Wednesday, 1 August 2018

Barn Door CLE Regen Results


This past weekend's 'Barn Door' CLE' saw a lot of participation, in spite of the mid-summer doldrums and the universal nasty lightning noise.


After reading CLE-organizer Brian Keyte's interesting posting to the ndblist, describing his homebrew single transistor regenerative receiver, I was inspired enough to dig out the soldering iron and build one for myself.

The circuit widely described as a '1AD regen' was originally designed several years ago by crystal-radio guru Mike Tuggle out in Hawaii. Mike is widely known for his exquisitely designed "Lyonodyne" DX crystal radio, which inspired an entire decade of intense DX crystal radio building activity back in the late 90's.

Mike Tuggle's 'Lyonodyne' DX Crystal Radio

His  '1 Active Device' medium-wave regen consists of a handful of simple components and a MOSFET that is up to the task. His design was, and still is, being duplicated by many throughout the NDB DX listening community.


Mike's original 1AD regen

Mike recently sent me the circuit diagram that he eventually settled with, showing two possible ways of extracting audio with the widely popular Bogen T725 output transformer.



My own version used Mike's output scheme on the right and the RF circuitry in Roelof Bakker and Steve Ratzlaff's modified version, shown below. I had to increase the tickler (feedback) winding from 4 turns to 11 turns in order to get any regeneration. With 11 turns, my regeneration kicked-in at about three-quarters from the end of the regen control. At some point in time, while testing, some of the leads from my Bogen T725 output transformer momentarily brushed against each other, smoking my FET. Upon replacing it with another BF966, the receiver was much hotter, with regeneration kicking-in very close to the start of the pot. I'm not sure if the first FET was already damaged or that there is enough variation from FET to FET (of the same type) to make some have more gain than others. Accidentally blowing up the FET proved beneficial in the end!



Although most users employ sensitive sound powered headphones with their regens, including myself, some use modern phones with an extra stage of audio, such as an LM386.

Although not nearly as pretty as Mike's regen, my own 1AD was built in an afternoon, just for the recent Barn Door CLE.


My own MW 1AD regen

I later added a calibrated dial plate, breaking the segment from 200kHz to 550kHz into two separate bands, with calibration ~ +/- 1kHz so that I pretty much new where I was tuning at all times. This allowed me to target specific beacons and wait for them to fade up.

When first published, Mike suggested the BF966 MOSFET seemed to work well and I purchased five of them with the intention of someday building a 1AD for the NDB band. The purchase came in handy, as today, the BF966 is no longer available. Apparently the similar, and still available BF998 works well (from tests done by Steve Ratzlaff) but is now in an SMD package at just 18 cents! No doubt there are dozens of MOSFETS that will do the job and at these prices, experimenting with various devices would be a very worthwhile project.

When operating, the regen proved to be surprisingly sensitive, and by using my 10' x 20' loop, I was able to put my local pest (AP-378 kHz and 1/2 mile away) into a deep null so that its huge signal was no longer blocking the top half of the NDB band. The null allowed me to hear beacons within a few kHz of the blowtorch signal as shown below:


