DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
  s=s1024; d=btopenworld.com;
  h=DKIM-Signature:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:References:In-Reply-To:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE;
  b=vfzUJhPJfzG7xR308XbIttXVwz/GVF5urWoELLpCWeZScXoGFFWxBKyqZuVJDPkE/S7+25Hg2mDgva1bjjnz080gX/4PNLsSPaKvGfpqTPXh7SvtmZevNa00fqBY08HVZIAUbCfp7u//YcHG7jTK+QntQxZLhXFli/U+xcwJMkQ=  ;
Message-ID: <805AC05E834C4F7DA019C36A04013479@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4EF3689B.1030902@iup.uni-heidelberg.de>
In-Reply-To: <4EF3689B.1030902@iup.uni-heidelberg.de>
Date: Fri, 23 Dec 2011 11:17:12 -0000
MIME-Version: 1.0
DomainKey-Status: good (testing) 
Subject: LF: Re: Automatic Variometer adjustment at DK7FC
Content-Type: text/plain;
	format=flowed;
	charset="iso-8859-15";
	reply-type=response
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d003.1 ; domain : btopenworld.com DKIM : fail  
x-aol-sid: 3039ac1d40d84ef4636b4a3f
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Dear Stefan,

That is a nice simple circuit - I may well try something very similar at my 
QTH over the Christmas holiday, if time allows...

I suppose one advantage of a passive, "signal powered" phase detector for 
this scheme is that the phase detector output automatically becomes zero 
when the transmit signal is not present, which will prevent unwanted tuner 
operation on receive. As well as the BAT42 diodes providing a dead zone in 
servo operation close to the resonance point, I guess the inertia of the 
motor and gearbox will produce some hysteresis, moving the variometer to a 
very slightly over-adjusted position after the motor drive is removed, which 
will also help to prevent the system continuously searching around the 
correct tuning point. I expect one can optimise the resistor in series with 
the motor, as well as the amplifier gain, to get the best operation  of this 
feature.

Cheers, Jim Moritz
73 de M0BMU