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