Return-Path: X-Spam-DCC: paranoid 1356; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_50_60,HTML_MESSAGE autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id t9VHQJfP012187 for ; Sat, 31 Oct 2015 18:26:19 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZsZsA-0005MO-Mn for rs_out_1@blacksheep.org; Sat, 31 Oct 2015 17:23:22 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZsZsA-0005ME-Bu for rsgb_lf_group@blacksheep.org; Sat, 31 Oct 2015 17:23:22 +0000 Received: from smtpout5.wanadoo.co.uk ([80.12.242.80] helo=smtpout.wanadoo.co.uk) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZsZr7-0002nn-Vh for rsgb_lf_group@blacksheep.org; Sat, 31 Oct 2015 17:23:21 +0000 Received: from AGB ([95.150.81.22]) by mwinf5d64 with ME id btMy1r00A0UtYh303tMyc2; Sat, 31 Oct 2015 18:22:01 +0100 X-ME-Helo: AGB X-ME-Date: Sat, 31 Oct 2015 18:22:01 +0100 X-ME-IP: 95.150.81.22 Message-ID: From: "Graham" To: References: <1981852865.20151017122027@chriswilson.tv><1530BFEB-9BC2-4CA2-A7A3-338629A98202@me.com><308511169.20151029202607@chriswilson.tv><56328B1F.2080901@posteo.de> In-Reply-To: Date: Sat, 31 Oct 2015 17:21:58 -0000 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-Scan-Signature: 86b6d14137f1f41166b7b27a17921f7a Subject: Re: LF: Automatic variometer circuit Content-Type: multipart/alternative; boundary="----=_NextPart_000_0034_01D11400.A5C34B50" 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 4732 This is a multi-part message in MIME format. ------=_NextPart_000_0034_01D11400.A5C34B50 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Its a Bi phase DC clamp , the amp has no gain as the inv is linked = to the o/p which is ground , the cap's probably provide a little = transcendental compliance =20 G, =20 From: Andy Talbot=20 Sent: Friday, October 30, 2015 7:20 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: Automatic variometer circuit Can I warn against one feature shown in the circuit diagram =20 The two 10uF electrolytics connected from the output of the first opamp = to the supply rails should not be there. They cause instability as = opamps are not designed to drive capacitive loads and frequently go = unstable. If an opamp is used to deliver a mid voltage rail like this, the = temptation to add extra decoupling should be avoided. The opamp output = gives a very low source impedance that will not benefit from any extra = decoupling. If you do not get nay instability using that circuit as it stands, then = you are very lucky - or perhaps it is oscillating and not noticed=20 I recently fell into this trap quite accidentally. It is so "natural" = to want to decouple supply rails with capacitors placed everywhere = that I placed several 100nF caps on a PCB without thinking. All of them = had to be removed to stabilise the resulting circuitry. Andy G4JNT On 29 October 2015 at 21:09, DK7FC wrote: Hi Chris, Am 29.10.2015 21:26, schrieb Chris Wilson: [...] albeit my loading coil needs manual tweaking to move to the right part of the band. Not sure of the = best way to remote tune it, it would be nice to have the ability to = move about the band without running outside in the dark. I may start = a thread about what alternatives there are, thanks again Erwin =20 I'm using a motor driven variometer which uses the phase meter circuit = of the M0BMU LF tuning meter. It is working well on LF, where my antenna = resonance is so sharp that i have to re-tune when doing QSY by 7 Hz. See: https://dl.dropboxusercontent.com/u/19882028/LF/LFtunemeter.pdf = https://dl.dropboxusercontent.com/u/19882028/LF/DK7FC%20Automatic_variome= ter_tuner%20.jpg = https://dl.dropboxusercontent.com/u/19882028/LF/automatic_variometer_boar= d.jpg = https://dl.dropboxusercontent.com/u/19882028/LF/LF_variometer_drive_engin= e_arrangement.jpg https://dl.dropboxusercontent.com/u/19882028/LF/phase_meter.jpg 2011 was a nice LF year for me!! :-) 73, Stefan ------=_NextPart_000_0034_01D11400.A5C34B50 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
Its a   Bi phase  DC clamp  , the  amp has = no gain=20 as the  inv is linked to the  o/p   which is  = ground ,=20 the  cap's probably  provide  a =20 little  transcendental   compliance 
 
G,
 
 

 
From: Andy Talbot
Sent: Friday, October 30, 2015 7:20 PM
To: rsgb_lf_group@blacksheep.org= =20
Subject: Re: LF: Automatic variometer = circuit

Can I warn against one feature shown in the circuit = diagram =20
The two 10uF electrolytics connected from the output of the first = opamp to=20 the supply rails should not be there.   They cause instability as = opamps=20 are not designed to drive capacitive loads and frequently go = unstable.

If an opamp is used to deliver a mid voltage rail like this, the = temptation=20 to add extra decoupling should be avoided.   The opamp output gives = a very=20 low source impedance  that will not benefit from any extra=20 decoupling.

If you do not get nay instability using that circuit as it stands, = then you=20 are very lucky  - or perhaps it is oscillating and not = noticed 

I recently fell into this trap quite accidentally.   It is so=20 "natural" to want to  decouple supply rails with capacitors placed=20 everywhere  that I placed several 100nF caps on a PCB without=20 thinking.  All of them had to be removed to stabilise the resulting = circuitry.

Andy  G4JNT


On 29 October 2015 at 21:09, DK7FC <selberdenken@posteo.de> wrote:
Hi Chris,

Am 29.10.2015 21:26, schrieb Chris=20 Wilson:
[...] albeit my loading coil needs=20 manual
tweaking  to  move to the right part of the = band. Not=20 sure of the best
way  to  remote  tune it, it = would be=20 nice to have the ability to move
about  the  band  = without  running  outside in the dark. I may start = a
thread=20 about what alternatives there are, thanks again Erwin
 =20  

I'm using a motor driven variometer which = uses the=20 phase meter circuit of the M0BMU LF tuning meter. It is working well = on LF,=20 where my antenna resonance is so sharp that i have to re-tune when = doing QSY=20 by 7 Hz.
See:
https://dl.dropboxusercontent.com/u/19882028/LF/LFtunemet= er.pdf
https://dl.dropboxusercontent.com/u/19882028/LF/DK7FC%20A= utomatic_variometer_tuner%20.jpg
https://dl.dropboxusercontent.com/u/19882028/LF/automatic= _variometer_board.jpg
https://dl.dropboxusercontent.com/u/19882028/LF/LF_variom= eter_drive_engine_arrangement.jpg
https://dl.dropboxusercontent.com/u/19882028/LF/phase_met= er.jpg

2011=20 was a nice LF year for me!! :-)

73,=20 Stefan



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