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

Sun, 26 Jan 2003 14:29:40 -0500

   Here's my way of reasoning on this; On the Cosmos pto, there are two 
little compensating coils. If the coil has four turns, and you remove one 
turn, the screwdriver adjusting slug will not have as much coil to act upon. 
If you want more "action" with the iron slug, there needs to be more turns. 
In my case , the compensator coil had little range of adjustment. I found 
the solder terminal had enough solder to short out the four turns. There's 
very little room there and its easy for that malfunction to happen. I can 
see where a huge number of pto's could have been made with this weakness.
73's...Steve...KJ8L

>From: [email protected]
>To: [email protected]
>Subject: [R-390] Honey I Shrunk the VFO (tuning range)
>Date: 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.
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