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From: John Rabson <john.rabson@numeo.fr>
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Date: Thu, 22 Dec 2011 21:20:58 +0100
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To: rsgb_lf_group@blacksheep.org
Subject: Re: ***CECI EST UN SPAM*** Re: LF: Re: Automatic Variometer adjustment at DK7FC
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Mal,

The basic equations of rocketry can be put in the back of an envelope.  =
The engineering aspects are much more challenging.

John F5VLF

On 22 Dec 2011, at 19:47CET, mal hamilton wrote:

> Maybe you need one, you seem to have gone off Resonance!!!!!!!!!!!!!!!
> again. A variometer is hardly rocket science.
>=20
>=20
>=20
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> ----- Original Message -----
> From: "Roger Lapthorn" <rogerlapthorn@gmail.com>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Thursday, December 22, 2011 6:22 PM
> Subject: Re: LF: Re: Automatic Variometer adjustment at DK7FC
>=20
>=20
> Mal,
> Are you totally unable to say ANYTHING good, supportive or kind to =
anyone?
> Stefan 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.
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> Stefan,
> Excellent work - well done.
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> 73s
> Roger G3XBM
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> -- Via my iPod Touch 4g --
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> On 22 Dec 2011, at 18:08, "mal hamilton" <g3kevmal@talktalk.net> =
wrote:
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>> 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=E4fer" <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
>>=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 =
voltage
>>> 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
>>=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
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