Thomas, Will this one work in the 20Hz and lower Pc1 -4, till milliHz range ? Edward ... [Non-text portions of this message have been removed]...
16362
Thomas D. Dean
tomdean@...
Oct 20, 2010 4:59 pm
... Look at the schematic in files/Tomdean. The preamp is DC to the output capacitors, large such that Xc <<50 at 1kHz. If the output capacitors are not loaded...
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Thomas D. Dean
tomdean@...
Oct 20, 2010 5:02 pm
On Wed, 2010-10-20 at 15:49 +0000, Edward van Ulft wrote: The bare board costs $12.00 each plus $15.00 one time setup. The two boards I made available, spoken...
16364
Edward van Ulft
snake1nl
Oct 21, 2010 12:57 am
Thomas, I miss decoupling caps in your design,yet maybe its better when you walk me through your design, especially that stash of caps I understand they are...
16365
Thomas D. Dean
tomdean@...
Oct 21, 2010 1:33 am
... C1,C2,C4,C5 are power supply filters. C3 is a space reserved for modification of IC1 gain. C6,C7,C8,C9 are dc isolation/coupling capacitors. If you look at...
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Richard B Georgina
wd4rbx...
Oct 21, 2010 4:41 am
Count me in for one or two. Rich ... But, before we get to that level, I have to load and characterize one... tomdean<< [Non-text portions of this message have...
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Edward van Ulft
snake1nl
Oct 21, 2010 9:04 pm
... Onderwerp: Re: VLF Preamp PCB Datum: Thu, 21 Oct 2010 20:56:17 +0000 Van: Edward van Ulft <vanulft@...> Aan: tomdean@... OK Thomas, ...
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Renato Romero
reromeroit
Oct 21, 2010 9:41 pm
Hello Alan, Unfortunately, the ISDN line is propriety of external service. I can not disconnect the wire from NT1 terminal. Bye, Renato ... [Non-text portions...
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Alan Melia
g3nyk
Oct 21, 2010 10:19 pm
Hi Renato, Ah in that case you need a squad of tame well trained termites ... Best Wishes Alan ... From: "Renato Romero" <ik1qfk@...> To:...
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Thomas D. Dean
tomdean@...
Oct 22, 2010 10:20 pm
Two things. 1. I posted the wrong schematic. I will post the correct one now. 2. The board is unstable when connected to a loop antenna, rapidly drifting to...
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Thomas D. Dean
tomdean@...
Oct 23, 2010 3:00 am
In recent conversations, having a very low amplifier input impedance was was preferred, to match the loop impedance. I have attempted to build several low...
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Paul
paul@...
Oct 23, 2010 7:40 am
... Yes, that's true. ... Not if you're designing for best signal/noise ratio. You must design the loop, or transform its impedance, so that it presents the...
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Walter
karula4711
Oct 23, 2010 2:13 pm
Hi group, JFET OpAmp, fast: 50 V/us GBP 20 MHz but delisted and no longer available. May I ask for a recommendation which is available in Germany (in small...
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Costas K
g7ahn
Oct 23, 2010 2:37 pm
... This IC is still available on eBay for US$ 3.99, see item #300360784307. Regards, Costas SV1XV...
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Thomas D. Dean
tomdean@...
Oct 24, 2010 4:23 am
I am trying to stay DC through the preamp. This means no transformer or coupling capacitors. The magnitude of impedance of my loop is 2.8 ohms at DC up to...
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mike l dormann
w7dra
Oct 24, 2010 5:30 am
why this wide band preamp? looking for natural radio signals? what is ev's air core loop antennas bandwidth? the one ohm one millihenry designs mike w7dra On...
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wolf_dl4yhf
dl4yhf
Oct 24, 2010 9:44 am
... just a quick reminder, they'll start transmitting on 17.2 kHz soon.. http://www.alexander.n.se/ 73, Wolf DL4YHF ....
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dl4yhf
Oct 24, 2010 10:49 am
Now tuning up, good copy in northwestern DL, but they still seem to adjust the alternator's speed .. 73, Wolf ....
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Thomas D. Dean
tomdean@...
Oct 25, 2010 12:29 am
I am reading the paper by Marco Bruno, http://www.vlf.it/looptheo7/looptheo7.htm I am looking at the AD797 Op Amp. The device is spec'd for a 50ma output...
... Paul, What did you use to model the antenna and amp? I tried some with the spice noise simulation, but, could not get anything near what you posted. I...
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Thomas D. Dean
tomdean@...
Oct 28, 2010 12:12 am
I used a signal generator, a 10k resistor and a scope to characterize my loop. I connected the signal generator to the loop, through the 10k resistor and...
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Paul
paul@...
Oct 28, 2010 7:22 am
... I used ngspice. I don't think it has any noise calculation built-in, so I modeled the noise for each significant source, then combined the results....
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renato
reromeroit
Oct 28, 2010 8:06 am
All reasonable. The AD797 was choosen for low noise, but of course it needs a buffer stage to drive a low-Z load. But I don't think that this may cause...
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Thomas D. Dean
tomdean@...
Oct 29, 2010 5:01 am
On Thu, 2010-10-28 at 07:08 +0000, Paul wrote: The latest version of ngspice, configured with ./configure --enable-xspice --enable-numparam --enable-x \ ...
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Paul
paul@...
Oct 29, 2010 6:56 am
... Thanks very much for the tip, I'll install that and try it out. Will save a lot of effort if it works. ... I don't have a Yahoo account so I can't look at...
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Paul
paul@...
Oct 30, 2010 3:11 pm
... I installed the latest ngspice and ran the loop/amp model that you sent. I cant understand or make sense of inoise_spectrum but the onoise_spectrum output...
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Thomas D. Dean
tomdean@...
Oct 30, 2010 6:58 pm
On Linux or any *nix system, I use octave and gnuplot with ngspice. I am using octave 3.2.4 and gnuplot 4.4 to do the ngspice analysis. I have an adaptation...
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Paul
paul@...
Oct 30, 2010 7:29 pm
That should do the trick Tom. You should get a nice broad peak on the abs(mac)./sqrt(monoise) plot. Can you send me a plot image? Yes I use a lot of awk and...
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Thomas D. Dean
tomdean@...
Nov 1, 2010 5:25 am
I am thinking of constructing a loop on a cube. I want the loop to be portable, so, the size is limited. My plan: Make a frame, with 3/4 inch pvc pipe. Glue...
