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

[Hubert Miller]

It would seem one of these sources is wrong. In the example i cited, the Xl is ~200K. Your quoted Rs is 10k. This gives a Q of about 20, which is a bit low for quartz, no?
The site i quoted earlier gives these characters for the crystal they are discussing:

"Quartz Crystal Oscillator Example No1
A quartz crystal has the following values: Rs = 6.4Ω, Cs = 0.09972pF and Ls = 2.546mH. If the capacitance across its terminal, Cp is measured at 28.68pF, Calculate the fundamental oscillating frequency of the crystal and its secondary resonance frequency...."

The Rs can vary somewhat. But compare the magnitudes. The ARRL value you quote is >1000 times this value. Something somewhere not right.  I don't have the book. Are you quite sure the 10K
figure, they are not talking about Q ?
-Hue 

-----Original Message-----
From: AKLDGUY . [mailto:neilb0627 at gmail.com] 
Sent: Monday, February 15, 2016 9:31 PM
To: Hubert Miller <kargo_cult at msn.com>
Cc: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] Quick n dirty crystal selectivity - it no workee

> It's near the end of my day, and i'm disinclined to do a lot of work; 
> I'm feeling lazy. But i took a quick look at 
> http://www.electronics-tutorials.ws/oscillator/crystal.html
>
> They work the example of a 10 MHz crystal with an equivalent 
> inductance of
> 2.55 mH and q ~ 25,000. Shure Brothers tell me the Xl for this 
> inductance at
> 10 MHz is ~150k ohm.
> You can see where this is going.
> Now, are you quite sure the Rs of my crystal is 10K ?

As I said originally, the Xl of the inductance negates the Xc of the capacitance, leaving only the resistance. The value of 10K for it was pulled straight from the 1978 ARRL Handbook, page 51.

73 de Neil ZL1ANM


On 2/16/16, Hubert Miller <kargo_cult at msn.com> wrote:
> Last Thanksgiving i sold some heavy metal to a couple mil-vehicle 
> people in Seattle area. One fellow just emailed me he got the BC-654 
> receiver working and he’s going to get a ham license.
> I think that’s just great. They’ll help to keep the interest alive.
>
> -Hue
>
>
>
> From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf 
> Of hwhall at compuserve.com
> Sent: Monday, February 15, 2016 9:01 PM
> To: kargo_cult at msn.com; milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] Quick n dirty crystal selectivity - it no 
> workee
>
>
>
> Sounds like some really good projects! Good luck with the downsizing.  
> Hope it all finds its way to good new homes.
>
>
>
> -Wayne
>
>