The Heathkit MR-1010

 The MR-1010 was a very cool radio for the AM band as well as LF.  It had some interesting design features with a digital frequency display, a multi-section ceramic filter, MANUAL gain control (sensitivity) with a signal strength meter.  And of course a rotating antenna for direction finding.

One neat design feature is the simple/elegant way in which the rotating antenna is mounted.  A 1/4 inch phone plug (actually stereo) is mounted vertically in the plastic antenna assembly.

  The corresponding phone jack is mounted on the top of the receiver itself.

  The round antenna assembly is then simply plugged into the receiver and it can rotate freely 360 degrees without stops.

I don't know who originated this antenna mount but it appears that all manufacturers of radio direction finder receivers used this same idea.

There are some parts of the MR-1010 that aren't super great.   The frequency readout uses those high voltage discharge displays, similar to the ones in the SB-104.  The DC-DC power supply in mine "sings", I'm assuming a bad capacitor.  And I just noticed that the display is kaput so maybe the repair/replace will be the subject of another blog post.   The radio has a built-in battery holder for D-cells but on mine the fit was so tight that I had a hard time getting the cells out of the plastic tube.  The 2 pin connector for DC power is somewhat hard to find.

  Although the display is digital the tuning cap is driven with a mechanically complex string/spring/pulley system similar to one in a slide-rule dial receiver.

But those are all quibbles.  The real problem is that AM radio (and LF for that matter) just isn't worth listening to anymore.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm