Vfo coil design query
Roger A. McCarty
Is there any advantage in the size of wire chosen in winding the L component
on a ferrite core? That is, is there a stability difference when using
smaller or larger gauge wire?
Also, Row Lewellyn suggests "annealing" the coil by boiling it in water for
a few minutes. What does this accomplish?
Thanks
Roger KD6CC
Leon Heller
In article <6gqulj$2...@chile.earthlink.net>, "Roger A. McCarty"
<rmcc...@earthlink.net> writes
>Is there any advantage in the size of wire chosen in winding the L component
>on a ferrite core? That is, is there a stability difference when using
>smaller or larger gauge wire?
You get more Q with thicker wire.
Leon
--
Leon Heller: le...@lfheller.demon.co.uk http://www.lfheller.demon.co.uk
Amateur Radio Callsign G1HSM Tel: +44 (0) 118 947 1424
See http://www.lfheller.demon.co.uk/dds.htm for details of my AD9850
DDS system. See " "/diy_dsp.htm for a simple DIY DSP ADSP-2104 system.
JohnsonHE
>
>You get more Q with thicker wire.
>
>Leon
>--
Not always, and particularly, not always with a toroid. Reference Optimum wire
size for RF coils, by W7XC, QEX August 1987.
W4ZCB
Roy Lewallen
In article <6gqulj$2...@chile.earthlink.net>, "Roger A. McCarty" <rmcc...@earthlink.net> wrote:
>Is there any advantage in the size of wire chosen in winding the L component
>on a ferrite core? That is, is there a stability difference when using
>smaller or larger gauge wire?
>
>a few minutes. What does this accomplish?
>
>Thanks
>
>Roger KD6CC
There's very little difference in using different wire sizes, except that
the wire should be small enough to conform reasonably well to the core
shape, and shouldn't be so large as to require more than a single layer.
(See "Choosing Wire Size for Toroidal Inductors", Technical Correspondence,
QST, April 1983, p. 39.
I got the "annealing" idea from Wes Hayward, W7ZOI, for treating VFO tank
inductors. This process reduces the temperature coefficient of the
inductor. It's speculated that the improvement is due to relief of
stresses, but I don't believe anyone knows for sure. Both Wes and I have
confirmed that it does indeed work. It isn't useful unless you require
extreme temperature stability, as in a VFO tank inductor.
Roy Lewallen, W7EL
Roger A. McCarty
Thank you, Roy. And sorry 'bout butchering your name! :-}
The question came from my recent build of a Sieler VFO (Solid State Design
pg..35) for 80 meters. The wire I used is larger than an associate
recommended (hair like) and I thought perhaps the significant change
temperature had on the circuit was due to the larger wire. Quite literally
walking into the room would cause a sudden but slow drift. Blowing on the
inductor has an extreme effect. I am quite sure it is only the inductor
because isolating and moderately heating/cooling the capacitors has a
reasonable and expected effect.
I built the "Optimized QRP" rig a number of years ago, prior to knowing what
I was doing :-}, and followed your suggestion precisely in the preparation
of the toroid. Seemed quite stable as I remember. Perhaps I'll give it
another try with this rig.
73
Roger KD6CC
Roy Lewallen wrote in message <61dY.313$EI4.3...@news2.teleport.com>...
JohnsonHE
>
>I got the "annealing" idea from Wes Hayward, W7ZOI, for treating VFO tank
>inductors. This process reduces the temperature coefficient of the
>inductor. It's speculated that the improvement is due to relief of
>stresses, but I don't believe anyone knows for sure. Both Wes and I have
>confirmed that it does indeed work. It isn't useful unless you require
>extreme temperature stability, as in a VFO tank inductor.
>
>Roy Lewallen, W7EL
I don't believe that hot water is hot enough to take the hard out of hard drawn
or "work hardened" copper wire, perhaps it is. I like to just take my variac
and crank enough current into the wire after it's formed to get it hot (usually
look for 400-500 degrees on the thermocouple if everything else will stand it)
and then let it cool. Hard drawn copper wire only has 60 percent the
conductivity of soft drawn wire.
W4ZCB
JohnsonHE
>
>There's very little difference in using different wire sizes, except that
>the wire should be small enough to conform reasonably well to the core
>shape, and shouldn't be so large as to require more than a single layer.
>(See "Choosing Wire Size for Toroidal Inductors", Technical Correspondence,
>QST, April 1983, p. 39.
If you actually measure the Q of the completed toroid, you can get an
appreciable increase in using a wire diameter tha allows a bit of space between
turns at the inside face of the toroid, thereby reducing the turn to turn
capacity and the "proximity effect", (non-uniform current distribution in the
wire). A wire size selected to "fill" the space available, does not yield the
highest Q. (I've heard of more is less, but in this case, less is more).
W4ZCB
Zack Lau
Leon Heller wrote:
>You get more Q with thicker wire.
I think this depends the ratio of core to copper loss.
