FesZ Electronics is a channel about various electronic projects I spend my free time doing. It will go from educational stuff like tutorials, to teardown reviews to just putting ideas into practice. The point is to do something with educational value, not just fun. Have a look, leave a comment and come back again if you like what you've found!
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To get the negative resistance higher, cant you attenuate the amplifier gain downward by adding a feedback resistor? That is a resistor across the input and output of the amplifier.
Excellent video ! I appreciate your clear and thorough approach. This technology cannot be replaced by SDR when power is involved eg. in a transmitter. Keep up the good work !
I would have liked to see the design of those two sample filters you created. Design, construction, and testing. That would make a interesting video. For instance how did you spec out the size, positioning of the internal components & how to make any adjustments (presuming its possible with the construction method used.
great video many thanks... talking about amateur radio "abuse" of these things I have heard of aluminium beer kegs successfully being used as the conductive "cavity" for a VHF filter but the best one was a April fools joke about a 30' shipping container for a 7MHz (40 metre) cavity filter.
@@Dazzwidd standard length 40 & 45 foot shipping containers should easily contain a 33 foot 7MHz quarter wave resonator.. but I do agree that finding a "dunk tank" big enough to silver plate it might prove a little difficult 🤪.... I just don't know how I'm going to find a suitable filter for my stacked & bayed rotatable rhombic antenna farm.
Do a search for the "Kellermann Balun". It might be of interest to you and others, possibly try to simulate it and figure out how it works, the theory behind it. I contacted a few people on the subject, not much was given out. I'm a retired RF engineer, and also a Radio Amateur for 50 years. If I get the time I will also build one to test. Mind you that it is a 1:1 Balun. From what I can understand, it will handle plenty of power, depending on the size of the coax used, eg: rg142 or rg393. Should be a perfect Balun for a Balanced Tuner, on the input side of course, 50 ohms unbalanced in , output balanced.
Super interesting as always. Question: the 50 ohm source impedance in the models should be in series no? Or what is the effect of having this resistor in parallel with the voltage source?
When modeling a voltage source, this is comprised of an ideal voltage source with a series resistor; when modeling a current source, its comprised of a ideal current source with a parallel resistor. If you add the resistor in parallel with an ideal voltage source it will have no effect (same for a resistor in series with the current source); from the "outside", an ideal voltage source, or an ideal voltage source with a parallel resistor behave in exactly the same way.
@@FesZElectronics Yes, yes! But at 5:30 you are using voltage sources. Therefore my comment . Thanks for this quick answer, and for your excellent videos!
With voltage sources, if you right click on them directly, or going to "advanced", you have the option of defining the parasitics - series resistance and parallel capacitance; in the simulation, you can see under the "AC 1" parameter definition, the text "Rser=50" which is part of the voltage source definition -so the 50ohm series resistance is included into the voltage source, it does not have to be a dedicated external resistance.
The component datasheet will usually give an interval; also the beta is current, temperature and Vce dependent; usually, to be safe, you should determine the realistic extreme values of beta (both maximum and minimum), and make sure the circuit works for both.
having seen this some time ago in one or some of Curious Marc's vids, this is finally building the missing link to this dark art of trolling the rest of electronics!
What?! How come I find out you're Romanian only now? You should have seen the look of shock on my face when you pulled out that electronics book... Te salut!
The coupling is usefull to cancel the differential inductance; in general, the differential current is very large compared to the common mode one, so any inductance that interacts with the differential current needs to be able to not saturate - this limits the realistic values that can be achieved - usually 10-100uH; with a CMC, since it only interacts with the common mode current, which is very small, inductance values can go in the 100uH-22mH; such large values would not normally be feasible as uncoupled inductors which do not saturate.
Hi. I had very accurate working model of vacuum tube 12AX7. After refreshing my PC new installation (with new blue buttons tool bar) doesn’t run old saved files with tubes. Do you know what is the issue?