------------------------------------------
DD UTC    kHz     Call        Location
------------------------------------------
28 05:15  200     YJ     Victoria, BC, CAN
28 05:15  203     YBL    Campbell River, BC, CAN
28 05:21  214     LU     Abbotsford, BC, CAN
28 11:10  218     PR     Prince Rupert, BC, CAN
28 11:07  221     QU     Grande Prairie, AB, CAN
28 05:30  223     YKA    Kamloops, BC, CAN
28 05:36  227     CG     Castlegar, BC, CAN
28 05:38  230     YD     Smithers, BC, CAN
28 11:04  233     ALJ    Hinchinbrook Island, ALS
28 05:42  236     YZA    Ashcroft, BC, CAN
30 10:06  239     OJ     High Level, AB, CAN
28 05:42  240     BVS    Burlington, WA, USA
30 10:04  241     YLL    Llyodminster, AB, CAN
28 05:44  242     ZT     Port Hardy, BC, CAN
29 11:27  242     XC     Cranbrook, BC, CAN
29 11:26  246     ZXJ    Fort St. John, BC, CAN
30 10:21  248     QH     Watson Lake, YT, CAN
28 05:43  251     YCD    Nanaimo, BC, CAN
29 11:20  254     ZYC    Calgary, AB, CAN
30 09:56  254     SM     Fort Smith, AB, CAN
28 05:50  257     LW     Kelowna, BC, CAN
30 09:54  257     XE     Saskatoon, SK, CAN
28 10:55  260     YSQ    Atlin, BC, CAN
28 05:50  266     VR     Vancouver, BC, CAN
30 09:50  269     ZW     Teslin, YT, CAN
28 05:51  272     XS     Prince George, BC, CAN
28 10:47  283     DUT    Dutch Harbor, ALS
28 06:06  284     FHR    Friday Harbor, WA, USA
30 09:35  284     QD     The Pas, MB, CAN
28 10:39  287     PE     Peace River, AB, CAN
28 06:07  290     YYF    Penticton, BC, CAN
28 06:07  293     MB     Sidney, BC, CAN
28 10:39  295     8C     Fairview, AB, CAN
28 10:39  299     TV     Turner Valley, AB, CAN
28 06:11  312     UNT    Naramata, BC, CAN
28 06:14  325     YJQ    Bella Bella, BC, CAN
28 06:16  326     DC     Princeton, BC, CAN
29 11:08  326     XJ     Fort St. John, BC, CAN
28 06:16  332     WC     White Rock, BC, CAN
28 06:18  338     K      Port Angeles, WA, USA
29 11:06  338     ZU     Whitecourt, AB, CAN
29 11:05  341     DB     Burwash, YT, CAN
28 06:19  344     XX     Abbotsford, BC, CAN
30 09:08  348     MNC    Shelton, WA, USA
28 06:20  350     NY     Enderby, BC, CAN
28 10:25  356     ON     Penticton, BC, CAN
30 09:03  356     ZF     Yellowknife, NT, CAN
28 06:20  359     YQZ    Quesnel, BC, CAN
28 10:20  362     RPX    Roundup, MT, USA
28 10:17  362     BF     Seattle, WA, USA
28 06:22  368     ZP     Sandspit, BC, CAN
29 10:17  368     SX     Cranbrook, BC, CAN
29 10:31  374     EX     Rutland, BC, CAN
29 10:31  375     FS     Fort Simpson, NT, CAN
28 06:20  378     AP     Active Pass, BC, CAN
28 06:26  382     YPW    Powell River, BC, CAN
29 10:37  382     YE     Fort Nelson, BC, CAN
28 06:23  385     WL     Williams Lake, BC, CAN
29 10:39  388     MM     Fort Mc Murray, AB, CAN
28 06:41  389     YWB    Kelowna, BC, CAN
29 10:42  394     DQ     Dawson Creek, BC, CAN
29 10:44  397     ZSS    Yellowhead, SK, CAN
29 10:48  398     YOD    Cold Lake, AB, CAN
28 06:28  400     QQ     Comox, BC, CAN
28 06:28  404     MOG    Montegue, CA, USA
29 10:49  405     2K     Camrose, AB, CAN
29 10:16  406     YLJ    Meadow Lake, SK, CAN
28 06:29  408     MW     Moses Lake, WA, USA
29 10:53  414     8M     Elk Point, AB, CAN
28 20:00  515     CL     Cresent Beach, WA, USA

I ended up with 70 stations logged, including a couple of Alaskans, in spite of the horrendous lightning noise on all three nights. Doing another 'Barn Door CLE' in the middle of the quiet DX season would be much more exciting and several 1AD users have indicated an appetite for such an event. If you put something together please let me know as having an army of 1AD's ready to go would be a great incentive to schedule another Barn Door weekend!

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