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Re: Trying to simulate a 27Mhz receiver. Couple of questions
¿ªÔÆÌåÓýThe real question in my mind is what an antenna model would do in simulation.?1. ?Do you want it to represent the actual terminal impedance of some real antenna? That, in itself, is challenging. EZNEC, referenced below, might help. 2. Do you want it to provide a signal to the receiver? If so, you can simulate that with a standard voltage (or current) source. 3. Do you want it to provide many signals over some band that you can ¡°tune in¡±? If this is what you want, there is a real problem ¡°tuning¡± the receiver during run time.? 4. Do you want many signals that you can use to test for ¡°adjacent channel¡± rejection? If so, you can simulate that with several standard voltage (or current) sources. Jim, KA7EHK James Wagner Oregon Research Electronics
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Re: Trying to simulate a 27Mhz receiver. Couple of questions
Robert Thomas
Re your antenna question --
Antennas can be very simple or very complex. But for example -- A simple center-fed half-wave dipole (about 17 feet long in your case) operated at its resonant frequency, and in free space or well away from everything else looks like a pure resistance of about 75 ohms. Incoming signals can be represented by a voltage source (modulated or otherwise) in series with this. A quarter-wave whip antenna (around 8.5 feet long in your case) on an ideal ground plane acts like half a dipole, so ideally looks like a pure resistance of around 37 ohms. These simple antennas have a useful bandwidth of a few percent; outside this range, they develop significant series reactance, and the resistance also changes. Depending on your situation, these simple antennas may be practical. If you want to look further afield, EZNEC? (eznec.com) is? a good antenna analysis program -- it comes in demo and paid versions, with a good manual and examples. As a general comment -- Making a small antenna is very easy. Making a good antenna is easy (see above) Making a good, small antenna can be very difficult. Hope this is useful Bob --- This email has been checked for viruses by AVG. |
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Re: LTSpice Model for Photo Triac - VOM160
Hi Andy, Thanks again so much for your help.I was able to save the part with name MOC3083 already on it.? But I wasn't able to do the automatic MOC308x.lib search. I tried the LTspice Help using "Model and Library Search Path" topic. I entered the directory path for the newly saved symbol MOC3083? and the directory path for MOC308x.lib and saved. But it didn't work or do anything. Still the schematic without the .lib MOC308x.lib directive wouldn't run. I also tried? the FAQ but can't find the right instruction there for the automatic directive search. But its ok already at this point. I can easily add the directive everytime I use the part.? Incidentally I might have to ask help also on loading another part if I can't still do it. But it will be on New Topic:). Thanks and best regards, Eric
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Re: Single supply VCO
For fun add this line to compare between MODULATE and the formal equation: a1 modulation 0 0 0 0 0 fm2 0 modulator mark={FC+DEVIATION} space={FC} Compare node FM to FM2.? With 1nS max time step I get less than 100 microvolt difference between the two.? No doubt the MODULATE device is more accurate since it is no doubt implemented internally in source code (C or C++). Dan |
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Re: fft and ltspice
Hello, A V-source can read its PWL-data from a file. Therefore place a V-source in the schematic. Then right-mouse-click on it and choose PWL-file. LTspice will interpolate between the data points, if the FFT has to calculate data points between the defined data points. If the simulation has finhshed, you can start the FFT. Right-mouse-click into the waveform window -> View -> FFT. Data format of the file: time value I guess space(s), comma and tab(s) are possible seperation characters. 2 0 2.1 -1 2.2 0.5 2.3 0 2.4 -0.3 2.5 0.0 2.6 -0.1 2.7 0 2.8 0 Best regards, Helmut |
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Re: fft and ltspice
The very simplest way to get data from MATLAB into LTspice is to use .wav files.? MATLAB can read and write wave files and LTspice can read and write these files.? See examples: C:\Program Files\LTC\LTspiceXVII\examples\Educational\wavein.asc C:\Program Files\LTC\LTspiceXVII\examples\Educational.waveout.asc Note: You have to look at the folder where you installed LTspice which might not be same as me. Good luck, Dan |
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fft and ltspice
