Winding up a coil ?

[phil]

I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the winding?

Thanks.

 

[Dbowey]

Phil posted:
<< I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the wi >>

The instruction calls for the coil to be "close wound." The recommended wire
for this is enamel insulated. If that is what you are using, there is no need
to remove the insulation. If the insulation of your wire adds to the diameter
of the wire significantly, don't use it. The spacing between the *wire* of
adjacent turns will affect the reactance of the inductor, therefore, the
frequency.

Don

 

[Kevin Aylward]

Dbowey wrote:

Phil posted:
I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the wi

The instruction calls for the coil to be "close wound." The
recommended wire for this is enamel insulated. If that is what you
are using, there is no need to remove the insulation. If the
insulation of your wire adds to the diameter of the wire
significantly, don't use it. The spacing between the *wire* of
adjacent turns will affect the reactance of the inductor, therefore,
the frequency.

Yes, but a minor effect, in addition the spec says 8-10 turns, therefore
an accurate inductor has not been specified. The only reason for using
enamelled wire is to fit more turns in a smaller space. If you have lots
of space there, is no electrical reason not to use pretty much any bit
of wire, plastic insulated or not. There is just a convention mind set
that cores use enamelled wire, but for a few turns, space is usually
irrelevant so there is no need to follow that convention. In fact, I
have found multistranded wire to have slightly better performance.

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Dbowey]

Kevin posted:

Dbowey wrote:
Phil posted:
I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the wi

The instruction calls for the coil to be "close wound." The
recommended wire for this is enamel insulated. If that is what you
are using, there is no need to remove the insulation. If the
insulation of your wire adds to the diameter of the wire
significantly, don't use it. The spacing between the *wire* of
adjacent turns will affect the reactance of the inductor, therefore,
the frequency.

Yes, but a minor effect, in addition the spec says 8-10 turns, therefore
an accurate inductor has not been specified. The only reason for using
enamelled wire is to fit more turns in a smaller space. If you have lots
of space there, is no electrical reason not to use pretty much any bit
of wire, plastic insulated or not. There is just a convention mind set
that cores use enamelled wire, but for a few turns, space is usually
irrelevant so there is no need to follow that convention. In fact, I
have found multistranded wire to have slightly better performance.
---

1. How can you presume to know the effect of the insulation will be minor,
when you do not know the type and thickness of the insulation?

2. At VHF and above, the *conventional mindset* methods will always save you
a lot of trouble.

3. In what manner did you find multi-stranded wire to have better performance,
recalling that we are discussing 88 MHz and above?

Don

 

[Kevin Aylward]

Dbowey wrote:

Kevin posted:
Dbowey wrote:
Phil posted:
I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the wi

The instruction calls for the coil to be "close wound." The
recommended wire for this is enamel insulated. If that is what you
are using, there is no need to remove the insulation. If the
insulation of your wire adds to the diameter of the wire
significantly, don't use it. The spacing between the *wire* of
adjacent turns will affect the reactance of the inductor, therefore,
the frequency.

Yes, but a minor effect, in addition the spec says 8-10 turns,
therefore an accurate inductor has not been specified. The only
reason for using enamelled wire is to fit more turns in a smaller
space. If you have lots of space there, is no electrical reason not
to use pretty much any bit of wire, plastic insulated or not. There
is just a convention mind set that cores use enamelled wire, but for
a few turns, space is usually irrelevant so there is no need to
follow that convention. In fact, I have found multistranded wire to
have slightly better performance.
---
1. How can you presume to know the effect of the insulation will be
minor, when you do not know the type and thickness of the insulation?

Ahhmmm... Its trivial. I am reasonably familiar with typical hook up
wire and have made measurements on such wire that agree with the
elementary theory. That is, the approximate inductance of a coil doesn't
depend on wire thickness, or wire spacing. i.e. its N^2.uo.ur.A/L.
Arguable, the capacitance is less as there is more space. Only second
order effects modify this.

Again, packing wires close together is usually done for space reasons,
not performance reasons.

Just what do you expect the insulation to do to the inductance and self
capacitance?

2. At VHF and above, the *conventional mindset* methods will always
save you a lot of trouble.

Not always.

3. In what manner did you find multi-stranded wire to have better
performance, recalling that we are discussing 88 MHz and above?

It resulted in less phase shift error. I made quite a lot of
measurements on a transformer used to couple to the mains power in an
effort to measure power line impedance. Stranded wire gave better
results. Its that simple. You should actually try it sometime.

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Watson A.Name \"Watt Sun]

phil wrote:

I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the winding?

You don't have to remove the insulation, but the conductors will be
farther apart than if they were insulated with enamel. So the
inductance will be different. The instructions say to wind the turns
close wound, which means each turn touches the next. The heavy
insulation won't allow this.

Also, it says the coil should be 1/4" diameter, and a pencil is larger
than this. And also, the number of turns should be less than 8, more
like 6 or 4. I would start with 6, and then trim off some wire to bring
the frequency up. If you see herringbone pattern on the TV screen when
it's tuned to ch 5 or 6, then you know that the coil has too many turns,
and the signal is well below 88 MHz. With 8 turns, the freq might be as
low as ch 4.

> Thanks.

 

[Watson A.Name \"Watt Sun]

phil wrote:

I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the winding?

Thanks.

Two other things I forgot to mention. You should put a .01 uF, or .05
or .1 uF ceramic capacitor from +9V to ground. And you should keep
leads short, expecially around the RF oscillator Q2.

Also, increase R5 from 100 to 750 or until the voltage at the collector
of Q1 is about 4.5V.

