Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w0QFMRIl008470 for ; Fri, 26 Jan 2018 16:22:30 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ef5kj-0003fv-5K for rs_out_1@blacksheep.org; Fri, 26 Jan 2018 15:17:17 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ef5ki-0003fm-M0 for rsgb_lf_group@blacksheep.org; Fri, 26 Jan 2018 15:17:16 +0000 Received: from mail-wm0-x234.google.com ([2a00:1450:400c:c09::234]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ef5kd-0007QZ-7q for rsgb_lf_group@blacksheep.org; Fri, 26 Jan 2018 15:17:15 +0000 Received: by mail-wm0-x234.google.com with SMTP id 141so21762574wme.3 for ; Fri, 26 Jan 2018 07:17:10 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=JJbP+wsRQnwQvEj2OvobYQoOaNommmLCMXlGKqKJR2E=; b=FUHukZwG+FGXdiiiFna3dMht92plJWrvxfSERyb+abIYKtOCEw03MzMb1VMQxWftRw 4/wvD7RHyvCsjs23wwKfC1iN4sr+QT4diF8sFU9z8wBymyfSonnXJrUpQcWp3eqnF3nf bu+LVAhB1ImiC0FeHhSBqEUb39MvZp00C2UoIj5RMKzyd7OjuZFPS1R/JIl4GL/RF19r wUEPlOAuuBz0J+nRwXecNFgCrTK/aMlm49pG0T24qWkyoSDdYRmsrlNhCHaQCYB/TOjN IYZbniYUNkbSaFFgta9CZ7lDqoGOv5EH1aTCLlF0+cXLND/PkH1bBzQQmcMLnvhk47/s mQVA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=JJbP+wsRQnwQvEj2OvobYQoOaNommmLCMXlGKqKJR2E=; b=eo8UfRrNFjuK4R0QKwn0Bx6UuoGTwfGGgqtTEG9mSTC5d5amifb1k22xy25e9QxJPA Q+JEv2HTxdt9toJEuWpnHTFJOt6LaIhnZtqDztaYj8Ef0lxrFKPdP7aUx5gzMkFPepUi NIU01FvZ8p1Ss8+zPL47kBMHq5/ljw48Gso7JZGg753fskMx10n5r2nF9dN+mDAlRI7h uebdabrNgA0OM2rVE/Cdehh62ZfMd/Twcx7ZSv5osGvW8KrSFhbxWt9CZEPr7MfTQu8h Ldm5fAv+ycBv+YUqTC4Qyp4UqVIwjkg/hnr9IUeHy0K3e5YOnyC7/cczX7vk49lOSxOW +1OQ== X-Gm-Message-State: AKwxyteZ0QR3PbgWjryfxJy9nFVl/0NqkmCmfrTpaaCDZitfKwXS2Izg 31TQAGkCzJt7LMNmjtDrWiQ3cD3Q2rkZ7/oqoio= X-Google-Smtp-Source: AH8x2258RbsBkuCaxJoNbIhmohazHL5ip6m9HkZtXx0XgpPjWMyjcS0xT+ppPoaPMgu+xIoRCyzoIccZxbrEAV2mkww= X-Received: by 10.80.177.13 with SMTP id k13mr34067818edd.154.1516979830225; Fri, 26 Jan 2018 07:17:10 -0800 (PST) MIME-Version: 1.0 Received: by 10.80.179.198 with HTTP; Fri, 26 Jan 2018 07:17:09 -0800 (PST) In-Reply-To: References: <1371247928.20180126134524@gmail.com> From: Andy Talbot Date: Fri, 26 Jan 2018 15:17:09 +0000 Message-ID: To: LineOne X-Spam-Score: 1.0 (+) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: The linearly biassed gates used to buffer the input of the Softrock LO fail at low frequencies, breaking up into spurious oscillations at the threshold changeover, not operating the divider properly and hence giving an apparent change in freq I had this problem when I was using a "Finningley Dongle" driven by an external DDS source. The solution was to add my own Schmitt trigger input buffer before letting it get to the 74HC74 device. That way it would work down to below 10kHz RF input. [...] Content analysis details: (1.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andy.g4jnt[at]gmail.com) 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid 1.0 FREEMAIL_REPLY From and body contain different freemails X-Scan-Signature: e43fe7093e9b3ae0dc118eec4efba8a5 Subject: Re: LF: Softrock RX divider IC problem, unexpected frequency out Content-Type: multipart/alternative; boundary="f403045c3d6ae9929a0563af63fb" 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=HTML_FONTCOLOR_UNSAFE, 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 --f403045c3d6ae9929a0563af63fb Content-Type: text/plain; charset="UTF-8" The linearly biassed gates used to buffer the input of the Softrock LO fail at low frequencies, breaking up into spurious oscillations at the threshold changeover, not operating the divider properly and hence giving an apparent change in freq I had this problem when I was using a "Finningley Dongle" driven by an external DDS source. The solution was to add my own Schmitt trigger input buffer before letting it get to the 74HC74 device. That way it would work down to below 10kHz RF input. Andy G4JNT On 26 January 2018 at 15:06, David Bowman wrote: > Hi Chris. > It may be worth going back to the oscillator and making sure the frequency > there is what you expect. > Could be that the divider is working fine, but the input to it is shifting > around. > > 73 > > David G0MRF > > On Fri, Jan 26, 2018 at 1:45 PM, Chris Wilson wrote: > >> >> >> Hello LF and VLF folk! >> >> I have built a couple of Softrock Lite II IF frequency receivers, >> normally they would be used to view another receiver's IF on a >> bandscope, but popularly they are also used on low and medium >> frequencies as stand alone SDR receivers. The MF one works fine. Th LF >> one was intermittent, then failed with high current draw. I isolated >> it to a faulty or shorted divider chip. The original one was marked >> 78C49NM. I couldn't find one of those, so plumped for one from RS >> Components here in the UK, a CD74AC74M96G4, RS part number 662-6939 >> The oscillator worked on the bench and from an xtal frequency of 461.5 >> kHz gave the expected divide by 4 output of 115.364 or very close. >> Then suddenly it started receiving broadcast stations and the divided >> outputs Q and /Q were on 153.814 KHz! There they remain. Fiddling I >> briefly saw a return to 115.36 Khz, but it was not for long. All >> voltages to it's pins are correct at 5V. I am not sure if it's a >> faulty divider, or a bad connection or short. >> >> Xtal case is grounded and seems stable. R16 in the oscillator changed >> on advice from 22.1k to 10k as they apparently tend to stop running >> with 21.1k there. I attach the schematic. Wrong IC? Details of the >> divider's operation are at http://www.wb5rvz.org/softrock_lite_ii/03_div >> >> The new IC details are at https://uk.rs-online.com/web/p >> /flip-flop-ics/6626939/ >> >> I see these frequencies on these pins: >> >> Pin 3 : 464.444 kHz >> >> Pin 11 : 464.444 >> >> Pin 12 : 153.814 >> >> Pin 8 : 153.814 >> >> Pin 2 : 307.625 >> >> Pin 2 : 307.625 >> >> Is this a random IC fault or does it have some mathematical >> correlation? My maths is pitiful! >> >> Not sure what to do now, I have another IC but before risking pad >> damage thought it prudent to ask, many thanks. >> >> Pins 14 and 2 on the mixer IC show good, 90 degree out of phase square >> waveforms of normal amplitude on a scope, but at 153.814 KHz.... >> >> Schematic is at http://www.gatesgarth.com/schematic.jpg >> >> >> >> -- >> Best regards, >> Chris mailto:dead.fets@gmail.com >> >> >> > --f403045c3d6ae9929a0563af63fb Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
The linearly biassed gates used to buffer the input of the= Softrock LO fail at low frequencies, breaking up into spurious oscillation= s at the threshold changeover, not operating the divider properly=C2=A0 and= hence giving an apparent change in freq=C2=A0 I had this problem=C2=A0 whe= n I was using a "Finningley Dongle" driven by an external DDS sou= rce.=C2=A0 =C2=A0The solution was to add my own Schmitt trigger input buffe= r before letting it get to the 74HC74 device.=C2=A0 =C2=A0That way=C2=A0 it= would work down to below 10kHz RF input.

