One-Tube Regenerative Shortwave Receiver
AON642830V N-Channel MOSFET General Description Product SummaryVDS30VThe AON6428 uses advanced trench technology toprovide excellent RDS(ON), low gate charge.This device is ID (at VGS=10V) 43Asuitable for use as a high side switch in SMPS and RDS(ON) (at VGS=10V) 8.3. Aon6424.pdf Size:390K aosemi.
Mike Tuggle, WY3B
The subminiature 1AD4 was recommended by Greg Carl (“oL-wooD”) of Flat-‘n-Lo, California as a bustier substitute for the widely used flea-power 6418 submini. While 1AD4 filament current (100 mA) is higher than that of a 6418 (10 mA), its transconductance (gain) is also proportionately higher. Molex Barrier Terminal Blocks SR BTS CS PC 18ASY P datasheet, inventory & pricing. Email to friends Share on Facebook - opens in a new window or tab Share on Twitter - opens in a new window or tab Share on Pinterest - opens in a new window or tab.
This receiver was inspired by a similar one that used a dual gate MOSFET.
(Scroll down in the thread to view the specifics of that set.) The MOSFET set was very prone to hand/body capacitance effects, so this tube version using a surplus BC-221 tuning capacitor with 50-to-1 dial drive was tried. Here’s the schematic:
The subminiature 1AD4 was recommended by Greg Carl (“oL-wooD”) of Flat-‘n-Lo, California as a bustier substitute for the widely used flea-power 6418 submini. While 1AD4 filament current (100 mA) is higher than that of a 6418 (10 mA), its transconductance (gain) is also proportionately higher. So, D-cells power the filament instead of AA’s used for a 6418. The tank tuning coil was wound on a low mu, high Q R40C1 ferrite rod. The number of turns was adjusted to cover from 60 to 25 meters (4.2 to 12.3 MHz). My thought on the tickler was to wind as many turns as I could get on the sliding tube. If too many turns, I’d slide the tickler away from the main winding. As it turns out the tickler works nicely up near the main winding. How’s that for scientific reasoning ? I did the same for the A-G link on the other end.
I was pleasantly surprised when it worked right off the bat. That doesn’t happen often for me. Some body-capacitance effects were still there, but MUCH reduced from the MOSFET SW set. The BC-221 metal front panel probably helps with that problem. Screen grid regeneration control is exceptionally smooth. It eases seamlessly into and out of oscillation.
After a quick calibration using six points from a signal generator, I set the dial to where the calibration said 8420 kHz should be. Bingo ! There was WLO (Mobile, AL) bigger than life. That’s when I really began to like this radio. DX possibilities are “worldwide.” The following distances have been heard:
The antipodal (half globe) distance is 12,346 miles. Of course, these are high power (100 kW+) operations, but I’m starting to hear lower power (10 kW +/-) stations in South America, notably Brazil and Colombia.
The question arose early on: How well does the set perform on just the ferrite rod coil as a loop antenna ? Turns out, not very well. It was just too weak to make out anything. The MOSFET version wasn’t all that great without an outside wire, either. Both sets need that outside wire to the world. However. for its mellow behavior, I’m beginning to think the 1AD4 tube version is my number one SW set. It’s nice to be able to turn it on any time day or night and look to hear a whole new adventure.
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