Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-me06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 5CA6D38000099; Wed, 11 Jul 2012 15:39:25 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Sp2k6-0002MM-Hn for rs_out_1@blacksheep.org; Wed, 11 Jul 2012 20:38:34 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Sp2k5-0002MD-RK for rsgb_lf_group@blacksheep.org; Wed, 11 Jul 2012 20:38:33 +0100 Received: from imr-db03.mx.aol.com ([205.188.91.97]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1Sp2k2-0005K7-Lp for rsgb_lf_group@blacksheep.org; Wed, 11 Jul 2012 20:38:32 +0100 Received: from mtaomg-ma06.r1000.mx.aol.com (mtaomg-ma06.r1000.mx.aol.com [172.29.41.13]) by imr-db03.mx.aol.com (8.14.1/8.14.1) with ESMTP id q6BJcGsI010218 for ; Wed, 11 Jul 2012 15:38:16 -0400 Received: from core-msd002c.r1000.mail.aol.com (core-msd002.r1000.mail.aol.com [172.29.234.5]) by mtaomg-ma06.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 8DA11E000095 for ; Wed, 11 Jul 2012 15:38:16 -0400 (EDT) References: , <4FFC3518.1030405@xs4all.nl>, <4FFD5313.6103.333D978@mike.dennison.ntlworld.com> To: rsgb_lf_group@blacksheep.org In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: Markus Vester X-MB-Message-Type: User X-Mailer: Webmail 36478-STANDARD Received: from 77.7.37.232 by webmail-m156.sysops.aol.com (64.12.159.1) with HTTP (WebMailUI); Wed, 11 Jul 2012 15:38:15 -0400 Message-Id: <8CF2DB3D98F0811-2624-787AF@webmail-m156.sysops.aol.com> X-Originating-IP: [77.7.37.232] Date: Wed, 11 Jul 2012 15:38:16 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20110426; t=1342035496; bh=cEAHuA7UbWUBYCsLEoGaslhmhJybG0wu6HQJOf58FLE=; h=From:To:Subject:Message-Id:Date:MIME-Version:Content-Type; b=pBpnSdgP9G2Vq4Nvw5AYOauY8RW248fHMwFe16ntvUgkmG9BGLGdoke1E8u65gWOk fJWIT5W9IQy5MR/v9qCyxkCSnrQEq/IvBxyu+RrANWYUWuI84NJr7FX9ZhN/89r875 19T3lyPyZBMqxEO39kW4aeOP7EdsIXAjJiA+DGsY= X-AOL-SCOLL-SCORE: 0:2:464741952:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Graham, Mike, given the ratio of occupied signal bandwidth (a few Hz) to filter bandwidth in question (a few 100 Hz), I don't believe there will be any significant impact of analog filters on signal shape. Neither on background noise, directly. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [205.188.91.97 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 14e68a9cb6dee915a96310ea9bf261c5 Subject: Re: LF: OPERA Question Content-Type: multipart/alternative; boundary="--------MB_8CF2DB3D9A21311_2624_1F3A77_webmail-m156.sysops.aol.com" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=CASHCASHCASH, HTML_FONTCOLOR_UNKNOWN,HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:480668480:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m412.1 ; domain : mx.aol.com DKIM : pass x-aol-sid: 3039ac1d608e4ffdd66c029f X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ----------MB_8CF2DB3D9A21311_2624_1F3A77_webmail-m156.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Hi Graham, Mike, given the ratio of occupied signal bandwidth (a few Hz) to filter bandwidth= in question (a few 100 Hz), I don't believe there will be any significant = impact of analog filters on signal shape. Neither on background noise, dire= ctly. However in the presence of impulsive noise, eg lightning statics, the effec= tiveness of a noiseblanker will be severely degraded if the duration of the= pulses is prolonged by narrow filters with long ringdown. The sharper the = better - especially at VLF where spherics are dominated by the short cracks= from return strokes. However strong carriers should be excluded from the p= assband before noiseblanker action, as otherwise they will be contaminated = by sidebands from the cutouts. Best 73, MArkus (DF6NM)=20 -----Urspr=C3=BCngliche Mitteilung-----=20 Von: Graham An: rsgb_lf_group Cc: james.moritz Verschickt: Mi, 11 Jul 2012 4:15 pm Betreff: Re: LF: OPERA Question ''At first glance it appears crazy'' Mike, Welcome to the crazy world of JR ! The basic explanation is the narrow filters increase the noise power= =20 n a limited bandwidth , ringing due to the Q , similar to CW , narrow= =20 ilters tend to round the CW signal The DSP engine is better equipped to differentiate between carrier and= =20 oise and has a much greater dynamic range , so optimum results are= =20 btained , when the signal is presented to the interface, as close to to= =20 he original as possible , the DSP filter profiles are tailored to the= =20 ode/speed in use This can be noticed with the new generation of SDR support software = ,=20 here audio/voice recovery can be superior to conventional hardware=20 ased systems With hardware filtering , there are transit (group) delays which can=20 lter the amplitude / time , either from on/off keying or with FSK,= =20 his can be observed when sending wide band FSK , although the audio= =20 evel remains constant and 'phase continuous' , its possible some times= =20 o see a 'am modulation' envelope on the carrier ... $$$$ can=20 olve this problem , but for most Ham kit its something that=20 happens' Physical constraints , if there is a very large carrier in the pass= =20 and and this is pushing the hardware into non-linearity / A/D to=20 ver range , giving quantising errors, then , yes filtering would=20 elp , but its more likely its the analogue path that's causing=20 ntermod products .....reducing the rf/if gain will provide the solution I think that's about the picture , if Jim's about , im sure he will= =20 ill in the gaps 73 -G.. ------------------------------------------------- rom: "Mike Dennison" ent: Wednesday, July 11, 2012 10:18 AM o: ; ubject: Re: LF: OPERA Question >> Narrow IF filters are not desirable and reduce the > performance of the demodulator , better simply use SSB filter > GL ..73 -G.. Graham, Why is that the case? What does the considerable extra bandwidth achieve? Is the SSB bandwidth optimal, or would it be even better with 10kHz bandwidth, or 100kHz?. Why is 3kHz better than perhaps 1kHz or 2kHz? At first glance it appears crazy to let in all sorts of adjacent channel QRM (the bandwidth is more than ten times the size of the entire Opera window) when using a mode that occupies a fraction of 1Hz. Is it simply that the 1.7kHz Tx tone is high enough for the SSB filter to kill its harmonics, and on receive it is difficult to get a 1.7kHz tone out of a CW filter, even with passband shifting. Am I missing something? 73 de Mike, G3XDV g3xdv.blogspot.co.uk =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 ----------MB_8CF2DB3D9A21311_2624_1F3A77_webmail-m156.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Hi Graham, Mike,
 
