Re: Beginner's Question re LT Spice and RF Filter Design
Andy,
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Thank you. I was to have uploaded the .asc file into temp per the group protocol but your answer will suffice. Appreciate the advisory and support.
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William, k6whp
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"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: Beginner's Question re LT Spice and RF Filter Design
I uploaded your schematic file.? It is "RF_Filter_Chebyshev.asc" and it is currently in the Temp folder, in the group's Files section. ?
Andy
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Re: Beginner's Question re LT Spice and RF Filter Design
Andy,
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I did so instinctively and THEN read the group webpage. My apologies for the oversight.
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--
William, k6whp
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"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: Beginner's Question re LT Spice and RF Filter Design
On Sat, Mar 29, 2025 at 08:48 PM, k6whp wrote:
I note that the display shows this model to initially be -6dB and wonder why.
It's a pretty simple reason, which looks obvious after you realize it.
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Your signal source has a 1 (volt) amplitude and 50 ohm source impedance.? It is a Thevenin source, so you've got 1 volt behind the 50 ohm source resistance.? When that is terminated (into a 50 ohm load), it is a voltage divider that cuts the voltage in half, so that the terminal voltage across V1 is 0.5 volt, resulting in a nominal 6 dB loss.
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When using AC sources like this, set their amplitude to 2 (volts), so that they make 1 (volt) when terminated.
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Andy
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Re: Beginner's Question re LT Spice and RF Filter Design
On Sat, Mar 29, 2025 at 08:48 PM, k6whp wrote:
Am designing a low pass filter for the 20m amateur band, code below. (My apologies if this violates group protocol. Advise and I will adhere in the future.)?
Even better:? Why not read the group's guidelines on the main group webpage.
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You attempted to paste your schematic file into the message.? Never paste or attach any files into a group message.
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Andy
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Beginner's Question re LT Spice and RF Filter Design
Am designing a low pass filter for the 20m amateur band, code below. (My apologies if this violates group protocol. Advise and I will adhere in the future.)?
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I note that the display shows this model to initially be -6dB and wonder why. Again, truly a beginner. Links to appropriate material gratefully received.
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Thank you in advance.
--
William, k6whp
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"Cheer up, things could get worse. So I cheered up and things got worse."
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Re: Simulating Using PyLTSpice Takes Too Long
Simply use six instances of your circuit on single page and modify connection\termination for each individual circuits.
Yes, it`s not elegant, but works as simple as hammer.
Not sure if some kind of "stepping" will work faster.
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Kind regards,
Victor
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Re: Simulating Using PyLTSpice Takes Too Long
On Sat, Mar 29, 2025 at 06:27 PM, <davitkharshiladze26@...> wrote:
I have made contact with PyLTspice developer, and he pointed out that It could not be sped up further.
I consider that an odd thing to say.
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On the one hand, it suggests that his program adds pre-programmed delays which can't be reduced further, without risk of failure.
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On the other hand, it suggests that he knows your circuit, and he's telling you it can't simulate faster.? How would be know that?? I think you were saying that the simulation itself (with just LTspice) is about 1 second (each time) and that 1 second is too slow.
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Andy
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Re: PTC model with internal temperature rise
On Sat, Mar 29, 2025 at 06:13 PM, <pilou@...> wrote:
It's OK now, I just uploaded it.
Filename is "ptc_sh.zip".
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It is currently in the Temp folder at the group's website. ?
Andy
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Re: Simulating Using PyLTSpice Takes Too Long
On Sat, Mar 29, 2025 at 06:19 PM, <davitkharshiladze26@...> wrote:
1 second is too much for my purposes, and runtime is 1 second whether I use LTspice or PyLTspice? to run the simulaiton
Is 1 second what LTspice reports in its .log file?? Or is that from looking at a clock on the wall, from start to finish?
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If it really takes 1 second to run a simulation, then perhaps that is what it needs, period.? You implied that your actual circuit is "large", so maybe it really needs that much time to converge on the operating point, and that's where most of the time goes.? It is possible that you can reduce the convergence time.
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It might also help to know what version of LTspice you are using.? It has gone through some rather significant changes in the last couple of years, and I would not rule out the possibility that run time got faster for some things but slower for others.
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Andy
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Re: Simulating Using PyLTSpice Takes Too Long
I have made contact with PyLTspice developer, and he pointed out that It could not be sped up further.
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Thank you for your attention
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Re: Simulating Using PyLTSpice Takes Too Long
On Sat, Mar 29, 2025 at 05:35 PM, <davitkharshiladze26@...> wrote:
LTSpice generates .raw output files, noramlly.
Correct.
I am using PyLTSpice tp prepeare netlist before simulation. I am manually writing the netlist.
