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

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

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

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

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

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

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

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?

--

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

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

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