|
toroid cores?
Hi Newsgroup,
Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. If I end up using an air core, would I keep the ratio of turns for the tickler and injection coil? (where he has 3 and 5 turns spec'd) ? It's my assumption that in these two smaller coils, it's a step up transformer so it'd be a matter of ratios, am I correct in this assumption? Every bit of the circuit should come from garbage (the MPF102's I had to buy, but thats it) Even the coil wire is from the transformer of a broken microwave, the LM386 chip used for audio (and some resistors) will come from an old modem and the pot is a 500k pot, (from a console) wired in parallel with a ~10k resistor to give a range between 0 - 10k ohms. The main point is to build it from garbage, I already have a radio and don't really "need" one, but.. as I once built a tube version of this (far simpler) doing one in solid state appeals to me. Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
toroid cores?
Check this page from Amidon Associates. They are a great supplier of
toroids to the ham community! http://www.amidoncorp.com/aai_ironpowdercores.htm Looks to me like 25 turns on a T-50-2 core will give about 3 MICRO Henries according to Amidon's formula... Scott N0EDV Jamie wrote: Hi Newsgroup, Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. If I end up using an air core, would I keep the ratio of turns for the tickler and injection coil? (where he has 3 and 5 turns spec'd) ? It's my assumption that in these two smaller coils, it's a step up transformer so it'd be a matter of ratios, am I correct in this assumption? Every bit of the circuit should come from garbage (the MPF102's I had to buy, but thats it) Even the coil wire is from the transformer of a broken microwave, the LM386 chip used for audio (and some resistors) will come from an old modem and the pot is a 500k pot, (from a console) wired in parallel with a ~10k resistor to give a range between 0 - 10k ohms. The main point is to build it from garbage, I already have a radio and don't really "need" one, but.. as I once built a tube version of this (far simpler) doing one in solid state appeals to me. Jamie |
toroid cores?
Jamie wrote:
I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Yes, I would expect they would be really bad ! If you knew the permeability of the material used then measuring with a ruler and applying some math (I don't know the formulas) would in theory get you an iductance calculation. But the materials used for these EMI chokes generally has too high a permeability to make inductors with convenient numbers of turns for the HF bands, and generally is quite lossy so the resulting inductors will have low Q. It is extremely unlikely to work. Since you don't want to buy any parts, I would recommend once you figure out the required inductance from the Amidon formulas, just wind air core coils (well, some sort of low loss former like a piece of plastic tubing is probably needed) with the same inductance. Inductance formulas for air core coils are available everywhere in handbooks and on the web. You might have to play with the number of turns in the feedback link though, as the coupling between it and the main coil will not be as tight in an air core coil as in the toroid. I would start with the same ratio of turns or maybe add a bit to the feedback coil. 73, Steve VE3SMA |
toroid cores?
On Fri, 14 Jul 2006 09:42:06 GMT, (Jamie) wrote:
Hi Newsgroup, Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. 23-25 turns (or 50 total) on a T50-2 would be more like 20 uH (micro henries). If you using a ferite intended for noise suppression then its likely 43 ot 71 material and not suited for RF tuned circuits. If I end up using an air core, would I keep the ratio of turns for the tickler and injection coil? (where he has 3 and 5 turns spec'd) ? It's my assumption that in these two smaller coils, it's a step up transformer so it'd be a matter of ratios, am I correct in this assumption? Every bit of the circuit should come from garbage (the MPF102's I had to buy, but thats it) Even the coil wire is from the transformer of a broken microwave, the LM386 chip used for audio (and some resistors) will come from an old modem and the pot is a 500k pot, (from a console) wired in parallel with a ~10k resistor to give a range between 0 - 10k ohms. The main point is to build it from garbage, I already have a radio and don't really "need" one, but.. as I once built a tube version of this (far simpler) doing one in solid state appeals to me. Why not wind the coil on a toilet paper cardboard tube, pill bottle, or peice of PVC pipe scrap? Allison Jamie |
toroid cores?
Jamie wrote:
Hi Newsgroup, Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. If I end up using an air core, would I keep the ratio of turns for the tickler and injection coil? (where he has 3 and 5 turns spec'd) ? It's my assumption that in these two smaller coils, it's a step up transformer so it'd be a matter of ratios, am I correct in this assumption? Every bit of the circuit should come from garbage (the MPF102's I had to buy, but thats it) Even the coil wire is from the transformer of a broken microwave, the LM386 chip used for audio (and some resistors) will come from an old modem and the pot is a 500k pot, (from a console) wired in parallel with a ~10k resistor to give a range between 0 - 10k ohms. The main point is to build it from garbage, I already have a radio and don't really "need" one, but.. as I once built a tube version of this (far simpler) doing one in solid state appeals to me. Jamie There are toroid cores that would work quite well for this, but the characteristics of the core depend heavily on the core material. It can be very difficult to characterize a mystery core. I suggest you look in the ARRL handbook for the appropriate coil formula (or search the web) and make a single-layer air core coil on an appropriate-sized form. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html |
toroid cores?
