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Monday, October 31, 2011

Pumpkin Pi and JBOT Gremlins

Maria wanted to go with a mathematical theme for this year's Jack-0-Lantern. Pumpkin Pi!

I have been chasing some gremlins and banshees around my old Azores 17 meter DSB rig. The JBOT Amp worked fine into a dummy load, but of course things got a bit more complicated when I put it into the rig and connected it to an antenna. It would take off (like a banshee!) if the load was at all reactive. I think this is the result of inadequate shielding and inputs a bit too close to outputs. But it all settles down nicely when I put a transmatch in the antenna line and tune out the reactance. I may just leave it this way.

Output is a bit low -- only about 1 Watt. I realize that at 18 MHz output should be dropping a bit, but I think I should be getting more. I THINK I'm giving it the recommended 1 milliwatt input. At some point I think Farhan mentioned the possible need to experiment with the number of turns on the secondary of the output transformer....

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2 comments:

  1. Tell Maria that where I work here in Nebraska, we have a party on PI day every year. A couple years back I was asked by the accounting department if I wanted to participate in 'PI' day with them as my last name has PI in it.
    PIATT or PI-@ (I use PI sign).
    it is also important that one should remember in the movie 'notime for sargents' we learned that "Pie are round, Cake are Square" :)
    Dar Piatt - W9HZC.

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  2. Hi Bill,
    A while back I built a JBOT and left a video on YouTube.
    http://www.youtube.com/watch?v=rID2-uZrCgE
    Tom, ak2b

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