• A Fan for the Drake T4X

    07/23/2019 at 11:58 0 comments

    Key Idea:  Run a 12 volt fan on 6 volts for low noise.

    Details:  Get a fan about 3 inches square and tie or bolt it to the back of the final cage.  I used lacing tape, but ty-raps are probably easier.  The lamp behind the frequency scale has one terminal connected directly to the 12.6 VAC filament supply.  Put a single rectifier diode on that terminal.  Put the anode on the terminal and the cathode on the red fan wire.  Ground the black fan wire.  Leave enough slack in the fan wires to get the final cage off without trouble.  The fan runs almost too quiet to hear.

  • Audio Output Transformer for Drake R4A

    06/26/2019 at 18:08 0 comments

    If your Drake R4A (ham radio) has blown its output transformer, a possible replacement is the Hammond 166G6B.  Although nominally the same size as the original, the new transformer is slightly larger and will go above the chassis in front of the can capacitor.  Connect the 120 volt winding in the plate circuit and the 6.3 volt winding to the headphone jack.  If the radio now squeals loudly, reverse the plate circuit leads.

    N.B.  You will have your fingers in high voltage wiring.  Unplug the radio before you do anything.  If you are not comfortable with this work, find someone who is.

    Another Note:  This modification is not intended to "improve" the sound of the radio.  Opinions of how the radio sounds better are as common as elbows.  This mod is to save a fine radio that would otherwise go in the trash. 

  • What Doesn't Cause Sporadic-E Short Skip

    06/04/2018 at 14:28 0 comments

    Today, I decided to investigate whether strong thunderstorms tend to cause sporadic-E clouds in the ionosphere above themselves.  So I looked at the storm data for Okaloosa County, Florida and the stored ionograms for Eglin Air Force Base located in that county.

    In short, no.  Since 2009, a recorded thunderstorm only has about a 20% chance of being associated with a sporadic-E ionogram.  In looking for short skip, the better way is to look in the morning (local) in June, July or August.

    My thanks to the National Climate Data Center, The US Air Force, and Lowell Digisonde for providing the data.