Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-da04.r1000.mx.aol.com (Internet Inbound) with ESMTP id B57133800009E; Wed, 11 Jul 2012 19:44:22 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Sp6Yu-0003nF-AB for rs_out_1@blacksheep.org; Thu, 12 Jul 2012 00:43:16 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Sp6Yt-0003n6-Kl for rsgb_lf_group@blacksheep.org; Thu, 12 Jul 2012 00:43:15 +0100 Received: from smtpout5.wanadoo.co.uk ([80.12.242.80] helo=smtpout.wanadoo.co.uk) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1Sp6Yq-00066q-Lw for rsgb_lf_group@blacksheep.org; Thu, 12 Jul 2012 00:43:14 +0100 Received: from AGB ([2.26.14.231]) by mwinf5d63 with ME id ZBjA1j0064z6akJ03BjAVX; Thu, 12 Jul 2012 01:43:11 +0200 Message-ID: <97A4971B4EDA4297832CD2C85C342CEB@AGB> From: "Graham" To: References: , <4FFC3518.1030405@xs4all.nl>, <4FFD5313.6103.333D978@mike.dennison.ntlworld.com> <1342044548.74534.YahooMailNeo@web171606.mail.ir2.yahoo.com> In-Reply-To: <1342044548.74534.YahooMailNeo@web171606.mail.ir2.yahoo.com> Date: Thu, 12 Jul 2012 00:43:10 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 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: Each to his own Pete, Really its only slowly that the amount of work and technical input that's needed to produce one of these numeric based data modes is becoming apparent , odd as you say some of the fire fights over mode V mode , cpu loading etc [...] 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 [80.12.242.80 listed in list.dnswl.org] 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 4bc17085406dca8cb02959d4b62a7d31 Subject: Re: LF: OPERA Question Content-Type: multipart/alternative; boundary="----=_NextPart_000_010D_01CD5FC7.4FE809F0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=CASHCASHCASH,HTML_30_40, HTML_MESSAGE,MISSING_OUTLOOK_NAME 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: 0:2:492901728:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d404c4ffe0fd67ed5 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_010D_01CD5FC7.4FE809F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Each to his own Pete, Really its only slowly that the amount of work and technical = input that's needed to produce one of these numeric based data = modes is becoming apparent , odd as you say some of the fire fights = over mode V mode , cpu loading etc =20 A simple question over filter bandwidth reveals yet another = layer of maths and intrigue, based round the definition of the = word 'filter' weather you are referring to a analogue device or a = computational routine that's deployed to provide a best fit of = the recovered 'pulse' ... reminds me of a episode of the Avengers = , every time you open a door the room has changed , in this case = the words have different meanings . . . same thing with the spread = spectrum knees up , spreading routines applied to data , nothing = to do with radio bandwidth ..=20 In simplicity , the answer from Jose was 'Do nothing to the signal = , leave all filtering to the software' selecting a narrow = filter adds phase shift , time delay and additional noise ....... = so direct conversion SDR is the optimum Rx system ! The main thing is 'we' have some pretty robust data modes to = play with on here , activity is increasing by the day and its = only July ! =20 73 - G ..=20 From: M0FMT=20 Sent: Wednesday, July 11, 2012 11:09 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: OPERA Question Hi Graham SDR; doing your best to drag them kicking and screaming into the future. = I don't get the resistance..... the QEX (ARRL) files are available to = all (unlike other national outfits) on DSP, a technology which has been = with us for a decade or two! But easier to implement these days. 73 es GL Pete M0FMT IO91UX From: Graham To: rsgb_lf_group@blacksheep.org=20 Cc: james.moritz@btopenworld.com=20 Sent: Wednesday, 11 July 2012, 16:51 Subject: 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 in a limited bandwidth , ringing due to the Q , similar to CW = , narrow filters tend to round the CW signal The DSP engine is better equipped to differentiate between = carrier and noise and has a much greater dynamic range , so = optimum results are obtained , when the signal is presented to the = interface, as close to to the original as possible , the DSP filter = profiles are tailored to the mode/speed in use This can be noticed with the new generation of SDR support = software , where audio/voice recovery can be superior to conventional = hardware based systems With hardware filtering , there are transit (group) delays which = can alter the amplitude / time , either from on/off keying or = with FSK, this can be observed when sending wide band FSK , = although the audio level remains constant and 'phase continuous' , = its possible some times to see a 'am modulation' envelope on the = carrier ... $$$$ can solve this problem , but for most Ham kit = its something that 'happens' Physical constraints , if there is a very large carrier in the = pass band and this is pushing the hardware into non-linearity / = A/D to over range , giving quantising errors, then , yes = filtering would help , but its more likely its the analogue path = that's causing intermod 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 fill in the gaps 73 -G.. -------------------------------------------------- From: "Mike Dennison" Sent: Wednesday, July 11, 2012 10:18 AM To: ; Subject: 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.. >=20 > Graham, >=20 > 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? >=20 > 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. >=20 > 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. >=20 > Am I missing something? >=20 > 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 >=20 >=20 ------=_NextPart_000_010D_01CD5FC7.4FE809F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Each to  his  own Pete,
 
