[R-390] R-390 VFO Question

[Barry Scott]

Well, I just found that, on Page 90 of TM 11-5820-357-35, it clearly
states: "The vfo frequency is decreased with a clockwise rotation of the
vfo shaft as viewed from the front panel."

I bet it would be a great idea for me to READ THE MANUAL!

Thanks,
Barry - N4BUQ


On Mon, Sep 16, 2024 at 7:50 AM Barry Scott <72volkswagon at gmail.com> wrote:

> Okay, Larry.  Thanks for the reply.
>
> On further reading, the VFO is a Hartley design and, given that the
> frequency formula for a Hartley is an inverse function of the LC values,
> presuming that at xx 000, the iron core is "out" of the coil and a
> clockwise turn of the KC knob causes the core to be pushed further inside
> the coil increasing the L, then the frequency would indeed drop with CW
> motion of the knob.  Sorry for the awkward way of stating that but I think
> it makes sense to me.
>
> Thanks again,
> Barry - N4BUQ
> Thanks,
> Barry - N4BUQ
>
>
> On Sun, Sep 15, 2024 at 11:10 PM Larry Haney <larry41gm2 at gmail.com> wrote:
>
>> Hi Barry,  You are absolutely correct in your deductions.  When the KC is
>> at its lowest of 000, the vfo is at its highest (3.455 mh).
>>
>> Regards, Larry
>>
>> On Sun, Sep 15, 2024 at 7:23 PM Barry Scott <72volkswagon at gmail.com>
>> wrote:
>>
>>> Looking at the simplified schematic for the 3rd mixer (V205), the output
>>> from the 2nd mixer (V204) tunes from 3 to 2 MC and the VFO tunes from
>>> 3.455
>>> MC to 2.455 MC yielding a constant 455 kc mixer product.  Is it correct
>>> to
>>> interpret those numbers to mean that if the counter starts at XX  000 and
>>> the KC control is rotated CW to XX +000 the VFO's output frequency starts
>>> at 3.455kc and falls 1000 kc for 10 turns CW on the KC knob?
>>>
>>> I'm asking because I want to know what the frequency of the VFO is
>>> supposed
>>> to be when the dial is at XX  000 and I presume it's 3.455 kc but wanting
>>> to make sure.
>>>
>>> Thanks,
>>> Barry - N4BUQ
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>>