On 9 Oct 2003 23:39:07 -0700, (OK1SIP) wrote:
Variometers are often used for tuning antennas at 136 kHz. See
http://www.sweb.cz/ok1fig/Small_vario.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_02.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_03.jpg or
http://www.g0mrf.freeserve.co.uk/variometer.htm .

BR from Ivan

Hi Ivan,

Those are some great variometers.

73's
Richard Clark, KB7QHC

Richard.
You have no need to be sorry!
\You are trying to help me and
I appreciate that.
My problem started when I moved
away from a homebrew coil on a circuit
which was coupled to a rod ( distributed inductance)
The coupled rod when moved allowed for
an ideal matching setup
as it could be made into a perfect match
for top band use.( the rod was the driven element)
When I substituted a variometer for fine
tuning everything went to pot!
(That is why they call mesh circuits 'complex' )
Thus the questions regarding variometers
and the markings. With the new band in
the U.K. being used I suspect we are going
to hear a lot more about this instrument
and I can then reintroduce it on my antenna
Best regards
Art




(Richard Harrison) wrote in message ...
Art Unwin, KB9MZ wrote:
"Could you share with me a method of approximating the total inductance
together with its variance values?"

The design of shortwave coils is a complicated process. Skin effect
causes most loss, and single-strand wire wound as a single-layer coil is
usually best. According to Terman, the highest Q is usually, for a given
sized coil, gotten by a winding length somewhat less than the diameter
of the coil. Terman refers to an article in "Wireless Eng.", vol. 26,
page 179, June 1949 by G.W.O. Howe.

My big help with coils comes from the ARRL "L/C/F Calcululator", a
specialized slide-rule. My "Model A" has a price of $2.00 printed on it.

Tom Bruhns has done a lot of work with coils and knows much more about
them than I do. Maybe he will offer some help.

Reg has studied the pertinent factors and used them for some of his
marvelous programs, so he can be a big help.

Sorry I am not qualified to be much help. My method has been "cut and
try".

I was reading an excellent article from a 1920 QST as reprinted in
January 1966, by E.H. Armstrong about his Signal Corps research in WW-1.
He noted that his IF transformers benefitted from many turns of fine
wire which reduced capacitance and added enough resistance to dampen
oscillation tendencies. Armstrong was using "Type 5" triodes in his IF
amplifier of 100 KHz. I am sorry that I am so out of date.

Best regards, Richard Harrison, KB5WZI

What a great posting!
The input and work has not gone unnoticed
and I am sure that all on the net appreciate
your presence. I need time to digest it as I
am now in a state of confusion regarding the subject
and its applicability to my particular project.
Many, many thanks for your effort
Art





(OK1SIP) wrote in message . com...
Hi Art,
the connection "all in series" is the proper one, not "particular".
Usually there are four parts of winding: one half of fixed coil, two
halves of moving coil and another half of fixed coil. Let's mark the
fixed coil inductance L1 and the moving coil L2. The construction is
made so that L1=L2 and magnetic coupling is as tight as possible. The
mutual inductance when both coils have the same axis is therefore
approximately M=L1=L2.
If the moving coil is turned so that the magnetic fields add, the
total inductance is (nearly) L = L1+L2+2M = 4*L1.
If the moving coil is turned so it is perpendicular to the fixed one
and the magnetic fields do not influence the other coil, the mutual
inductance is zero and the total inductance is L = L1+L2 = 2*L1.
If the moving coil is turned so that the magnetic fields subtract, the
total inductance is (nearly) L = L1+L2-2M = 0.
When you added some turns, you destroyed the construction symmetry.
Measuring the total inductance at various coil positions within 0..180
deg and at the working frequecy is the best you can do.

Variometers are often used for tuning antennas at 136 kHz. See
http://www.sweb.cz/ok1fig/Small_vario.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_02.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_03.jpg or
http://www.g0mrf.freeserve.co.uk/variometer.htm .