 

[phil]

"Watson A.Name "Watt Sun - the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:c6rom2$6svso$1@hades.csu.net...

phil wrote:

I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the winding?

You don't have to remove the insulation, but the conductors will be
farther apart than if they were insulated with enamel. So the
inductance will be different. The instructions say to wind the turns
close wound, which means each turn touches the next. The heavy
insulation won't allow this.

Also, it says the coil should be 1/4" diameter, and a pencil is larger
than this. And also, the number of turns should be less than 8, more
like 6 or 4. I would start with 6, and then trim off some wire to bring
the frequency up. If you see herringbone pattern on the TV screen when
it's tuned to ch 5 or 6, then you know that the coil has too many turns,
and the signal is well below 88 MHz. With 8 turns, the freq might be as
low as ch 4.

What's is the connection between an fm oscillator and tv frequencies,
these start from 200mhz at the very least and go up to 800mhz?

Thanks.

 

[Watson A.Name \"Watt Sun]

phil wrote:

"Watson A.Name "Watt Sun - the Dark Remover"" <NOSPAM@dslextreme.com
wrote in message news:c6rom2$6svso$1@hades.csu.net...

phil wrote:

I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire. My g.22
wire is insulated, do I need do remove the insulation before
doing the winding?

You don't have to remove the insulation, but the conductors will be
farther apart than if they were insulated with enamel. So the
inductance will be different. The instructions say to wind the
turns close wound, which means each turn touches the next. The
heavy insulation won't allow this.

Also, it says the coil should be 1/4" diameter, and a pencil is
larger than this. And also, the number of turns should be less
than 8, more like 6 or 4. I would start with 6, and then trim off
some wire to bring the frequency up. If you see herringbone
pattern on the TV screen when it's tuned to ch 5 or 6, then you
know that the coil has too many turns, and the signal is well below
88 MHz. With 8 turns, the freq might be as low as ch 4.

What's is the connection between an fm oscillator and tv frequencies,
these start from 200mhz at the very least and go up to 800mhz?

Not in the U.S., they don't. Yet. The low VHF TV channels are from 54
to 88 MHz, so if you have too many turns or too much capacitance for the
tuning cap, it will oscillate down in the TV channels.

Sometimes they oscillate so nastily that the second harmonic is right in
the middle of a channel in the high VHF TV freqs from 174 to 216 MHz,
usually ch 7 or 8. The little transmitters can cause Ch 7 to become
all wavy and herringbone.

Did I tell you about the one wireless mic I had running that was making
a 9th harmonic that was causing the local cell phone site to drop off
customers on one channel? Yeah, really.

>>> Thanks.

 

[Rich Grise]

"Dbowey" <dbowey@aol.com> wrote in message
news:20040428214912.27697.00000217@mb-m17.aol.com...

Phil posted:
I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the wi

The instruction calls for the coil to be "close wound." The recommended
wire
for this is enamel insulated.

Can you please point out where it says enamel insulated? The page
I see when I click that link says "hookup wire," which is definitely
not enamel insulated. They're depending on the wire insulation (typically
plastic) to give the correct winding-to-winding spacing.

Good Luck!
Rich

 

[Rich Grise]

"Kevin Aylward" <kevindotaylwardEXTRACT@anasoft.co.uk> wrote in message
news:9Pckc.756$7n5.98@newsfe1-win...

Dbowey wrote:
1. How can you presume to know the effect of the insulation will be
minor, when you do not know the type and thickness of the insulation?

Ahhmmm... Its trivial. I am reasonably familiar with typical hook up
wire and have made measurements on such wire that agree with the
elementary theory. That is, the approximate inductance of a coil doesn't
depend on wire thickness, or wire spacing. i.e. its N^2.uo.ur.A/L.

Well, if N is number of turns, and L is length, then clearly they're
related, i.e. N/L = turns per length = 1/spacing.

It makes a difference.

Hope This Helps!
Rich

 

[cornytheclown]

"Watson A.Name \"Watt Sun - the Dark Remover\"" <NOSPAM@dslextreme.com> wrote in message news:<c6rom2$6svso$1@hades.csu.net>...

phil wrote:

I would like to build the fm transmitter kit from
http://www.uoguelph.ca/~antoon/circ/fmt1.htm

The instruction that L is 8-10 turns of a gauge 22 wire.
My g.22 wire is insulated, do I need do remove the
insulation before doing the winding?

You don't have to remove the insulation, but the conductors will be
farther apart than if they were insulated with enamel. So the
inductance will be different. The instructions say to wind the turns
close wound, which means each turn touches the next. The heavy
insulation won't allow this.

what the instructions say is to closely wind the coil using hookup
wire...Im sure the circuit designer knows that the insulation will
space the conductors apart......he or she has probably specified suing
the closely wound hookup wire because it will be easier for a beginner
to wind an inductor like that as opposed to spacing the windings a
wire diameter or so apart.

Its an fm transmitter with many cousins on the net and in books, most
circuits of this type call for a little spacing between turns and this
particular designer is using the insulation to make that
space....might sacrafice some Q but its a low power fm transmitter.

Also, it says the coil should be 1/4" diameter, and a pencil is larger
than this. And also, the number of turns should be less than 8, more
like 6 or 4. I would start with 6, and then trim off some wire to bring
the frequency up. If you see herringbone pattern on the TV screen when
it's tuned to ch 5 or 6, then you know that the coil has too many turns,
and the signal is well below 88 MHz. With 8 turns, the freq might be as
low as ch 4.

Thanks.