In ,
Tim Wescott mentions: wrote: Jamie wrote: I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Yes, I would expect they would be really bad ! If you knew the permeability of the material used then measuring with a ruler and applying some math (I don't know the formulas) would in theory get you an iductance calculation. But the materials used for these EMI chokes generally has too high a permeability to make inductors with convenient numbers of turns for the HF bands, and generally is quite lossy so the resulting inductors will have low Q. It is extremely unlikely to work. Since you don't want to buy any parts, I would recommend once you figure out the required inductance from the Amidon formulas, just wind air core coils (well, some sort of low loss former like a piece of plastic tubing is probably needed) with the same inductance. Inductance formulas for air core coils are available everywhere in handbooks and on the web. You might have to play with the number of turns in the feedback link though, as the coupling between it and the main coil will not be as tight in an air core coil as in the toroid. I would start with the same ratio of turns or maybe add a bit to the feedback coil. 73, Steve VE3SMA If it's a broadcast band radio a toilet paper tube will work well. If ham band then something smaller like a sample-size shampoo bottle. Does it count as garbage if you buy the stuff so you'll have the 'garbage' when you're done? LOL! I was sooo tempted to buy 0.05 resistors after burning my fingers trying to extract them from a modem.. :-) I read some place, it's better to use a larger diameter coil if at all possible, but the formulas I've run across for calculating uH (I always get my milli's and micros confused!) seem to indicate in either case, I'd need the same amount of wire. Lots of things puzzle me about this, for example in this circuit: http://www.tricountyi.net/~randerse/regen.htm I don't see a "grid leak" the way I had used in the tube model. While this circuit: http://www.electronics-tutorials.com...o-receiver.htm Seems to have one feeding the gate of the FET. (never was real clear on what it did exactly) (I can't use the latter circuit as it has more parts and I don't want to introduce a 3rd variable cap.) Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
toroid cores?
The inductance of a toroid, in MICRO-henries, is -
L = 0.6283 * Mu * Square( N ) * B where B = D1 - Squareroot( Square( D1) - Square( D2 ) ) Mu = permeability of core material. N = number of turns. D1 = mean diameter of ring in metres. D2 = diameter of ferrite core material in metres. If the core is not circular, use the equivalent diameter which has the same cross-sectional area. To calculate number of turns just rearrange the formula. To obtain high Q, you MUST use HF grade permeability material. Permeability can be calculated using the formula by winding some turns on a core and measuring inductance. A very good instrument to use is an Autek RF Analyst-1 But, of course, if you are able to measure inductance there will be no need to calculate permeability. You can calculate the required number of turns immediately. ---- Reg. |
toroid cores?
In ,
Scott mentions: Check this page from Amidon Associates. They are a great supplier of toroids to the ham community! http://www.amidoncorp.com/aai_ironpowdercores.htm Looks to me like 25 turns on a T-50-2 core will give about 3 MICRO Henries according to Amidon's formula... Whew! thanks! My assumption that it was 300 yielded some pretty far out number of turns for air coils, like 72 or something I seem to recall. Looks more like 7-8 turns on a cylinder 2.5" in diameter? (that seems awful small to me) If the tickler coil is currently three turns, would I just leave it at that? Still, it's nice.. small enough I can probably use the "good wire" for shortwave. :-) (FWIW old microwaves are apparently an excellent source if copper wire, I'm tempted to use some of it for an antenna) If the capacitance in the tank circuit is ~25-400pF, and I use 3uH then the frequency response will be about: 4.5mhz - 14mhz ? (does that sound right?) This must be why the others I'd looked at involve pluggable or tapped coils? (In general, is there an ideal ratio of capacitance to inductance for a given range? IE: could I just add parallel capacitance to lower the frequency or is it better to increase the coil or.. both? I notice as I run through some calculations, I need a LOT more uH to cover a smaller and smaller range of frequencies the lower I get. He states on his page that it picks up MW, (which is actually what I'm mostly interested in) but.. didn't mention anything about mixed coils. His circuit involves a "front end RF amp" (for a total of two coils) when using air, do I need to some how shield this second coil? I'm assuming it if it's perpendicular to the main one, thats enough?) Was hoping to avoid a large air coil because as it is now, the everything except the capacitors (and AF stuff) fit in a tunafish can for shielding. :-/ Still, the whole point is to assemble it from garbage. I might splurge and get some mechanical stuff for the tuner, but.. have to get it working first! (sure am glad I kept that signal injector, it's been really handy for this!) Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
toroid cores?