Andy=C2=A0 G4J= NT

On = 26 January 2018 at 15:06, David Bowman <davidg0mrf@gmail.com> wrote:
Hi Chris.
It may be worth going back to the oscillator and maki= ng sure the frequency there is what you expect.
Could be that the = divider is working fine, but the input to it is shifting around.

73<= br>
David=C2=A0 G0MRF

On Fri, Jan 26, 2018 at 1:45 PM, Chris Wilson <de= ad.fets@gmail.com> wrote:
<= br>
Hello=C2=A0 LF and VLF folk!

I have built a couple of Softrock Lite II IF frequency receivers,
normally they would be used to view another receiver's IF on a
bandscope, but popularly they are also used on low and medium
frequencies as stand alone SDR receivers. The MF one works fine. Th LF
one was intermittent, then failed with high current draw. I isolated
it to a faulty or shorted divider chip. The original one was marked
78C49NM. I couldn't find one of those, so plumped for one from RS
Components here in the UK, a CD74AC74M96G4, RS part number 662-6939
The oscillator worked on the bench and from an xtal frequency of 461.5
kHz gave the expected divide by 4 output of 115.364 or very close.
Then suddenly it started receiving broadcast stations and the divided
outputs Q and /Q were on 153.814 KHz! There they remain. Fiddling I
briefly saw a return to 115.36 Khz, but it was not for long. All
voltages to it's pins are correct at 5V. I am not sure if it's a faulty divider, or a bad connection or short.

Xtal case is grounded and seems stable. R16 in the oscillator changed
on advice from 22.1k to 10k as they apparently tend to stop running
with 21.1k there. I attach the schematic. Wrong IC? Details of the
divider's operation are at http://www.wb5rvz.org/so= ftrock_lite_ii/03_div

The new IC details are at https://uk.rs-online.= com/web/p/flip-flop-ics/6626939/

I see these frequencies on these pins:

Pin 3 : 464.444 kHz

Pin 11 : 464.444

Pin 12 : 153.814

Pin 8 : 153.814

Pin 2 : 307.625

Pin 2 : 307.625

Is this a random IC fault or does it have some mathematical
correlation? My maths is pitiful!

Not sure what to do now, I have another IC but before risking pad
damage thought it prudent to ask, many thanks.

Pins 14 and 2 on the mixer IC show good, 90 degree out of phase square
waveforms of normal amplitude on a scope, but at 153.814 KHz....

Schematic is at http://www.gatesgarth.com/schematic.jpg<= /a>



--
Best regards,
=C2=A0Chris=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 mailto:dead.fets@gmail.com




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