely stop giggling. This would have been the first PNW-EU QSO of the summer had I been maintaining vigilance!

163315 -14 0.1 738 ~ CQ CT7ANG IM67
I continued to stack firewood and to watch the band more closely, knowing that every once in awhile, for entertainment purposes, the prop gods will toss out a bone or two, just to keep you on the hook.

A later check indicated that CT1HZE’s CQs had been decoded just a few moments earlier ... there was renewed hope!


185100 -2 0.2 2134 ~ CQ NA CT1HZE IM57

Joe’s strong FT8 CQ popped-up again a few minutes later and he came right back to my initial call. Although that was it for the day, the 2019 PNW-EU path had begun!

courtesy: PSK Reporter

I’m still somewhat ambivalent about FT8 and its ‘coldness’ when it comes to person-to-person interaction, but since most of the DX action on 6m is now digital, it’s either embrace it or miss out. At the moment, I’m at least prepared to hug it and see how it behaves. If it puts more Europeans and new DXCCs into my magic band log, then that’s a worthwhile investment.

Unlike way too many others, I’m not prepared to let my computer endlessly CQ for hours at a time. In a crowded local environment, with big strong signals being the norm, this method of operating is simply disrespectful to other amateurs as this mostly useless CQing will usually make reception of any weaker signals impossible.

FT8 is a weak-signal mode and the interfaces used do not handle extremely strong local signals very well. I would urge others to think about this poor operating practice and adopt what has always proved to be the best tactic for catching DX ... listen, listen, listen. The same tactic works just as well on FT8 as it does on CW.

Back to stacking firewood but having tossed me a bone yesterday, I’m sure the prop gods will be out to get even for awhile!

The Enigmatic Heathkit CR-1 Crystal Radio

For the past several months my interest in ‘DX-crystal radio’ construction has been percolating once again. It began when I ran across an interesting description of Heathkit’s legendary CR-1, a double-tuned good performer and very much sought-after by collectors as well as by users. The article described one homebrewer’s attempt to duplicate the receiver and to learn more about the detector and antenna tuning ferrite-loaded coil's secrets.


When it comes to crystal radios, there is nothing revolutionary regarding the CR-1’s basic circuitry but for some odd reason, it has achieved cult-like status as well as high dollar value.

courtesy: Scotts Crystal Radios

I've been eager to get my mitts on one to see how it performs after reading of one DXer's fifty-eighth catch with his own CR-1!

The article that piqued my interest appears on 'Scott's Crystal Radios' website and makes for an inspirational read, eventually revealing the inside core arrangement of the ferrite-loaded tuned circuits via an actual X-ray of the device! By the way, if you are looking for a nice set of older headphones, Scott's website is the place to visit!

courtesy: Scott's Crystal Radios

Scott was eventually able to achieve performance equal to that of his borrowed CR-1, with his own slightly modified versions, all in a similar-sized footprint. Perhaps this is one reason why the CR-1 is so much sought-after, as good performance in a very small package is not the norm when it comes to crystal radios. It's usually a case of ‘the bigger, the better’ when it comes to performance.


A recent search of my junque box revealed several NIB ferrite loopsticks that would allow a potntial reproduction of this interesting circuit.

Several years ago I spent an eye-opening winter learning about DX crystal radios as up to that time I had always believed it would be impossible to hear anything other than strong local signals on a crystal radio. I quickly discovered that there was a very large Crystal Radio Yahoo Group where members were working at the leading edge of crystal radio design. I also found that the group sponsored an annual Crystal Radio DX Contest which inspired me to dig deeper.

It wasn’t too long before I decided to join the fun and attempt to build a crystal radio DX-machine but I was in for a few surprises and a long learning curve ... it seemed that hearing broadcast band ‘DX’ on a crystal radio (anything other than loud locals) was not going to be an easy task!

Over the course of several months I tried many types of variable capacitors, tank coil configurations and antenna tuning circuits. I even erected a dedicated antenna system for the various experimental circuits I was putting together ... an 'Inverted-L', 50’ straight up and 70’ horizontal, along with a ground rod connected to several buried radials.

I quickly learned about something I normally didn’t have to worry about when working with ‘active’ devices and that was overcoming system and component losses. In critical crystal radio design, it’s all about minimizing the losses in every stage and every component in the system since there are no amplifiers to help overcome these losses. Your system is only as good as the weakest link. In true crystal radio DXing, no active devices are permitted ... it’s just your crystal radio and the energy generated at some, hopefully far away, transmitter site!

After several months, I eventually ended up with a well-performing triple-tuned set that used lots of 'trapping' because of all of the very strong nearby signals here ... eight 50kW locals!

A description of the learning curve, with several do's and dont's to help new builders, can be found on my website here.

Back then, 80 stations were logged (from my location on Mayne Island in SW British Columbia) over the one-week Crystal Radio DX Contest.