Hmm.? I see some confusion there.? Do you manually write the netlist, or does PyLTSpice write or alter the netlist?? Obviously, if PyLTSpice needs to add .NET commands, it must be writing a netlist file (perhaps after reading one without the .NET commands), so that could be one place where some delay gets added.
After simulation, I am gathering .raw files and reading info from them.
Do you mean that you manually gather and read the .raw files?? Or does PyLTSpice have a hand in doing that?
I also use PyLTSpice to directly run the simulation after the netlists are prepeared:
Got that.
LTC.run runs the simulator and LTC.wait_completion() waits for .raw generation to finish. ...
Hmm.? That sets off alarm bells in my head.? How does PyLTSpice actually wait for LTspice to finish generating the .raw file?? Does it periodically probe the .raw file, looking for some sort of signature indicating that it is finished?? Does it wait until no further writing happens to the .raw file for the last, I don't know, let's say 15 seconds?? Does it examine the .log file waiting for a completion signature, and then post-process the .raw file?? Does it wait for Windows to signal that the process it was asked to run (running LTspice) has finished?
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Any of these things MIGHT introduce delays, anywhere from milliseconds to dozens of seconds, depending on what it does and how.
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The runtime of these 2 functions are approximately 1 second, which is way too much for my purposes.
What 2 functions are you talking about?
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How much time is acceptable?
I feel like normal LTSpice simulation takes about the same time, though, as I mentioned, it is harder to measure
Now this is where I get really confused.
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I think you're saying that it takes the same amount of time for LTspice to run a simulation, as it takes for PyLTSpice to run the same simulation.
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Is LTspice being run in so-called "batch" mode (with the "-b" switch), so that it omits all the screen graphics?? If you aren't doing that, then perhaps the extra overhead happens when LTspice takes the time to open a schematic window and a plot window and scale its axes.? You don't need it to do that if you plan to only post-process the .raw file's data.
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Andy
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Re: Simulating Using PyLTSpice Takes Too Long
1 second is too much for my purposes, and runtime is 1 second whether I use LTspice or PyLTspice? to run the simulaiton
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Re: PTC model with internal temperature rise
On Fri, Mar 21, 2025 at 01:48 PM, <pilou@...> wrote:
Sorry I'll uptload it again later.
It's OK now, I just uploaded it.
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Re: Simulating Using PyLTSpice Takes Too Long
Sorry, I see that the author of PyLTSpice does not know how to spell "LTspice".
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LTspice has no capital "s".? It is spelled "LTspice".
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PyLTSpice has a capital "S".
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Humph.
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Andy
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Re: Simulating Using PyLTSpice Takes Too Long
Help? me understand the problem.
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<davitkharshiladze26@...> wrote:
... However, simulation takes too much time. It takes 1 second for the simulation to complete. ...
Is 1 second too much time and that is what you want to reduce?
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Or is 1 second small, and adding PyLTspice causes the total time to be much greater than 1 second?
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Andy
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On Sat, Mar 29, 2025 at 05:41 PM, alan victor wrote:
Use the educational examples, oscillators, Colpits and remove the resonating inductor leaving the active device and passive feedback?
elements in place. ...
I might be wrong, but I think alan is referring to one of the example schematics that installs on your computer's disk when you install LTspice.
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...\examples\Educational\Colpitts.asc
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Andy
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On Fri, Mar 28, 2025 at 11:53 AM, <sebastian.herrera@...> wrote:
Dear all, I am trying to simulate a circuit with negative conductance using transistors and passive components. Does anyone have a circuit for this?
Use the educational examples, oscillators, Colpits and remove the resonating inductor leaving the active device and passive feedback?
elements in place. Do a scattering parameter operation and note the modulus of S11 is > unity over the range of potential frequency
of operation. This yields negative conductance. Note there is a nice peak in negative G value in the 1-10 MHz range and extends out to ~ 40 MHz.?
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Re: Simulating Using PyLTSpice Takes Too Long
LTSpice generates .raw output files, noramlly.
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I am using PyLTSpice tp prepeare netlist before simulation. I am manually writing the netlist.
After simulation, I am gathering .raw files and reading info from them.
I also use PyLTSpice to directly run the simulation after the netlists are prepeared:
? ? ? ? t1?=?time.time()
? ? ? ??LTC.run(netlist=netlist_filename)
? ? ? ??LTC.wait_completion()
? ? ? ??print(f"{t1?-?time.time()}?- Simrun")
LTC.run runs the simulator and LTC.wait_completion() waits for .raw generation to finish. Afterwards i can read these files for my desired outputs.
The runtime of these 2 functions are approximately 1 second, which is way too much for my purposes.
I feel like normal LTSpice simulation takes about the same time, though, as I mentioned, it is harder to measure
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k6whp
LV