[Elecraft] Re: K2 Builder Alert: R19 on RF board wrong value

[Wayne Burdick]

James Hammons wrote:

> Seems to me, if you have enough range without the added R19 it
> would be better to leave it at 10k.

Even if you have enough reference oscillator tuning range without adding R19,
you might still want to add it. It will allow you to tune significantly below
160 meters (into the AM band) while preserving VFO tuning linearity. The high
end of the AM band is an interesting place -- try listening at night!


> With the BFO now showing less drift than the PLL ref osc, I am
> wondering if could not also be improved a little bit more using a
> toroid on a T44-7 core like the BFO?

In nearly all cases, the answer would be no. The inductor used in the reference
oscillator already has a decent temperature coefficient, and the drift here is
dominated by the varactor diodes. In fact we tried this and found that the
higher Q of a toroid at this location could actually be detrimental.

We're testing some special capacitors (N750) which may provide a slight
additional improvement. We'll post results once we've tried them.

73,
Wayne
N6KR