ltspice group: hi? ?suppose i have a sine wave and i sampled this wave for example with Matlab software? so? i have samples of this wave and i save them for example in a text file. how can i do fft of these sample in ltspice( this work can be done easly in Matlab but i want do in ltspice) and how import the samples in ltspice? thanks |
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Re: Single supply VCO
Nekvstr, The MODULATE FM input works just like a numerically controlled oscillator.? It increments the phase in an internal accumulator based on the instantaneous frequency at each time step. It then takes the sin(phase)*AM to produce the output.? This is not complicated nor mysterious. Here is a simple netlist that implements the FM modulation equation without need of the MODULATE function.It modulates a 100kHz carrier with +/-10kHz deviation using a 1kHz modulating signal * FM Simulation B1 0 FM I=sin(2*pi*FC*time + 2*pi*DEVIATION*idt(i(r2))) R1 FM 0 1 I1 0 modulation SINE(0 1 {MF} 5m) R2 modulation 0 1 .param FC=100K .param MF=1K .param DEVIATION=10K .tran 0 40mS 0 100n .backanno .end Note that LTspice needs a "hint" to slow down the simulation by restricting the maximum time step so as to not skip ahead too much.? Otherwise the integrator idt() misses too much information. ?? |
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Re: Cannot download IR2117_test.zip because of certificate error
From here (eastern USA), the downloads work every time (assuming I'm starting from the webpage and that the webpage was recently refreshed.? But I have had those problems from time to time (not for the last few weeks).? Several successful downloads of that file, today. It appears that western USA is affected by this problem. The URL starting with "" came from the error message.? It wasn't where he started.? He started by clicking on the "Files" tab on the group's website. It's odd that the URL starting with "" was missing the VERY long stream of characters that they always have. My suggestion is to keep trying.? Usually when this happens to me, it's temporary, and intermittent.? So it might fail 75% of the time and work the other 25%.? But occasionally it fails on 100% of tries.? Make sure to periodically refresh the webpage where you click on the file. It MIGHT also depend on web browser (though I haven't seen any proof of this).? So, if you have another browser, try that too. Regards, Andy |
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Re: Single supply VCO
That's pretty much true.? There are a handful of (former) Linear Technology and Analog Devices employees here, but you're right that most of them don't know LTspice internals or its code.? However, Mike is still "here", though he visits here rarely (and pretty much in "write-only mode") so he is never going to see a question here directed at him. Andy |
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Re: LTSpice Model for Photo Triac - VOM160
Eric asked, "How do I now permanently save the part that has already MOC3083 on it instead of? LED_TRIAC_ZCS, ..." That's easy.? Edit the symbol and save it.? Open the symbol file in LTspice.? You can right-click on it when it's on your schematic, then click Open Symbol.? Then right-click on that text and change it.? It happens to be an Attribute of the symbol.? Then save the file.? If you want to, you could save it under a different filename, but then you'd probably want to edit your schematics too. ? ? "...?and what needs to be done?so I don't have to add the directive? ?.lib MOC308x.lib? everytime I use this part?" There are ways to put the library filename into the symbol itself, but to be honest I don't remember them.? I think there is more than one way, but they come with side-effects which is one reason why I tend to avoid it.? If you read through the LTspice Help (remember that?) it lists at least one of them.? I think one of the consequences is that you can no longer open or edit the symbol from a schematic page.? Which might not be an issue for you. Some of the symbol attributes work in unexpected ways. Regards, Andy |
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Re: Cannot download IR2117_test.zip because of certificate error
¿ªÔÆÌåÓýHelmut, ? With respect he didn¡¯t click on the temporary URL what he said was ? >????? ¡°I am trying to download the IR2117_test.zip file found under "Files"¡± ? So It would appear to me that he has gone to the ¡°files¡± page and found ¡°IR2117_test.zip¡± ? >???????? ¡°Clicking on the link takes me to website?¡±, ? That is what happens. All the links on the files page re-direct to ¡°xa.yimg.com¡± ? >????? ¡°This is what happens but I get error message?±··¡°Õ::·¡¸é¸é³å°ä·¡¸é°Õ³å´¡±«°Õ±á°¿¸é±õ°Õ³Û³å±õ±·³Õ´¡³¢±õ¶Ù¡± ? His browser does not recognise the certificate on the re-directed link. He never clicked on it, he was re-directed there. To which my answer is still ¡°no¡±. It seems to happen from time to time. ? Dave ? ? From: LTspice@...
