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