[ARC5] Making Stable Inductors for 2 MHz

[J. Forster]

Hi Ken,

> On 29 Jun 2011 at 10:13, J. Forster wrote:
>
>> Do you know if it makes much difference whether the winding is a single
>> layer solenoid, or if it needs to be like IF transformers, as long as
>> the self-resonant frequency is high enough?
>
> For frequencies down to 500 Khz, single-layer is both more stable,
> and more easily done. It is also quite, quite adequate. One other
> thing to keep in mind: the lower in frequency you build your VFO for,
> generally, the more stable.
>
> If you are still very concerned about stability, you might consider
> building your VFO for 1Khz or even 500 Khz, then doubling or
> quadrupling.

Too complicated, IMO. I need good, but nothing like exceptionsal,
stability. +/- 5 KHz / 2 MHz will do fine.

> One significant advantage to doubling is that the output of your VFO
> at the frequency of interest usually has no effect on stability
> caused by feedback to the input.
>
>> From what I can see, most (toroid-cored VFOs) are not that good.
>
> Yet, there have been many, many VFOs built using toroids, and almost
> all for higher frequencies, like up to 15 MHz, at least. The key is
> VERY low current through them, and minimal levels of RF.
>
> Nonetheless, for your uses, I would avoid them. They are unnecessary.
> One of their most useful characteristics is their very small
> size...which in your case is not needed.
>
>> > filament (heat) vastly reduces any thermal drift.
>>
>> Understoof. I want to avoid any temperature control, hence the +/- 10
>> C spec. I think, since the thing will eventually be in the center of a
>> 50,000 ton ship, the temperature will be pretty stable.
>
> I see absolutely NO PROBLEM with a simple, single-layer solenoid-type
> coil and variable capacitor VFO in that application.

Well, the cap will be fixed and permanently trimmed to frequency.


> Good luck, John.
>
> Ken

Thank you,

-John

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