Sent: 22 November 2018 10:39 To: LTspice@... Subject: RE: [LTspice] Cannot download IR2117_test.zip because of certificate error ? Hello Dave, ? Have you seen Tony's answer? He tried with the wrong web-address? One will get such temporay adresses with a right-mouse-click and "Copy link" on the filename in the Files section. ? The corerct address is below. IR2117_test.zip ? Best regards, Helmut |
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Re: Cannot download IR2117_test.zip because of certificate error
¿ªÔÆÌåÓýHelmut, ? Yes I have, but the problem is not related to the temporary nature of the link. What was reported was the error message from the web browser. When you click on:- ? ? and then on ? IR2117_test.zip ? It ALWAYS redirects to one of those temporary links. If there is an error the reported failed URL will be the temporary link to which you have been re-directed. In this case it was a certificate error. If there is a certificate error then the failing URL will always be one of those links and that¡¯s what the browser will report. You will NEVER get an error that shows the original URL. Re-visiting the links as per above usually hides the problem, I believe because ¡°xa.ying.com¡± ?is actually a load balanced cluster. When you repeat the process you usually get a different server and it works. ? Dave ? From: LTspice@... <LTspice@...>
Sent: 22 November 2018 11:03 To: LTspice@... Subject: RE: [LTspice] Cannot download IR2117_test.zip because of certificate error ? Helmut wrote: ? "Have you seen Tony's answer?" ? Maybe not, because most of my messages don't seem to get relayed by email; they are only visible on Yahoo! groups site. ? I use several different computers with different email clients, and I often find I don't receive quite a few messages - not just mine - by email. Sometimes I receive an answer to a question, but not the original question. I have to go to the Yahoo! site to see all the messages in a thread.
? Regards, Tony |
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Re: Cannot download IR2117_test.zip because of certificate error
Helmut wrote: "Have you seen Tony's answer?" Maybe not, because most of my messages don't seem to get relayed by email; they are only visible on Yahoo! groups site. I use several different computers with different email clients, and I often find I don't receive quite a few messages - not just mine - by email. Sometimes I receive an answer to a question, but not the original question. I have to go to the Yahoo! site to see all the messages in a thread. Perhaps it's because I access the Yahoo! groups with a non-Yahoo! email address? I don't know, but it used to work properly, years ago. Yahoo! is now just basically unreliable. If my business depended on Yahoo!, I would find a new provider. Regards, Tony |
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Re: Cannot download IR2117_test.zip because of certificate error
Hello Dave, Have you seen Tony's answer? He tried with the wrong web-address? One will get such temporay adresses with a right-mouse-click and "Copy link" on the filename in the Files section. The corerct address is below. IR2117_test.zip Best regards, Helmut |
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Re: Cannot download IR2117_test.zip because of certificate error
¿ªÔÆÌåÓýProbably not the only person. The error says your PC does not trust the certificates on xa.yimg.com. I have seen several reports of this here and on other groups. The info you have given is not enough to know if the error is with the server which has an invalid certificate, or with your PC which is missing a root certificate, or if you are in a commercial environment and there is a proxy that¡¯s messing things up ? E.g. ? https://superuser.com/questions/1083766/how-do-i-deal-with-neterr-cert-authority-invalid-in-chrome ? Hopefully clearing the browser cache and starting from the top of the files section will sort things out. If not make sure your browser is up to date. It looks like you are using CHROME and chrome needs to be up to date for its certificate checking to work reliably¡ Also note that xa.yming.com will actually be an array of load balanced servers so it could just be one has of the array has some issue. If so some times it will work and at other times it won¡¯t. ? .. hope this helps.. ? ? Dave G4UGM ? ? ? ? ? ?
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Re: Cannot download IR2117_test.zip because of certificate error
vermaak.jj@... wrote: "I am trying to download the IR2117_test.zip file found under "Files" Clicking on the link takes me to website?, but I get error message?NET::ERR_CERT_AUTHORITY_INVALID Am I the only one that cannot access the download files under TAB Files?" That sounds a bit like paranoia... The URI you posted is incomplete, and in its entirety, is a transient URI valid for only a short time, and likely valid for only one user - this is a peculiarity of Yahoo! platform, and frequently causes consternation in this group. The real URI for the file you seek is: Clicking on this link will probably just take you to Files > Lib. Use Ctrl-F to find the file on that page, which is quite long. I just checked it and the file you seek is there and downloadable. Regards, Tony |
Tony Casey