[Milsurplus] Quick n dirty crystal selectivity - it no workee

[AKLDGUY .]

ARRL Handbook:
1963 Edition (page 52) says the equivalent resistance is
'of the order of a few thousand ohms'.
1975 Edition (page 51) says the same.
1978 Edition (page 51) says 10K upwards.
1992 Edition (page 2-55) says 'Typical values...range from 10K and higher.'

All of these earlier sources point out that the inductance of the L is very
high, several Henries, and that this results in a high Q.

However, in the 1995 Edition (page 14.24) we see a small chart giving
typical values ranging from 340 ohms for a 1MHz crystal to 7 ohms for
a 10MHz fundamental type.

Something is not right. Why is there such a huge discrepancy?

73 de Neil ZL1ANM



On 2/16/16, Hubert Miller <kargo_cult at msn.com> wrote:
> "Series Resistance
>
> Series resistance is the effective resistive component in series with the LC
> model of the crystal itself (see Figure 1). Oscillator circuits can tolerate
> some degree of series resistance, but not too much. A typical range is 25Ω
> to 100Ω for most crystals. The crystal vendor usually characterizes this
> resistance and specifies typical or maximum values for series resistance.
> Excessive crystal series resistance can lead to oscillator startup failure,
> so sufficient margin must be built into the oscillator design.
>
>
>
> An exception to the above guideline is 32.768kHz wristwatch crystals, where
> series resistance can be in the tens of kilohms. Consequently, for this
> application the oscillator circuit must accommodate this high series
> resistance. Failure to address this will result in a 32.768kHz oscillator
> that does not oscillate. You should not expect to use an oscillator designed
> for a 10MHz crystal with a 32.768kHz crystal. It will not work."
>
>
>
> Quoted from:  https://www.maximintegrated.com/en/app-notes/index.mvp/id/726
>
>
>
>
> I can see that since i don’t know the ESR of the crystal i put into the
> Command Sets receiver cathode, and it is shunted by something like a 300 ohm
> resistor, it looks like i will need an RFC in series
>
> with the resistor to  have the crystal ‘work’ as a selective bypass.
> Otherwise the low resistance of the cathode resistor just negates the
> crystal.
>
> -Hue
>
>