I understand, that with the proper winding configuration, that a 90 degree phase shift can be achieved between primary and resonant secondary. That is done with a tapped secondary on a FM discriminator transformer. What are the guidelines and requirements needed to construct such a transformer at a given frequency OTHER than the standard 10.7Mhz? Say, on a form in the one inch diameter region, and frequency below 1Mhz? Ideal coil diameter, length based on chosen frequency? Turns / inductance (no resonating cap)?
You need LL high enough (k low enough) that the resonant tank, at whatever Q it ends up at, doesn't draw an excessive amount of current (excessively double-humping that stage's IF response), without being so high that the signal is too small. Just basic IF transformer and bandpass filter stuff.
Well, you generally get best results with a coil 0.5 to 2" long, pitch twice the wire diameter. Assuming that the form is 1" as stated. That's true of coils in general; were you expecting something specific to this application?
Depends on circuit impedance, but easily figured from the nature of the network.
On a sunny day (Mon, 29 Jul 2013 05:56:05 -0700) it happened RobertMacy wrote in :
It is actually really simple: Find a nice C value, 220 pF is my favorite. Use online calculator to find L for resonance, or estimate from Xperience. Use standard coil formers (8 mm diameter, or 6 mm diameter, whatever), with adjustable cores. Add some turns (how about 100? for 1MHz), apply your F from source or generator. Tune for maximum.
Now make 2, put them, 1 cm next to each other, wind 5 to 10 coupling turns from the first one, your LF comes from that. do that diode thingy.
I have done it twice, for TV audio (was 5.5 MHz FM here, thing then needs to be very precise as else you get video rattle in the audio. (the 5.5 MHz came from the video detector). Did not take more than an hour to build and adjust.
Later they had TBA120 quadrature detector, ebay...
At 1MHz 4046 PLL should demodulate FM too, did an audio link with that.
Is it narrow band? Then that 2 coil thing is likely no good, and you MUST use a quadrature detector, Motorola once had some nice chips.
So need more info. In the same time you look that up you can try it out. LTspice is only for self-justification and to show customers ;-)
I like your, "JUST DO IT!" approach. Tens to result in working breadboards.
When LTspice first started out, seemed a bit like that. But now, LTspice has mutated into a generic super tool and has essentially scooped the SPICE simulation market for ease of use, accuracy, access to support, access to models [thanks to an intrepid individual in Russia, Alex Bordodynov]
I use LTspice extensively for modeling EVERYTHING, from electromechanics to cabling to EMC/shielding to ESD protection, even antenna designs, etc. which contain NO Linear components.
And now with Mike's new updated version... On a particularly mind boggling topology that I've been working with since 1989! LTspice predicted at
100Hz there would be 35nV/rtHz noise and the breadboard had an actual MEASURED noise of 36nV/rtHz!!! Considering that S/N is the next frontier for improvement in my circuitry, LTspice is USEFUL! I used to be reduced to soldering/resoldering, head scratching until hair was gone, and then repair repair repair the !@#$#!@#$ overworked breadboard; now, can sit and explore all kinds of 'improvements' to the topology ...using LTspice. and even better, keep a record of the attempts. Breadboards tend to get lost/destroyed along the way.
If you're goinng to pick on simulation tools that are self serving, you should go after National and their online tool for SMPS design, with so many 'unknown to you' approximations you're likely;, as happened to me, to get wrong results. And, Analog Devices who likes to make horrific, 'unstable' models, or TI who likes to make TINA-only models. I'll stick with any company that has the courage to be 'opensource'.
On a sunny day (Mon, 29 Jul 2013 07:04:15 -0700) it happened RobertMacy wrote in :
Oh, I use LTspice, usually for small sub-circuits, but hey, human mind has a trillion ? of neurons (or it should be ;-)), and more than 60 years E design experience in my case. I just think differently. For example in case of 'coil', if you get ONE reference coil say 220 pF at 6 turns = 25 MHz, then, as w^2.L.C = 1, and L goes up as the square of turns.... you could estimate that for 1 MHz and 220 pF, 6 x 25 turns = 150. But some will be over-wound, closer space, 100 would be enough, and that would be with core half in. No LTspice, no online calculator, no complicated math, just some weapons of math destruction, wind the 100, and you are done. I wind 100 faster than I can write this. And 100 you know, as the grocer says when weighting the cheese: Can it be a little more? It is easy to remove a few turns... if you end up too high.
