[AMRadio] HRO Coil Compatibility

[JAMES HANLON]

Brian,
 
Coils from any series of the HRO up through the 7 can be interchanged and expected to work.  That includes individual coil sections as well as the four-coil assembly.  The HRO-50 used a lower jack-bar on the receiver side of the interface, so if you are going to plug in coils from an earlier vintage radio into the '50, you should put washers in between the coil assembly and the aluminum coil shield to lower the coil assembly a little.  I did that with an HRO-7 AC (15 meter) coil set that I have used in my HRO-50 since 1951, and it is still working fine.  I recently acquired an HRO-50-R1 at a hamfest for free!  but there were no HRO-50 coils to go with it.  The fellow did have a bunch of coils from the pre-war era, however, so I took along a full set of them, A, B, C, and D ranges.  After I added the above mentioned washers, I aligned them in the new 50-R1 and they work fine.  The HRO-60 goes to dual conversion on the C, B, and A coil sets, so they are not compatible with earlier HRO's, but the lower frequency coils from the '60 are cross compatible.  
 
How did you melt that oscillator coil?
 
Jim Hanlon, W8KGI