wrote:
On Fri, 14 Jul 2006 09:42:06 GMT, (Jamie) wrote: Hi Newsgroup, Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. 23-25 turns (or 50 total) on a T50-2 would be more like 20 uH (micro henries). Hi, Allison - I think you erred slightly. It's about 3 uH at 25 turns on a T-50-2. See Scott's post in this thread for a link to data and equation. Cheers, John |
toroid cores?
On Fri, 14 Jul 2006 16:05:42 GMT, John - KD5YI
wrote: wrote: On Fri, 14 Jul 2006 09:42:06 GMT, (Jamie) wrote: Hi Newsgroup, Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. 23-25 turns (or 50 total) on a T50-2 would be more like 20 uH (micro henries). Hi, Allison - I think you erred slightly. It's about 3 uH at 25 turns on a T-50-2. See Scott's post in this thread for a link to data and equation. For 23-25 yes, but I also postulated that was a tapped coil of 50T total. then I'm closer. But it was an eyeball guess as I didn't calculate it. I was only off by ~7 rather than 10,000. ;) Allison Cheers, John |
toroid cores?
Well, I'm not sure about a lot of the questions you asked, so I would
suggest waiting to hear from others for ideas or, in true hamming spirit, give it a go and see what happens :) I wish you good luck...it sounds like an interesting project! Scott N0EDV Jamie wrote: In , Scott mentions: Check this page from Amidon Associates. They are a great supplier of toroids to the ham community! http://www.amidoncorp.com/aai_ironpowdercores.htm Looks to me like 25 turns on a T-50-2 core will give about 3 MICRO Henries according to Amidon's formula... Whew! thanks! My assumption that it was 300 yielded some pretty far out number of turns for air coils, like 72 or something I seem to recall. Looks more like 7-8 turns on a cylinder 2.5" in diameter? (that seems awful small to me) If the tickler coil is currently three turns, would I just leave it at that? Still, it's nice.. small enough I can probably use the "good wire" for shortwave. :-) (FWIW old microwaves are apparently an excellent source if copper wire, I'm tempted to use some of it for an antenna) If the capacitance in the tank circuit is ~25-400pF, and I use 3uH then the frequency response will be about: 4.5mhz - 14mhz ? (does that sound right?) This must be why the others I'd looked at involve pluggable or tapped coils? (In general, is there an ideal ratio of capacitance to inductance for a given range? IE: could I just add parallel capacitance to lower the frequency or is it better to increase the coil or.. both? I notice as I run through some calculations, I need a LOT more uH to cover a smaller and smaller range of frequencies the lower I get. He states on his page that it picks up MW, (which is actually what I'm mostly interested in) but.. didn't mention anything about mixed coils. His circuit involves a "front end RF amp" (for a total of two coils) when using air, do I need to some how shield this second coil? I'm assuming it if it's perpendicular to the main one, thats enough?) Was hoping to avoid a large air coil because as it is now, the everything except the capacitors (and AF stuff) fit in a tunafish can for shielding. :-/ Still, the whole point is to assemble it from garbage. I might splurge and get some mechanical stuff for the tuner, but.. have to get it working first! (sure am glad I kept that signal injector, it's been really handy for this!) Jamie |
toroid cores?
In ,
Scott mentions: Well, I'm not sure about a lot of the questions you asked, so I would suggest waiting to hear from others for ideas or, in true hamming spirit, give it a go and see what happens :) I wish you good luck...it sounds like an interesting project! Thanks. Looks like I may have fried the FET. :-( No matter what I did, I simply could not get feedback. I hooked an LM368 audio amp pretty much directly to the RF signal generator and I could vaguely hear it, so... I'm thinking the reason it was working the way it did (with the "station" comming in stronger as I tuned it) was simply the LM386 acting like a detector in a TRF radio :-/ (The thing that confused me was, if I held an AM radio really close to the coil, I DID get some interference, but I couldn't hear a squeal in the speaker of my radio. I put it away for now, I do have another FET I could f^Htry, but.. I don't want to damage it. I was thinking about removing the pot entirely and using a rotating "inner coil" serve in it's place: +v ------ (tickler coil) --- [D|G|S] --- audio out (Basically using both sides of the FET) Hooking the tank circuit up to the gate, just as before but eliminate the parts for controlling the tickler, sort of like this: () with being the tank coil and the () being a coil inside the 's in such a way you could turn it, controlling the tickler by changing it's angle. I've seen old regen radios that appear to do something like this, but constructing a coil that can be turned (w/out changing the tank and input coil's value) look tricky. A plastic ink pen could be the shaft for turning it, but keeping it in the center w/out wobbling.. As the parts MUST come from garbage, precise values are hard to get. To remove them is a good thing. :-) Not today though.... Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
toroid cores?
