[ARC5] Some info on the S-38

[Fuqua, Bill L]

  Could be, our language changes all the time, I want to buy a sandwich and they as if I want white or wheat.
But both are wheat bread. I think most don't know there is a pair of poles per resonant device or RLC.
73
Bill wa4lav

________________________________________
From: Dennis Monticelli [dennis.monticelli at gmail.com]
Sent: Sunday, November 22, 2015 11:30 PM
To: Fuqua, Bill L
Cc: Richard Knoppow; arc5 at mailman.qth.net
Subject: Re: [ARC5] Some info on the S-38

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<mailto: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<mailto:arc5-bounces at mailman.qth.net>] on behalf of Richard Knoppow [1oldlens1 at ix.netcom.com<mailto:1oldlens1 at ix.netcom.com>]
Sent: Friday, November 20, 2015 2:51 PM
To: arc5 at mailman.qth.net<mailto: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
>
>
>
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--
Richard Knoppow
1oldlens1 at ix.netcom.com<mailto:1oldlens1 at ix.netcom.com>
WB6KBL

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