Friday, 5 September 2014

Tuggle-Style LF Regens

If the name sounds familiar, you may recognize it from reading about the DX crystal radios that Mike Tuggle has created over the past several years. Some might even say that his state-of-the-art and very elegant "Lyonodyne 17" crystal radio re-kindled the modern day interest in crystal radio DXing, once the mainstay of all radio adventures.
Mike Tuggle's Lyonodyne 17 Crystal DX Tuner
I'm not sure what sparked Mike's interest in building regens but it may go back several years to the "1AD" contest sponsored by the Birmingham Crystal Radio Group. This was a DX contest challenge that allowed a receiver to use only "1 Active Device", as explained in the rules:
"Only one active device is allowed to be counted to get the 1AD bonus points. The device can be a bipolar, FET, tunnel diode or tube (triode, tetrode, pentode, or heptode), but only one device may be used. If a tube envelope has more than one tube in it, use only one of those active devices to be counted as a 1AD. Crystal sets may be used if one active device is added either inboard or outboard. Totally passive crystal sets are not allowed. In the active set, any number of diodes (either solid state or tube diodes) may be used; however, a tunnel diode or similar active device counts as the 1AD for the contest.
The use of integrated circuits can be interesting in that one IC can be used to build a full superhet. The use of an IC means that the set will not qualify for the 1AD nor for the 2AD bonus points."

The challenge was too hard to resist for many and the contest was popular for several years running. Some of the inventive entries for individual years may be seen here. The contest logbooks  also make for interesting reading and demonstrate the capability of some of these simple radios.

Although the contest has not been run for the past few years, there is still much interest and discussion of "1AD" radios on Dave Schmarder's "RadioBoard" forum.

Mike's LF tuner is a prime example as he uses it daily and continues to post some amazing DX to the Yahoo "ndblist" Group. His furthest ndb catch in North America with the regen has been "YY" in Mont Joli, Quebec.
Now, "YY" is a good catch for me, from B.C., but Mike is listening from Kaneohe, Hawaii !

You can read about Mike's original design here, while his latest version shown below, incorporates a dedicated LF antenna tuner.

LF Regen (Courtesy Mike Tuggle)

LF Regen Schematic (courtesy Mike Tuggle)
A recent posting to the ndb list by Roelof Bakker(PAØRDT) of mini-whip prominence, described his recent construction of his own LF regen, based largely on Mike's design but with a few interesting changes.

Courtesy: Roelof Bakker, PAØRDT

Roelof has also published a nice write-up describing the project which sparked a lot of "must build" discussion within the group.....even enough to make Mike get out his soldering iron and build the European-version!

As old and as simple as they are, regenerative receivers still hold much fascination amongst radio builders and dollar-for-dollar are amazingly good performers, especially on LF.

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