Now, now it works, you can ask the online calecujilator what L is for 1 MHz, and put the in LTspice, and show it to customer, he (the custardtomer) now feels much more secure after seeing 'mathematical proof'.
Hey I just had a discussion at CNN.com. and found out how to get rid of the US deficit: Advertising on dollar bills, on banknotes, how much does google make ... FED can do it too. Made available to all for free. (And in that discussion I invented gambling on banknotes too). So there you are, I like LTspice, in runs in wine (that is a windows emulator for the microsof users), so I can actually use it. It is the best I have seen (LTspice, not wine).
I know. I saw the 'smiley' I just used the opportunity to vent my spleen on three entities that should know better.
Using my own brain? I pride myself on looking at a schematic and actually view it 'moving' Instantly see what it does, where it's weak, etc. But, this topology has driven me NUTS! Using my intuition to increase bandwidth, the change reduces bandwidth. Increase gain, nothing happens - constant gain! I sat with a tablet of equations for two days solid to no avail, even with super simplifications. Now even with LTspice this !@#$#@! circuit doesn't 'act' right! where the circuit should null and be the same voltage, it's not! I'm starting to simply take the attitude, it works, because it works.
I carry 'data points too, especially the 'stacking factor' and coil cross section size.
Great ideas!! If Facebook can turn a profit of $480M in this economy then the govt should be able to do the same thing!
Uh, who paid that $480M? and, did THEY make a profit? Who's spending this money?
That's already being done, sorta: About $0.05/ea. One of the local Pizza houses was passing them out recently.
However, it might be possible to do what the various baseball and football stadiums have done for many years. Like renaming the stadium after major sponsors, we should rename government buildings, programs, and monuments after corporate sponsors. Instead of the white house, it should be the Verizon house, or something equally disgusting. Instead of naming airports and freeways after famous politicians, they should be named after corporate sponsors. For example, the Starbucks freeway.
Jeff Liebermann email@example.com
150 Felker St #D http://www.LearnByDestroying.com
On a sunny day (Mon, 29 Jul 2013 08:45:27 -0700) it happened RobertMacy wrote in :
Yes that is always that question, there is the issue of market share too, no advertising and people will forget you exist...
As to the math and circuit thing,. I see it very much this way: A baseball player will throw or catch a ball, neural net.. A mathematician will need to know every freaking detail, altitude, speed, air pressure, size, material, wind direction, etc etc... and then spend the next few hours calculating, and the ball, well the ball will be lost. There were a few students some time ago who build a ball catching machine, I think it was on youtube, really cool, but very controlled setup of course.
But, having programmed some neural nets, neural nets can give really bad answers too... It is a matter of training, and topology, a research area really.
The way we teach the next generation is for a large part by spoon feeding them the equations. without them having that 'hand on' experience that the baseball player has so to speak. A parrot is not a good designer. Luckily there are genetic variations and ever so often somebody is born and left intact enough to get humanity a bit further..
Test boards I make usually simply work (apart from wiring errors), and I made many in the past and took almost as many apart again, just fun to get something working, deepening understanding (as weights in the neural net, not always - or usually not, as mathematical models).
There is software too, in one way it is mathematically 100% exact, so a bit of both. I am not against math or something, just see it as a sub-circuit, a SMALL sub-circuit, in the human neural net. The 100 turns I came up with with w^2.L.C blah blah is justification, the 100 comes from the neural net. I have wound so many coils in my life I definitely did a 1 MHz one once... Was that not one of the first, a MW crystal radio? shift in ferrite rod for tuning.