I like the measurement-based approach. Hobby electrical engineering shouldn't worry about standardization and manufacturability. It's much more important to know how to cobble something together in the coming ruins of civilization, using scrounged and horded parts. :-)
Also, difference between Butterworth and Chebychev filters is just component values. The transfer function poles are moved inward on the S-plane for a Chebychev. This gives sharper roll off at the expense of more ripple in the pass band. I like to design Chebychev for output low pass filters because you don't usually care about ripple much and get a bit better attenuation. You should also note response at the 3rd harmonic as well as 2nd harmonic as often most of the distortion is at 3rd harmonic 5th, (odd) etc.. Good news is 3rd is farther away so much easier to attenuate. You get 2nd (and evens) when waveform is not symmetrical tops vs. bottoms of wave form. Good job with junk box parts! Looking forward to more of this kind of project!
Good filter. I build a lot of these kind of things and have a complete stock on hand of all the common Amidon powdered iron cores. The filter in that paper you showed used T37-6 cores which are MUCH smaller in diameter and thickness and so have lower AL value (inductance per turn). Those you have look like T80-? or so (much larger). Yes, the yellow can mean type 6 material but from a junk store who knows?? The fact that those cores seem to work at 7-14 MHz tells me they probably are type 6 (from Micrometals) material.
It is a very interesting video with the experimental filter design. If you are also not to patient (what I assume) to see the reactions on changes of element values, get a permanent magnet close to the relevant inductor core to decrease its value by saturation in the range of about 0 to -30% depending on the distance. For the final adjustment the number of windings shall be changed as it was done where the inductivity is proportional to n^2.
Cool, it seams a Pultec EQ has multiple windings on one core. various values of inductance on a single toroid. How do you know if you got the right size toroid. How do you determine the crossection of the wire, i got a roll of 0.5mm.
In my experience, steel wool is best for cleaning the insulation off of enamel coated wire, Just put the wire inside the wool, then squeeze the wool on the wire and rotate back and forth. Also, That "ARRL Handbook" looked very useful, could you do a brief explanation on what it covers? I'd be very interested in getting good reference material!
How would I go about tuning a filter circuit without the big equipment. I'm new to filters and have a couple that are out of whack. Is it possible with an antenna analyzer? If you know of videos, please direct me. I haven't seen many.
Are you going to consider a low pass diplexer output filter ? I've heard that these are better. Instead of reflecting the 2nd and 3rd harmonics back to the output device causing problems, the low pass diplexer re routes these harmonics to a load. www.qsl.net/wm5z/qex199907.pdf
I like the measurement-based approach. Hobby electrical engineering shouldn't worry about standardization and manufacturability. It's much more important to know how to cobble something together in the coming ruins of civilization, using scrounged and horded parts. :-)
What a great demonstration of rather simple construction of a low-pass filter. Enjoyed it a lot. Look forward to the next episodes.
Also, difference between Butterworth and Chebychev filters is just component values. The transfer function poles are moved inward on the S-plane for a Chebychev. This gives sharper roll off at the expense of more ripple in the pass band. I like to design Chebychev for output low pass filters because you don't usually care about ripple much and get a bit better attenuation. You should also note response at the 3rd harmonic as well as 2nd harmonic as often most of the distortion is at 3rd harmonic 5th, (odd) etc.. Good news is 3rd is farther away so much easier to attenuate. You get 2nd (and evens) when waveform is not symmetrical tops vs. bottoms of wave form. Good job with junk box parts! Looking forward to more of this kind of project!
What a fun video! Love the "probably should spice this" sometimes it's better to play as you retain more.
A very simple way of reducing the coupling between the inductive elements of such a filter is the rotate the middle inductor by ninety degrees.
Good filter. I build a lot of these kind of things and have a complete stock on hand of all the common Amidon powdered iron cores. The filter in that paper you showed used T37-6 cores which are MUCH smaller in diameter and thickness and so have lower AL value (inductance per turn). Those you have look like T80-? or so (much larger). Yes, the yellow can mean type 6 material but from a junk store who knows?? The fact that those cores seem to work at 7-14 MHz tells me they probably are type 6 (from Micrometals) material.
You're lucky you have a "junk" close by!
It is a very interesting video with the experimental filter design. If you are also not to patient (what I assume) to see the reactions on changes of element values, get a permanent magnet close to the relevant inductor core to decrease its value by saturation in the range of about 0 to -30% depending on the distance. For the final adjustment the number of windings shall be changed as it was done where the inductivity is proportional to n^2.
Cool, it seams a Pultec EQ has multiple windings on one core.
various values of inductance on a single toroid.
How do you know if you got the right size toroid.
How do you determine the crossection of the wire, i got a roll of 0.5mm.
In my experience, steel wool is best for cleaning the insulation off of enamel coated wire, Just put the wire inside the wool, then squeeze the wool on the wire and rotate back and forth. Also, That "ARRL Handbook" looked very useful, could you do a brief explanation on what it covers? I'd be very interested in getting good reference material!
ua-cam.com/video/OBNl-6nFyL0/v-deo.html
How would I go about tuning a filter circuit without the big equipment. I'm new to filters and have a couple that are out of whack. Is it possible with an antenna analyzer? If you know of videos, please direct me. I haven't seen many.
Nice video, very informative. What is the "junkstore" you mentioned? Sounds like I should have one also. HI HI . 73 Leo
www.excesssolutions.com
I enjoy these projects very much. How do you measure the input 1 mw maximum level to input signals for the TinySB measurements?
use a power meter, or start with a large attenuation and check, then lower the attenuation to a good level.
why is it called 40m or some x distance meter band,is it wavelength of the signal?
7 MHz frequency = 40m wavelength
actually 42.827494m but they round it off
Where is this junk store you speak of
excess solutions
san jose, ca
Are you going to consider a low pass diplexer output filter ? I've heard that these are better. Instead of reflecting the 2nd and 3rd harmonics back to the output device causing problems, the low pass diplexer re routes these harmonics to a load. www.qsl.net/wm5z/qex199907.pdf
Nice theory project! #1. Don't mention to the wife about going back to the junk store. Also ,does the junk store have a website or email? ;);)
www.excesssolutions.com/