[ARC5] Some info on the S-38

[Dennis Monticelli]

They probably mean one pole-pair per rock.

Dennis AE6C

On Fri, Nov 20, 2015 at 12:23 PM, Fuqua, Bill L <wlfuqu00 at uky.edu> wrote:

>   Speaking of crystal filters.
> A LC resonator has two poles as does a crystal.
> Why is it that when describing crystals filters they speak of one pole per
> crystal.
> 73
> Bill wa4lav
>
> ________________________________________
> From: ARC5 [arc5-bounces at mailman.qth.net] on behalf of Richard Knoppow [
> 1oldlens1 at ix.netcom.com]
> Sent: Friday, November 20, 2015 2:51 PM
> To: arc5 at mailman.qth.net
> Subject: Re: [ARC5] Some info on the S-38
>
>     I didn't differentiate the purposes of the filters.  Yes, the
> filters used in carrier systems were to isolate the channels and allow
> closer spacing (more channels).  Up to at least 20 Mhz atmospheric noise
> dominates any other source in most receivers, even rather noisy ones.
> There is a tremendous amount of technical literature about this. Some of
> the older noisy RF tubes, like the 6K7 and 6SK7 have better dynamic
> properties than lower noise tubes so are advantageous where the very
> minimum receiver noise is not necessary.  I think this is one reason the
> familiar 6BA6 continued in wide use after much quieter tubes became
> available; it has better cross modulation/ intermodulation
> characteristics. I discovered this years ago when experimenting with low
> noise input stages for communications receivers.  Sometimes the plain
> vanilla kind works best.
>
> On 11/20/2015 10:43 AM, Fuqua, Bill L wrote:
> >    If you have an antenna sufficient to hear atmospheric noise on HF
> that is the best you can  do other than improving the effective noise
> bandwidth of the receiver.
> > That is why the application of low noise figure devices are not common
> or necessary in HF receivers. The atmospheric noise becomes the limiting
> factor.
> > Microwave systems using frequency division multiplex systems used many
> pole filters not due to noise issues but for isolation between adjacent
> voice channel rejection.
> > You can still find very good mechanical filters used in these systems
> from time to time. It is just that they are at odd frequencies for amateur
> use and are relatively wide
> > in bandwidth.
> > 73
> > Bill wa4lav
> >
> >
> >
> > ______________________________________________________________
> > ARC5 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/arc5
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:ARC5 at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
>
> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
>
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>