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