Jamie wrote:
In , Scott mentions: Well, I'm not sure about a lot of the questions you asked, so I would suggest waiting to hear from others for ideas or, in true hamming spirit, give it a go and see what happens :) I wish you good luck...it sounds like an interesting project! Thanks. Looks like I may have fried the FET. :-( No matter what I did, I simply could not get feedback. I hooked an LM368 audio amp pretty much directly to the RF signal generator and I could vaguely hear it, so... I'm thinking the reason it was working the way it did (with the "station" comming in stronger as I tuned it) was simply the LM386 acting like a detector in a TRF radio :-/ (The thing that confused me was, if I held an AM radio really close to the coil, I DID get some interference, but I couldn't hear a squeal in the speaker of my radio. I put it away for now, I do have another FET I could f^Htry, but.. I don't want to damage it. I was thinking about removing the pot entirely and using a rotating "inner coil" serve in it's place: +v ------ (tickler coil) --- [D|G|S] --- audio out (Basically using both sides of the FET) Hooking the tank circuit up to the gate, just as before but eliminate the parts for controlling the tickler, sort of like this: () with being the tank coil and the () being a coil inside the 's in such a way you could turn it, controlling the tickler by changing it's angle. I've seen old regen radios that appear to do something like this, but constructing a coil that can be turned (w/out changing the tank and input coil's value) look tricky. A plastic ink pen could be the shaft for turning it, but keeping it in the center w/out wobbling.. As the parts MUST come from garbage, precise values are hard to get. To remove them is a good thing. :-) Not today though.... Jamie Hi, My luck (quite some time ago) with FETs was not nice either. Someone may have to correct my, yet the only way I think one can get away with fiddling with the things the way most people construct, might be to use zener diodes between the gate and source and drain. Once its all together and apparently functioning one probably could remove them then with less worry about then getting a little static jolt and ruining the junction. Tubes are a lot more forgiving. Sincerely, Gregory D. MELLOTT |
toroid cores?
Gregory D. MELLOTT wrote:
My luck (quite some time ago) with FETs was not nice either. Someone may have to correct my, yet the only way I think one can get away with fiddling with the things the way most people construct, might be to use zener diodes between the gate and source and drain. Once its all together and apparently functioning one probably could remove them then with less worry about then getting a little static jolt and ruining the junction. Tubes are a lot more forgiving. With tube stuff, touching the wrong thing will kill you. With sand stuff, touching the wrong thing will kill it. -- Mike Andrews, W5EGO Tired old sysadmin |
toroid cores?
In ,
"Gregory D. MELLOTT" mentions: My luck (quite some time ago) with FETs was not nice either. Someone may have to correct my, yet the only way I think one can get away with fiddling with the things the way most people construct, might be to use zener diodes between the gate and source and drain. Some day... I'm going to mess about wit zener diodes... I tried to always keep myself grounded, pinching the leads together with a hemostat, but.. maybe the soldering iron did it, yea, uh huh. :-) Once its all together and apparently functioning one probably could remove them then with less worry about then getting a little static jolt and ruining the junction. Tubes are a lot more forgiving. I hear ya about tubes being more forgiving, much more fun, too. Just wish they didn't have such weird power requirements. Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
toroid cores?
Actually, maybe the soldering DID do it. Are you using an iron with a
three prong cord? The third prong ties the soldering iron tip to ground (assuming that, if so, you are plugging that into a GROUNDED three prong outlet and not using one of those three prong to two prong adapters). Also, this is assuming you are in the United States...not sure about other countries outlet wiring. Scott Jamie wrote: Some day... I'm going to mess about wit zener diodes... I tried to always keep myself grounded, pinching the leads together with a hemostat, but.. maybe the soldering iron did it, yea, uh huh. :-) Jamie |
toroid cores?
