Crystal Radios Of The 2009 (Sprint) Contest Entrants
Lem Morrison, BCB Class (regen)
My receiver was a homebrew Regen using 12DZ6 in double-tuned circuit, coax-fed T antenna.
Mike Tuggle, BCB Class (crystal)
Lyonodyne-17, double-tuned, 12101 3RT detector, two wave traps, RCA Big Cans
Mike Tuggle, Below BCB Class (regen)
Set is same as used in 2009 1AD Contest.
Jack Ivey, BCB Class (crystal)
Equipment is a dual-tuned radio with spider coils of 175/46, Ge diode detector, Bogen matching transformer, modified
balanced armature headphones, with a 250 foot C-shaped antenna about 8 feet above ground, #14 wire.
Kevin Norton, BCB Class (crystal)
Receiver was the "Crystal Commando". This set is a three coil Tuggle set w/cotton basket weaves. The det coil has
ceramic var cap, all others are bakelite. Det. was FO215, w/ series crystal earphones. This set played VERY sharp at times . It can tune the upper part of the band in a wiper less configuration. Despite it's simple design I think the reason it worked so well was due to care in construction (i.e., component spacing and insulation). I wanted to take a step back from big litz and just see how well a simple set could be made to work.
Overall I quite happy with this set.
Ralf 'Brösel' Siemieniec, BCB Class (crystal)
For this years sprint contest I was curious about how my reworked loop antenna crystal radio performs. For this loop
having a spiral loop design, I increased the size to 0.9m x 0.9m. Since the litz wire used before (150 x 0.04 mm) was not that much rugged, I switched to a double silk-covered 270 x 0.071 mm litz wire with an outside diameter of about 2mm. The air variable is a good quality three-ganged device with ceramic insulators, but just one gang is used. Tuning is done with help of a 9:1 vernier dial which is coupled by a plastic extension to the shaft of the variable cap. The air variable cap is isolated against the wooden box while the box itself is mounted head-down on a wooden base. The loop construction is also attached to the base although mounting all things together is a bit more difficult this way.
In difference to all loop antenna sets I know so far I decided to use one of the zero-voltage MOSFETs (ALD110900). The gate is directly connected to the hot end of the tank circuit; the only problem left was how to feed the source. There are basically two possibilities – connect the source via a capacitor or via a coupling coil. After making a simple spice model of the measured characteristics of the MOSFET and doing a number of Pspice simulations I found it is more advantageous to use a coupling coil. After finishing the radio I found that there were some annoying FM ghosts which are probably caught by the coupling loop. To get rid of these I added the FM choke. Matching to the headphones is done by a “Ueberformer” from Dave Schmarder. In the contest, I used a pair of sound powered phones with USIC elements from Dynalec (note that the photo shows my “self-made” phones with rocking armature elements made by Racal. The phones with USIC elements are a bit more sensitive, but the shown phones are very lightweight and comfortable).
The loop does perform very well and is surprisingly sensitive. Selectivity is quite good for a single-tuned unit, especially
at the low end of the band. Tuning is rather sharp, therefore the vernier dial seems to be a “must have”.
What I like most
is the clean sound. I found no distortions so far even in case of strong signals.
Here is a Google map link that you might enjoy viewing.
Robert Weaver, BCB Class (superhet)
-6ME8, 1AD superhet
-30 inch diameter Tuned loop
-Used in the 2009 1AD contest (more info is shown in that section of the website).
Curtis Gamble, BCB Class (crystal)
I just used the two modules with the plexi-glass fronts and no traps.
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