Toroids with a Qs over 400 seem to be affected more by wire size
than inductors with twice as much loss.--Zack Lau W1VT
Roy Lewallen
I don't think anyone is using hard drawn wire for making coils, and don't
think that the winding process work hardens the wire. But your method of
heating should accomplish the same thing as the boiling process.
Roy Lewallen, W7EL
Roy Lewallen
Here are the measurements I made and included in the Technical
Correspondence piece I referenced earlier. All coils were 22 turns on
T-50-6 cores, measured at 14 MHz.
Wire Size Meas. L Meas. Q
(AWG) (uH)
21 2.10 252
22 2.17 237
24 2.17 250
26 2.07 248
28 2.15 220
30 2.13 196
32 2.28 182
from which I concluded "Within the accuracy of the test fixture, and
expected core-to-core variation, the inductors wound with wire nos. 21
through 26 are the same. There is a definite drop in Q for inductors wound
with no. 28 and smaller wire, but even this drop in Q won't be noticeable
unless the inductor is used in a critical application, such as a VFO tank
or a high-Q filter."
It would be helpful if you would post your measurements, to help determine
under what conditions the wire diameter is and isn't important.
Roy Lewallen, W7EL
Roger A. McCarty
Thank you to all who contributed to the discussion. The information and data
gathered will be most useful in future projects.
73
Roger KD6CC
Joanne Dow
JohnsonHE wrote:
> >
> >I got the "annealing" idea from Wes Hayward, W7ZOI, for treating VFO tank
> >inductors. This process reduces the temperature coefficient of the
> >inductor. It's speculated that the improvement is due to relief of
> >stresses, but I don't believe anyone knows for sure. Both Wes and I have
> >confirmed that it does indeed work. It isn't useful unless you require
> >extreme temperature stability, as in a VFO tank inductor.
> >
> >Roy Lewallen, W7EL
>
> I don't believe that hot water is hot enough to take the hard out of hard drawn
> or "work hardened" copper wire, perhaps it is. I like to just take my variac
> and crank enough current into the wire after it's formed to get it hot (usually
> look for 400-500 degrees on the thermocouple if everything else will stand it)
> and then let it cool. Hard drawn copper wire only has 60 percent the
> conductivity of soft drawn wire.
And watch your core characteristics go to Floobistan.
{O.O} Joanne Dow, jd...@bix.com
David Stockton
JohnsonHE wrote:
>
>
> I don't believe that hot water is hot enough to take the hard out of hard drawn
> or "work hardened" copper wire, perhaps it is. I like to just take my variac
> and crank enough current into the wire after it's formed to get it hot (usually
> look for 400-500 degrees on the thermocouple if everything else will stand it)
> and then let it cool. Hard drawn copper wire only has 60 percent the
> conductivity of soft drawn wire.
I don't think that it's the wire that's being affected. I believe
it's the core. With a dust iron core, it's easy to look up the curie
temperature of the alloy used, but for very low tempco effects at room
temperatures, the binding material is most likely the chief culprit, and
could easily be affected by a 100 celsius dunking.
Ferrite materials have some interesting juvenile ageing effects, too.
Look up "Disaccomodation" in one of the standard texts like "Soft
Ferrites" by Snelling.
Cheers
David GM4ZNX
Toroids
increasing the wire gauges increases the Q by a small amoun t but it is
significant when competing with the best in the world to nit pick every bit of
Q out of an inductor. Annealing is to soften metal to take out the memory (
spring )in a coil when heating it the metal tries to bend back to its previos
position. the overal temp drift is in the ppm/c of the metal of the wire and
MORE SO the ferrite core. I don't suggest doing that because you can de Q the
core or crack it. Anneal the wire before winding it. or use silver wire which
is very soft.
visit this web site for toroid , ferrite and iron powder cores
http://members.aol.com/Toroids/johnindx.htm
or reply to Tor...@aol.com
Toroids
bogus answer about the wire not helping Q on a toroid
Toroids
not so! I build filters on a daily basis dc to 40 GHz and am competing with and
against the best in the world. it has nothing to do with the ratio. In an RLC
circuit , if the loss of the inductor is the lower Q of the LC resonator than
the cap, the wire always helps the loss providing that you are not using the
wrong core material for the frequency range, in which case the core acts more
as an absorber and the Q is driven to low to see a difference. The lower Q
inductors benefit the most and also the lower the perm of the core. there are
many other factors that are non published which can increase the Q but they
must remain proprietary for obvious reasons
John
Tor...@aol.com
Toroids
yes people do know for sure. You are right the stress relief is exactly why.
The temperature coefficient if a metal does not change by annealing but it does
soften the metal and helpa relieve the memory or springyness that willl causes
a metal to try and bend back to its previos position when shocked with hot or
cold sudden changes.iDesighn , temperature test and tune microwave filters dc
to 40 GHz on a daily basis and reasearch metals and ceramics.I have written
software to calculate expanding and contracting combinations of metals
over temp extremes -55 to+ 25 degrees celcius for cavity filters and ceramics.
You may find my toroid program that i have in the market usefull
reply to Tor...@aol.com or down load a demo
http://members.aol.com/Toroids/johnindx.htm