Jamie,
Go to http://www.kitsandparts.com and use the toroid calculator he has there. Another thing you can try is wrapping 25 or 30 turns and then measuring it with an LC meter in the L mode of course. AADE sells a fantastic LC meter kit for about $100 - I built one a few years ago and I use it every week when digging in the junk box looking for caps and coils. Good luck with your regen, have fun. 73 de KB9BVN -- ========================================= Radio Amateurs - Fill your junk box, from my junkbox! http://www.hamradparts.com 73 de KB9BVN ========================================= "Jamie" wrote in message ... Hi Newsgroup, Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. If I end up using an air core, would I keep the ratio of turns for the tickler and injection coil? (where he has 3 and 5 turns spec'd) ? It's my assumption that in these two smaller coils, it's a step up transformer so it'd be a matter of ratios, am I correct in this assumption? Every bit of the circuit should come from garbage (the MPF102's I had to buy, but thats it) Even the coil wire is from the transformer of a broken microwave, the LM386 chip used for audio (and some resistors) will come from an old modem and the pot is a 500k pot, (from a console) wired in parallel with a ~10k resistor to give a range between 0 - 10k ohms. The main point is to build it from garbage, I already have a radio and don't really "need" one, but.. as I once built a tube version of this (far simpler) doing one in solid state appeals to me. Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
toroid cores?
25 Turns of #28 on a T50-2 is about 3.2 uH not 300 mH
23 Turns of #28 on a T50-2 is about 2.6 uH T50-2 has a AL of about 49 uH = (AL * TurnsSQR) / 10000 So... (49 * 625) / 10000 = 3.065 uH (25 turns) for 2 - 30 Mhz (49 * 529)/ 10000 = 2.592 uH (23 Turns) for 2-30Mhz -- ========================================= Radio Amateurs - Fill your junk box, from my junkbox! http://www.hamradparts.com 73 de KB9BVN ========================================= "Jamie" wrote in message ... Hi Newsgroup, Been trying to make a regen radio out of garbage. So far, I seem to have all the parts and it almost seems to work, however, I'm a bit confused about the inductance of toroid cores. I've tried to use one of those things from the back of a monitor (presumably to prevent RF interference) as one of the coils and another adjustable coil from another device, to no avail. It has no markings and it appears to be a ferrite device in the shape of a ring. Anyone know an easy way to figure out how many turns to get (presumably 300mh?) from one of these? Can I measure it with a ruler and some how get a formula for the number of turns / mH ? Are these really bad deviced to use? (the thought occurs I must admit, that if it was meant to BLOCK rf, using would be illogical) Here's the circuit I'm basing it on: http://www.tricountyi.net/~randerse/regen.htm If I inject a signal directly into the coil (in place of his amplified RF "front stage") I can pick it up, but no oscillation and lousy tuning. (comes in on pretty much 1/2 the dial) I'm assuming this has something to do with the tank circuit. (I have two air capacitors totalling around 360pf one from a console stereo, the other from some place I can't remember where..) He's got 25T and 23T specified for a T-50-2 coil. Closest research on these that I can find is that this should produce about 300mh (but I could be wrong! anyone know for sure what the mH is on that?) This seems to make sense from everything I've read so far, but.. I have no way to measure it. If I end up using an air core, would I keep the ratio of turns for the tickler and injection coil? (where he has 3 and 5 turns spec'd) ? It's my assumption that in these two smaller coils, it's a step up transformer so it'd be a matter of ratios, am I correct in this assumption? Every bit of the circuit should come from garbage (the MPF102's I had to buy, but thats it) Even the coil wire is from the transformer of a broken microwave, the LM386 chip used for audio (and some resistors) will come from an old modem and the pot is a 500k pot, (from a console) wired in parallel with a ~10k resistor to give a range between 0 - 10k ohms. The main point is to build it from garbage, I already have a radio and don't really "need" one, but.. as I once built a tube version of this (far simpler) doing one in solid state appeals to me. Jamie -- http://www.geniegate.com Custom web programming (rot13) User Management Solutions |
toroid cores?
I soldered fets with a max V gate to source of 10 volts with no prob. The trick is to wrap the leads together with some bare 30 guage and then after soldering remove the 30 guage. Use a grounded iron and set the pcb on a sheet of aluminum foil with 470k - 1 meg to ground the resistor is to save you if you touch something leaky and the foil at the same time - like a bad scope or something. Kirk KC7THL Hi, My luck (quite some time ago) with FETs was not nice either. Someone may have to correct my, yet the only way I think one can get away with fiddling with the things the way most people construct, might be to use zener diodes between the gate and source and drain. Once its all together and apparently functioning one probably could remove them then with less worry about then getting a little static jolt and ruining the junction. Tubes are a lot more forgiving. Sincerely, Gregory D. MELLOTT |
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