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Old July 14th 06, 05:41 PM posted to rec.radio.amateur.homebrew
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Default 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


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Old July 16th 06, 02:06 PM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 162
Default 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

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Old July 17th 06, 05:22 AM posted to rec.radio.amateur.homebrew
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Posts: 5
Default 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
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Old July 19th 06, 08:37 PM posted to rec.radio.amateur.homebrew
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Posts: 1
Default 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


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Old July 19th 06, 08:40 PM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 76
Default 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


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Old July 20th 06, 11:54 AM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 5
Default 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
  #17   Report Post  
Old July 20th 06, 12:07 PM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 162
Default 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

  #18   Report Post  
Old July 20th 06, 06:46 PM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 22
Default 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



  #19   Report Post  
Old July 20th 06, 07:03 PM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 22
Default 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



  #20   Report Post  
Old July 21st 06, 08:35 PM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 4
Default 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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