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(john.rabson@numeo.fr@217.67.155.178) by smtp.qtxt.dns-iol.com with SMTP; 22 Dec 2011 21:38:59 +0100 Mime-Version: 1.0 (Apple Message framework v1251.1) From: John Rabson X-Priority: 3 In-Reply-To: Date: Thu, 22 Dec 2011 21:39:04 +0100 Message-Id: References: <4EF3689B.1030902@iup.uni-heidelberg.de> <000d01ccc0d4$b01a5fe0$0401a8c0@xphd97xgq27nyf> <8AB4FC73-8AD1-4DBA-B735-F4FEFC88F40D@gmail.com> <003b01ccc0da$1f16c050$0401a8c0@xphd97xgq27nyf> To: rsgb_lf_group@blacksheep.org X-Mailer: Apple Mail (2.1251.1) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: Re: Automatic Variometer adjustment at DK7FC Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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 x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:449158496:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d60174ef395a0559f X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none OOPS! I meant _on_ the back of an envelope. John On 22 Dec 2011, at 21:20CET, John Rabson wrote: > Mal, >=20 > The basic equations of rocketry can be put in the back of an envelope. = The engineering aspects are much more challenging. >=20 > John F5VLF >=20 > On 22 Dec 2011, at 19:47CET, mal hamilton wrote: >=20 >> Maybe you need one, you seem to have gone off = Resonance!!!!!!!!!!!!!!! >> again. A variometer is hardly rocket science. >>=20 >>=20 >>=20 >>=20 >> ----- Original Message ----- >> From: "Roger Lapthorn" >> To: >> 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. >>=20 >> Stefan, >> Excellent work - well done. >>=20 >> 73s >> Roger G3XBM >>=20 >> -- Via my iPod Touch 4g -- >>=20 >> On 22 Dec 2011, at 18:08, "mal hamilton" = wrote: >>=20 >>> 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" >>> To: >>> 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 >>>=20 >>>=20 >>=20 >>=20 >>=20 >>=20 >=20 >=20 >=20