given the ratio of occupied signal bandwidth (a few Hz) to filter band= width in question (a few 100 Hz), I don't believe there will be any signifi= cant impact of analog filters on signal shape. Neither on background n= oise, directly.
 
However in the presence of impulsive noise, eg lightning statics, = ;the effectiveness of a noiseblanker will be severely degraded if the = duration of the pulses is prolonged by narrow filters with long ringdo= wn. The sharper the better - especially at VLF where spheric= s are dominated by the short cracks from return strokes. How= ever strong carriers should be excluded from the passband before noise= blanker action, as otherwise they will be contaminated by sidebands fr= om the cutouts.
 
Best 73,
MArkus (DF6NM) 


= -----Urspr=C3=BCngliche Mitteilung-----
Von: Graham <g8fzk@g8fzk.fsnet.co.uk>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Cc: james.moritz <james.moritz@btopenworld.com>
Verschickt: Mi, 11 Jul 2012 4:15 pm
Betreff: Re: LF: OPERA Question

''At f=
irst glance it appears crazy''

Mike,

Welcome to the crazy world of  JR  !

The  basic  explanation is the  narrow filters  increase the  noise power=
=20
in a limited   bandwidth , ringing  due to the  Q , similar to  CW , narrow=
=20
filters tend to  round  the  CW signal

The DSP  engine  is  better equipped to  differentiate between  carrier and=
=20
noise and  has a  much  greater  dynamic  range , so  optimum results  are=
=20
obtained , when the  signal is  presented  to the  interface, as close to t=
o=20
the  original as  possible , the  DSP filter profiles are  tailored to the=
=20
mode/speed in use

This can be  noticed  with the  new  generation of   SDR  support software =
,=20
where  audio/voice recovery  can be  superior to conventional hardware=20
based systems

With hardware filtering , there  are  transit  (group) delays which  can=20
alter the  amplitude / time  , either  from  on/off  keying  or  with FSK,=
=20
this can  be  observed when  sending  wide  band  FSK , although  the  audi=
o=20
level  remains  constant and  'phase continuous'  , its possible  some time=
s=20
to  see a  'am modulation'  envelope  on the  carrier    ... $$$$   can=20
solve this  problem , but  for  most  Ham  kit its  something  that=20
'happens'

Physical  constraints , if  there  is  a  very large  carrier in the  pass=
=20
band  and  this  is pushing  the  hardware into  non-linearity / A/D  to=20
over  range  , giving   quantising  errors, then  , yes  filtering would=20
help , but  its more  likely  its the  analogue  path  that's  causing=20
intermod products .....reducing  the  rf/if gain will  provide the  solutio=
n

I think that's  about the  picture , if  Jim's  about , im sure  he  will=
=20
fill in the  gaps

73 -G..




--------------------------------------------------
From: "Mike Dennison" <mik=
e.dennison@ntlworld.com>
Sent: Wednesday, July 11, 2012 10:18 AM
To: <rsgb_lf_group@black=
sheep.org>; <r=
sgb_lf_group@yahoogroups.co.uk>
Subject: Re: LF:  OPERA  Question

>> Narrow   IF filters  are  not  desirable  and   reduce the
>> performance of the  demodulator  , better  simply  use  SSB  filte=
r
>> GL ..73 -G..
>
> Graham,
>
> Why is that the case? What does the considerable extra bandwidth
> achieve? Is the SSB bandwidth optimal, or would it be even better
> with 10kHz bandwidth, or 100kHz?. Why is 3kHz better than perhaps
> 1kHz or 2kHz?
>
> At first glance it appears crazy to let in all sorts of adjacent
> channel QRM (the bandwidth is more than ten times the size of the
> entire Opera window) when using a mode that occupies a fraction of
> 1Hz.
>
> Is it simply that the 1.7kHz Tx tone is high enough for the SSB
> filter to kill its harmonics, and on receive it is difficult to get a
> 1.7kHz tone out of a CW filter, even with passband shifting.
>
> Am I missing something?
>
> 73 de Mike, G3XDV
> g3xdv.blogspot.co.uk
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
>
>=20
----------MB_8CF2DB3D9A21311_2624_1F3A77_webmail-m156.sysops.aol.com--