CRYSTAL RADIO LOGBOOK

FRQ	STATION	LOCATION	POWER
540	CBK	WATROUS, SK	50KW
550	KARI	BLAINE, WA	2.5KW
560	KPQ	WENATCHEE, WA	5KW
570	KVI	SEATTLE, WA	5KW
580	KFXD	NAMPA, ID	5KW
580	KTMT	ASHLAND, OR	1KW
600	CKBD	VANCOUVER, BC	10KW
650	CISL	VANCOUVER, BC	10KW
670	KBOI	BOISE, ID	50KW
690	CBU	VANCOUVER, BC	50KW
730	CJNW	VANCOUVER, BC	50KW
750	KXL	PORTLAND, OR	20KW
770	CHQR	CALGARY, AB	50KW
780	KKOH	RENO, NV	50KW
790	KGMI	BELLINGHAM, WA	1KW
800	CKOR	PENTICTON, BC	500W
800	CHAB	MOOSEJAW, SK	10KW
810	KGO	SAN FRANCISCO, CA	50KW
820	KGNW	SEATTLE, WA	5KW
830	CKKY	WAINRIGHT, AB	3.5KW
840	KSWB	SEASIDE, OR	500W
840	CKBX	100 MILE HOUSE, BC	500W
850	KOA	DENVER, CO	50KW
860	KPAM	TROUTDALE, OR	10KW
870	KFLD	PASCO, WA	250W
880	KIXI	MERCER ISLAND, WA	10KW
880	COOL	EDMONTON, AB	50KW
890	CJDC	DAWSON CREEK, BC	10KW
900	CKMO	VICTORIA, BC	10KW
910	CKDQ	DRUMHELLER, AB	50KW
920	KXLY	SPOKANE, WA	5KW
930	KBAI	BELLINGHAM, WA	500W
940	CJGX	YORKTON, SK	50KW
950	KJR	SEATTLE, WA	50KW
960	CFAC	CALGARY, AB	50KW
980	CKNW	NEW WESTMINSTER, BC	50KW
1010	CBR	CALGARY, AB	50KW
1040	CKST	VANCOUVER, BC	50KW
1060	CKMX	CALGARY, AB	50KW
1070	CFAX	VICTORIA, BC	10KW
1090	KYCW	SEATTLE, WA	50KW
1130	CKWX	VANCOUVER, BC	50KW
1160	KSL	SALT LAKE CITY, UT	50KW
1170	KPUG	BELLINGHAM, WA	5KW
1180	KOFI	KALISPELL, MT	10KW
1190	KEX	PORTLAND, OR	50KW
1200	WOAI	SAN ANTONIO, TX	50KW
1210	KBSG	AUBURN, WA,	10KW
1210	KZTS	SUNNYSIDE, WA	1KW
1240	KGY	OLYMPIA, WA	1KW
1240	KOFE	ST. MARIES, ID	500W
1250	KKDZ	SEATTLE, WA	5KW
1250	KWSU	PULLMAN, WA	5KW
1260	CFRN	EDMONTON, AB	50KW
1260	KLYC	McMINVILLE, OR	850W
1270	CHAT	MEDICINE HAT, AB	10KW
1270	KTFI	TWIN FALLS, ID	1KW
1280	KIT	YAKIMA, WA	1KW
1290	KGVO	MISSOULA, MT	5KW
1290	KUMA	PENDLETON, OR	5KW
1290	KKSL	LAKE OSWEGO, OR	5KW
1300	KOL	SEATTLE, WA	5KW
1300	CJME	REGINA, SK	10KW
1310	CHLW	ST. PAUL, AB	10KW
1320	CHMB	VANCOUVER, BC	50KW
1340	KLKI	ANACORTES, WA	1KW
1360	KKMO	TACOMA, WA	5KW
1370	KAST	ASTORIA, OR	1KW
1410	CFUN	VANCOUVER, BC	50KW
1470	CJVB	VANCOUVER, BC	50KW
1510	KGA	SPOKANE, WA	50KW
1520	KKSN	OREGON CITY, OR	15KW
1530	KFBK	SACRAMENTO, CA	50KW
1550	KCCF	FERNDALE, WA	10KW
1590	KLIV	SAN JOSE, CA	5KW
1600	KVRI	BLAINE, WA	10KW
1620	KYIZ	RENTON, WA	1KW
1640	KPBC	LAKE OSWEGO, OR	1KW
1660	KXOL	BRIGHAM CITY, UT	1KW

Old notes indicate that there were 14 stations at S9 or higher, requiring heavy trapping to hear anything close to their frequencies. 

My recent interest made me wonder what the situation is today when it comes to the number of strong local ‘blowtorch’ signals, surely the bane of all crystal radio DXers? Although there have been a few changes over the years, a quick scan of the band during the prime DX evening hours found that although one of the blowtorch signals (at 600kHz) was now gone, another had appeared at 1200kHz ... sadly no net difference. The top end of the band, always a prime area for good skywave DX, is unfortunately still dominated by a huge signal from KVRI just across the water near the Canadian / U.S. border. If KVRI were silent, the top end would be a wonderfully quiet hunting-ground for new catches. The new local blowtorch (CJRJ) on 1200 kHz will now cause problems for the middle of the band, which was always a good region for DX. So it seems overall, there hasn’t been a huge change here other than in the middle of the band. It looks as though there are still some good watering-holes to be had but several traps will still be needed in any new system. Once my present radio-bench project is finished (a '36 RK-39 crystal power oscillator) I’m looking forward to more research and design of a couple of new systems, starting with something similar to the CR-1 as well as some experimentation with toroidal coils. I always find the research and planning phase of any new project more interesting and fulfilling than the actual construction and implementation! Hopefully I’ll have something ready for the fall DX season! Thanks to VA7MM, I will also have the loan of an original CR-1 next winter to make comparisons to any clone that I might build! If building a DX-crystal radio is something that might interest you, there are several great websites offering inspiration and helpful info. The links for these may be found at the bottom of my own crystal radio page. As well, there are two active crystal radio groups on Facebook, where daily two-way discussion can be had. Perhaps, with enough new interest, we can even revive the annual Crystal Radio DX Contest!