[R-390] Honey I Shrunk the VFO (tuning range)

[email protected] [email protected]
Sun, 26 Jan 2003 13:32:31 EST


<PRE>I have read discussions of the R-390 and other Collins VFO 
end-point-adjustment. I wonder if we could all settle on what happens with 
the tuning range? Some people say adding inductance "shrinks" the tuning 
range, others say it "expands" the tuning range. To be correct wouldn't 
adding inductance "shrink" the actual tuning range? If you have a VFO that 
starts out at 0000 and you have to crank it up to +0009 to get exactly 1 MHz 
of change, the VFO tuning range has actually "shrunk". That means with 
exactly 10-turns of the tuning knob, the VFO RANGE of coverage was only 991 
KHz. You will have to "expand" the tuning range so that 10-turns of the VFO 
will cover a full 1 MHz. It sounds counter-intuitive from the numbers on the 
counter dial. When you turn the endpoint adjustment slug clockwise you are 
LOWERING the inductance - thus "expanding" the range of the VFO = it will 
cover more frequency range in the same 10-turns of rotation. Likewise if 
someone has to resort to removing 1-turn or more from the End-Point 
adjustment slug you are lowering the inductance = expanding the tuning range 
of the VFO. Hope I have this right!  73 Todd Roberts WD4NGG.