You can check if the model is corectly linked to the simulation - there should be an ".include" or ".model" statement with a link somewhere in the simulation - maybe the link changed; if its something else, you could post the exact error that you are getting.
I went ahead and implemented these two features as components (source-like constraints) that can be placed in LTspice. The "Iconst" current constraint can be placed in series with a source, whereas the "Vconst" voltage constraint can be placed in parallel with a source. Example test-jigs included in the zip Link to the library: drive.google.com/file/d/1I3VxgBCDz8ntf56d5Q9Zr3E13vShVpg9/view?usp=sharing
The crystal model used is called the Butterworth Van Dyke (BVD) model. The model can be extended by adding multiple RLC circuits along with a single parallel capacitor to model the primary and secondary resonant and anti-resonant frequencies. For sonar usage, widening the band between the resonant and anti-resonant frequencies by addition of series and parallel inductance is an underutilized method for achieving better performance...
I don’t know what other channel that I watch every new video start to finish as soon as it drops. Another fantastic video! I was part way through building a superhet transceiver by building each module, and the crystal filter was the most fun to build.
Hi there for the demonstration of the filters with the sdr software with rtlsdr hardware there are horizontal lines in the waterfall which oszilate a bit over time. If i am not mistaking i would think this could be the automatic gain control adjusting amplification making the comparism wrong. What do you think?
I guess that there are some very strong signal appearing that are overdriving the pre-amplifier, or just the input stage, and then it behaves as if the AGC is still on; or maybe its just a protection mechanism that cannot be turned off. I'm not sure what happened.
Is order of the filter the only reason why there were some extra spikes in the filter response ? Or is it also because of the imperfections in the crystal ? Also how can we get rid of those spikey responses ? Excellent video though.
The spikes are caused by the imperfections in the crystals, but my assumption is that a higher order filter would filter these spike out since each crystal has its imperfections different from other crystals.
Why did the first filter not make much of a difference in the SDR graph? Based on the plot of the filter characteristics I expected a much better result.
I think the reason is that most major noise sources (like FM ~100MHz and GSM ~800MHz) are too far away to affect the operation of the SDR; I've seen a far more clear difference and improvement when building filters for the 2m band (~145MHz) since that is very close to the FM band and the Air Band - and filtering these out creates a major improvement.
@@FesZElectronics He wants one he likes. That he didn't offer any specific suggestions at all means he gave it no thought and doesn't really care in the first place. BTW, there's nothing wrong with your greetings. Ignore this guy.
Do you mean the 10.7MHz ceramic resonator? I used the same resonator in both measurements (with and without the 220R resistors); unfortunately I do not have a datasheet or order code for this component since it was just a random component I found in a box
Me too. Mine was one of my most useful tools, although I've pretty much switched to using a NanoVNA because of all of the info provided across a wide frequency range in just a few seconds.
At 4:48 you introduced a diode across SW2 to ensure current is always flowing through the inductor. How does the diode achieve this? Its anode is at ground so the only way for it to conduct is if Vs2 < -0.6V rigbt? Why is that node swinging below ground when it wasn't before (the only change is that you introduced the delay). Is it that with the delay, the left hand side of the inductor would be floating for a short period of time, changing its voltage to try and keep current flowing, and the diode now allows current to flow from ground, and into the inductor?
The inductor current in a buck converter will always flow from the switching node towards the output; when the high side switch is on, the inductor behaves like a load, getting charged with current, so the left side is at a higher voltage potential than the right side; when the high side switch is off, current still flows either trough the diode or the low side switch, an this time the inductor behaves like a battery - it is producing a voltage which is inverted to when it was behaving like a load - so the left side is at a lower voltage potential than the right; if the low side is an ideal switch, then that side of the inductor is at 0V; if its a real switch (with non-zero voltage drop) or a diode, the switching node goes negative - this is how the diode is being polarized.
Excellent video. Still one querry, in Frequency modulation , class C amplifier is used . Whether full sinusoildal Wave is the output of Class C amplifier or a limited angle ( less < 2 pi ) is used ? Thanks
