Return-Path: Received: from mtain-dd06.r1000.mx.aol.com (mtain-dd06.r1000.mx.aol.com [172.29.64.146]) by air-de01.mail.aol.com (v129.10) with ESMTP id MAILINDE014-5ea54dbc29d343; Sat, 30 Apr 2011 11:25:07 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dd06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 77A0438000150; Sat, 30 Apr 2011 11:25:03 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QGC1o-0003Kk-Nt for rs_out_1@blacksheep.org; Sat, 30 Apr 2011 16:24:16 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QGC1o-0003Kb-9Z for rsgb_lf_group@blacksheep.org; Sat, 30 Apr 2011 16:24:16 +0100 Received: from imr-da05.mx.aol.com ([205.188.105.147]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QGC1m-0006aq-DF for rsgb_lf_group@blacksheep.org; Sat, 30 Apr 2011 16:24:16 +0100 Received: from mtaout-db03.r1000.mx.aol.com (mtaout-db03.r1000.mx.aol.com [172.29.51.195]) by imr-da05.mx.aol.com (8.14.1/8.14.1) with ESMTP id p3UFO8MK007174 for ; Sat, 30 Apr 2011 11:24:08 -0400 Received: from White (nrbg-4d0746cd.pool.mediaWays.net [77.7.70.205]) by mtaout-db03.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 4AF1DE000090 for ; Sat, 30 Apr 2011 11:24:04 -0400 (EDT) Message-ID: From: "Markus Vester" To: References: <1304160593.1549.4.camel@gerhard-desktop> Date: Sat, 30 Apr 2011 17:24:02 +0200 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Re: CW beacon "BRK" on 137.00khz ??????? Content-Type: multipart/alternative; boundary="----=_NextPart_000_000F_01CC075B.661E6C70" 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=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-sid: 3039ac1d40924dbc29cf6998 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_000F_01CC075B.661E6C70 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Hi Gerhard, Jim, so this would look like a case of 3x LO harmonic mixing? This is actua= lly one of the fundamental drawbacks of a direct converting receiver.= For good dynamic range, you want to drive the mixer hard by a squarew= ave, but that introduces unwanted sensitivity around all odd LO harmon= ics. So for a wideband tunable receiver, you would require a set of sw= itched octave filters.=20 I own a preselector-less "FiFi-SDR" IQ-receiver, which is also sufferi= ng heavily from that effect, especially at LF due to mediumwave broadc= ast stations. Instead of adding the filter bank, I am actually conside= ring to convert it to a high-IF superhet with another mixer in the fro= ntend. Best 73, Markus (DF6NM) From: James Moritz=20 Sent: Saturday, April 30, 2011 1:16 PM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: Re: CW beacon "BRK" on 137.00khz ??????? Dear Gerhard, LF Group, There is an NDB "BRK" listed near Vienna on 408kHz, which is 3 x 136k= Hz.=20 Allowing for +/- a little frequency for the AM sidebands this could be= what=20 you are hearing - the active whip would pick this up, but a tuned TX= antenna=20 would attenuate it considerably. Perhaps a bit more preselection requi= red? Cheers, Jim Moritz 73 de M0BMU ----- Original Message -----=20 From: "Gerhard Hickl" > I'm working on a new DC-CW receiver and while testing, I found a > CW-Signal on 137.00 sending "BRK" every 10 seconds. >=20 ------=_NextPart_000_000F_01CC075B.661E6C70 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
Hi Gerhard, Jim,
 
so this would look like a case of 3x= LO harmonic=20 mixing? This is actually one of the fundamental drawbacks of a di= rect=20 converting receiver. For good dynamic range, you want to drive the mix= er hard by=20 a squarewave, but that introduces unwanted sensitivity around all= odd LO=20 harmonics. So for a wideband tunable receiver, you would require a set= of=20 switched octave filters.
 
I own a preselector-less "FiFi-S= DR"=20 IQ-receiver, which is also suffering heavily from that effect, especia= lly at LF=20 due to mediumwave broadcast stations. Instead of adding the= filter=20 bank, I am actually considering to convert it to a high= -IF=20 superhet with another mixer in the frontend.
 
Best 73,
Markus (DF6NM)

Sent: Saturday, April 30, 2011 1:16 PM
Subject: LF: Re: CW beacon "BRK" on 137.00khz=20 ???????
=
Dear Gerhard, LF Group,

There is an NDB "BRK"= =20 listed  near Vienna on 408kHz, which is 3 x 136kHz.
Allowing= for +/- a=20 little frequency for the AM sidebands this could be what
you are= hearing -=20 the active whip would pick this up, but a tuned TX antenna
would= attenuate=20 it considerably. Perhaps a bit more preselection required?

Chee= rs, Jim=20 Moritz
73 de M0BMU

----- Original Message -----
From: "G= erhard=20 Hickl" <gerhard.hickl@aon= .at>
> I'm=20 working on a new DC-CW receiver and while testing, I found a
>= CW-Signal=20 on 137.00 sending "BRK" every 10 seconds.
>


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