References: <4EF3689B.1030902@iup.uni-heidelberg.de> <000d01ccc0d4$b01a5fe0$0401a8c0@xphd97xgq27nyf>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
In-Reply-To: <000d01ccc0d4$b01a5fe0$0401a8c0@xphd97xgq27nyf>
Message-Id: <8AB4FC73-8AD1-4DBA-B735-F4FEFC88F40D@gmail.com>
Date: Thu, 22 Dec 2011 18:22:29 +0000
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Mime-Version: 1.0 (1.0)
Subject: Re: LF: Re: Automatic Variometer adjustment at DK7FC
Content-Type: text/plain;
	charset=utf-8
Content-Transfer-Encoding: quoted-printable
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-m287.1 ; domain : gmail.com DKIM : pass  
x-aol-sid: 3039ac1d60ca4ef375a45061
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Mal,
Are you totally unable to say ANYTHING good, supportive or kind to anyone?  S=
tefan does not need, or deserve, your sarcasm or ill will and neither do the=
 rest of us. Please, have the good grace to acknowledge a piece of good work=
 or say nothing at all.=20

Stefan,
Excellent work - well done.=20

73s
Roger G3XBM

-- Via my iPod Touch 4g --

On 22 Dec 2011, at 18:08, "mal hamilton" <g3kevmal@talktalk.net> wrote:

> This is a terrific achievement and you are so excited, if you need one. In=

> my case I DO NOT
> G3KEV
>=20
> ----- Original Message -----
> From: "Stefan Sch=C3=A4fer" <Stefan.Schaefer@iup.uni-heidelberg.de>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Thursday, December 22, 2011 5:27 PM
> Subject: LF: Automatic Variometer adjustment at DK7FC
>=20
>=20
>> LF,
>>=20
>> I'm totally thrilled.
>> Yesterday in the night i designed a circuit to automatically resonate my
>> LF TX system by tuning the variometer. This allows to exactly hold the
>> phase and hold the antenna in resonance in changing sourrounding
>> conditions, like upcoming rain. But the most useful feature is: It
>> automatically adjusts the variometer if i do QSY (remote
>> operation!),e.g. if i go from 137.7 to 136.172 it re-adjusts the system
>> in less than 5 seconds!
>>=20
>> A small drive engine is used to turn the small coil into the main LF
>> loading coil, see:
>>=20
> http://dl.dropbox.com/u/19882028/LF/LF_variometer_drive_engine_arrangement=
.j
> pg
>> The drive engine works from 3...24V DC and takes 0.15A. It is steered
>> automatically by the circuit described below.
>>=20
>> The basic phase measurement circuit is taken from the M0BMU tuning meter
>> which one can find somewhere in the web and here:
>> http://dl.dropbox.com/u/19882028/LF/LFtunemeter.pdf BTW this tuning
>> meter is THE most useful device for antenna measurements at all, in my
>> opinion. The phase meter can directly drive an analog meter showing if
>> there is a positive or negative or no phase (=3Dresonance) between voltag=
e
>> and current. I took a very nostalgic and high quality analog meter to
>> nicely display the phase, see
>> http://dl.dropbox.com/u/19882028/LF/phase_meter.jpg. The circuit works
>> very nice and accurate. Resonance showing and the maximum of the antenna
>> current  exactly coincides. The circuit need no external power supply.
>>=20
>> The automatic motor drive circuit is here:
>>=20
> http://dl.dropbox.com/u/19882028/LF/DK7FC%20Automatic_variometer_tuner%20.=
jp
> g
>> It uses a quad OP amp, TL084. The first stage low pass filters and
>> amplifies the input voltage (taken from the analog phase meter, i.e.
>> switched in parallel), which has a DC part and a 137 kHz ripple. Another
>> OP amp generates the ground level which is in the middle of the 12
>> supply voltage (e.g. a battery or usual power supply). Then there are 2
>> comparators and a ICL7667 MOSFET driver. The 7667 works in a H bridge
>> configuration and inverse switches the outputs. The outputs can be
>> opposite in both directions, turning the engine CW or CCW or they can
>> have equal potential to stop the engine. 2  BAT42 shottky diodes are
>> used to generate a +- 0.3V threshold voltage to prevent self oscillation
>> arround the resonance point. The sensitivity of this circuit and the
>> phase threshold (hysterisis) can be aligned by adjusting the gain of the
>> input OP amp stage. The 7667 provides a low impedance output switching
>> and easy circuit design (no discrete push pull stages or so). A resistor
>> is put in series to the engine to reduce its speed a bit. Also a 0.1A
>> poly switch type fuse is put in series. This fuse is under-dimensioned
>> for the engine but will work for a few seconds before it interrupts.
>> This a some fail save protection in case the circuit may be damaged by
>> what ever and wants to turn the engine endless. Two anti parallel
>> switched LEDs indicate a running engine and its direction. They will be
>> labeled with L+ and L- later on the PA front panel.
>>=20
>> As a test i was transmitting a key down carrier at 137.7 kHz and
>> activated the circuit. A short impulse, indicated by one LED, set the
>> variometer EXACTLY to resonance. Then i QSYed to 137.0 kHz without
>> interrupting the TX. Since the frequency is lower, the L is to low. Thus
>> the circuit acts resistive-capacitive and the phase angle is negative. L
>> must be increased. The phase meter first jumped into the negative half
>> of the meter but it took about 2 seconds until it came quickly back to
>> zero where it stopped immediately.
>> I took the SpecLab frequency generator for that test (have an IQ mixer
>> that adds 125 kHz to the soundcard output, so i have to generate 12 kHz
>> to come out at 137 kHz). Then i added the FM modulator within the signal
>> generator and choosed a frequency deviation of 300 Hz and a period time
>> of 20 seconds. This is how that transmission looks on the DF6NM grabber:
>> http://dl.dropbox.com/u/19882028/LF/137kHz_%2B_FM0.3kHz.jpg
>> Without the automatic tuner beeing active the phase meter moves like a
>> windscreen wiper of course. When the circuit is active the needle of the
>> meter does very fine twitch but does not leave the resonance
>> significantly at all! :-)
>> The experts know how the LED blinking pattern must look: Faster blinking
>> on one side, then slower, then the other LED starts to blink slow, then
>> faster, slower again and so on :-))
>>=20
>> There are still no mechanical switches in series to the engine supply,
>> which would be another fail save circuit, to be added later, hopefully ;-=
)
>>=20
>> This may be one way for other LF transmitting stations to increase the
>> comfort of running their TX system by automatically adjusting their
>> system to resonance, even when QSYing by > 1 kHz :-)
>>=20
>> 73, Stefan/DK7FC
>>=20
>> PS: A photo of the board is here:
>> http://dl.dropbox.com/u/19882028/LF/automatic_variometer_board.jpg
>> PPS: Caution: This is not NEW and there are other circuits with similar
>> functionality existing!!!!!
>>=20
>>=20
>>=20
>=20
>=20