Really  its  only  slowly that  the  = amount=20 of  work and  technical  input that's =20 needed  to  produce  one of these numeric =20 based  data  modes is  becoming  apparent , = odd =20 as you  say some of the  fire fights  over  mode V = mode ,=20 cpu loading  etc 
 
A simple  question  over  filter  bandwidth=20 reveals   yet  another  layer of  maths  = and =20 intrigue, based round  the  definition =20 of  the  word 'filter'  weather  you are =20 referring to a  analogue  device  or=20 a  computational  routine  that's  = deployed =20 to  provide a  best  fit  of the  = recovered =20 'pulse' ... reminds  me  of  a episode of the =20 Avengers  , every time  you open a  door  the =20 room  has changed  , in this  case the  words =20 have  different  meanings . . . same thing  with = the  spread=20 spectrum knees  up ,  spreading  routines  = applied =20 to  data  , nothing  to  do  with  = radio =20 bandwidth ..
 
In simplicity , the  answer from Jose  was  = 'Do =20 nothing  to the  signal , leave  all  = filtering  to the=20 software'    selecting  a  narrow  = filter =20 adds   phase shift , time delay  and  = additional  noise=20 ....... so  direct  conversion  SDR  is the =20 optimum  Rx  system !
 
The  main  thing  is  'we'  have  = some =20 pretty robust  data  modes to  play  with  on=20 here  , activity is  increasing  by the  day  = and =20 its  only   July  !  
 
73 - G ..
 

From: M0FMT
Sent: Wednesday, July 11, 2012 11:09 PM
To: rsgb_lf_group@blacksheep.org= =20
Subject: Re: LF: OPERA Question

Hi Graham
 
SDR; doing your best to drag them kicking and screaming into the = future. I=20 don't get the resistance..... the QEX (ARRL) files are available to all = (unlike other national outfits) on DSP, a = technology=20 which has been with us for a decade or two! But easier to implement = these=20 days.
73 es GL Pete M0FMT IO91UX
From: Graham <g8fzk@g8fzk.fsnet.co.uk>To: rsgb_lf_group@blacksheep.org= =20
Cc:=20 james.moritz@btopenworld.com
Sent: Wednesday, 11 July 2012,=20 16:51
Subject: Re: = LF: OPERA=20 Question

''At first glance it appears=20 crazy''

Mike,

Welcome to the crazy world of  = JR =20 !

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

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

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

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

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

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

73=20 = -G..




-------------------------------------------------= -
From:=20 "Mike Dennison" <mike.dennison@ntlworld.com<= /A>>
Sent:=20 Wednesday, July 11, 2012 10:18 AM
To: <rsgb_lf_group@blacksheep.= org>;=20 <rsgb_lf_group@yahoogro= ups.co.uk>
Subject:=20 Re: LF:  OPERA  Question

>> Narrow  IF=20 filters  are  not  desirable  and  reduce=20 the
>> performance of the  demodulator  , = better =20 simply  use  SSB  filter
>> GL ..73 = -G..
>=20
> Graham,
>
> Why is that the case? What does the=20 considerable extra bandwidth
> achieve? Is the SSB bandwidth = optimal, or=20 would it be even better
> with 10kHz bandwidth, or 100kHz?. Why = is 3kHz=20 better than perhaps
> 1kHz or 2kHz?
>
> At first = glance it=20 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)=20 when using a mode that occupies a fraction of
> 1Hz.
> =
> Is=20 it simply that the 1.7kHz Tx tone is high enough for the SSB
> = filter to=20 kill its harmonics, and on receive it is difficult to get a
> = 1.7kHz=20 tone out of a CW filter, even with passband shifting.
>
> = Am I=20 missing something?
>
> 73 de Mike, G3XDV
>=20 g3xdv.blogspot.co.uk
> = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
> =
>=20



------=_NextPart_000_010D_01CD5FC7.4FE809F0--