BR from Ivan


(Art Unwin KB9MZ) wrote in message om...
Richard,
On reflection I now see that how a variometer is
connected up can make a big difference.
In my particular case all coils are connected in
series such that the current is constant thru out.
An alternative way of connecting a variometer I suppose
is to supply a different current or placing the revolvable
inductance as part of another separate circuit whereas the
COUPLING action alone will provide the variances you speak of.
As for adding inductances in series, as stated in my earlier
reply, is a lot different such that I now believe my
original analysis is correct.( In other words I have just
increased the number of turns by sliding the inductances
together to make one inductor leaving the third inductor
which is revolveable seen as an inductance with reversable
turns or flux pattern.)
As you probably can now see I am totally confused,
especially since this arrangement is then coupled
to another separate circuit which is where I suspect the
+ or - 'M' variation comes into play comes into play.
Regards
Art

Before this thread bites the dust
Can anyone point out the meanings of the markings
on my commercial variometer?
The markings are

3600-5000KC

Thanks in advance
Art





(Art Unwin KB9MZ) wrote in message om...
What a great posting!
The input and work has not gone unnoticed
and I am sure that all on the net appreciate
your presence. I need time to digest it as I
am now in a state of confusion regarding the subject
and its applicability to my particular project.
Many, many thanks for your effort
Art





(OK1SIP) wrote in message . com...
Hi Art,
the connection "all in series" is the proper one, not "particular".
Usually there are four parts of winding: one half of fixed coil, two
halves of moving coil and another half of fixed coil. Let's mark the
fixed coil inductance L1 and the moving coil L2. The construction is
made so that L1=L2 and magnetic coupling is as tight as possible. The
mutual inductance when both coils have the same axis is therefore
approximately M=L1=L2.
If the moving coil is turned so that the magnetic fields add, the
total inductance is (nearly) L = L1+L2+2M = 4*L1.
If the moving coil is turned so it is perpendicular to the fixed one
and the magnetic fields do not influence the other coil, the mutual
inductance is zero and the total inductance is L = L1+L2 = 2*L1.
If the moving coil is turned so that the magnetic fields subtract, the
total inductance is (nearly) L = L1+L2-2M = 0.
When you added some turns, you destroyed the construction symmetry.
Measuring the total inductance at various coil positions within 0..180
deg and at the working frequecy is the best you can do.

Variometers are often used for tuning antennas at 136 kHz. See
http://www.sweb.cz/ok1fig/Small_vario.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_02.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_03.jpg or
http://www.g0mrf.freeserve.co.uk/variometer.htm .

BR from Ivan


(Art Unwin KB9MZ) wrote in message om...
Richard,
On reflection I now see that how a variometer is
connected up can make a big difference.
In my particular case all coils are connected in
series such that the current is constant thru out.
An alternative way of connecting a variometer I suppose
is to supply a different current or placing the revolvable
inductance as part of another separate circuit whereas the
COUPLING action alone will provide the variances you speak of.
As for adding inductances in series, as stated in my earlier
reply, is a lot different such that I now believe my
original analysis is correct.( In other words I have just
increased the number of turns by sliding the inductances
together to make one inductor leaving the third inductor
which is revolveable seen as an inductance with reversable
turns or flux pattern.)
As you probably can now see I am totally confused,
especially since this arrangement is then coupled
to another separate circuit which is where I suspect the
+ or - 'M' variation comes into play comes into play.
Regards
Art

I would assume it means that the tuning range was 3.6 MHz to 5.0 MHz
(3600 kHz or kc to 5000 kHz)

Mark

--
On 11 Oct 2003 17:10:20 -0700, (Art Unwin KB9MZ)
wrote:

Before this thread bites the dust
Can anyone point out the meanings of the markings
on my commercial variometer?
The markings are

3600-5000KC

Thanks in advance
Art





(Art Unwin KB9MZ) wrote in message om...
What a great posting!
The input and work has not gone unnoticed
and I am sure that all on the net appreciate
your presence. I need time to digest it as I
am now in a state of confusion regarding the subject
and its applicability to my particular project.
Many, many thanks for your effort
Art





(OK1SIP) wrote in message . com...
Hi Art,
the connection "all in series" is the proper one, not "particular".
Usually there are four parts of winding: one half of fixed coil, two
halves of moving coil and another half of fixed coil. Let's mark the
fixed coil inductance L1 and the moving coil L2. The construction is
made so that L1=L2 and magnetic coupling is as tight as possible. The
mutual inductance when both coils have the same axis is therefore
approximately M=L1=L2.
If the moving coil is turned so that the magnetic fields add, the
total inductance is (nearly) L = L1+L2+2M = 4*L1.
If the moving coil is turned so it is perpendicular to the fixed one
and the magnetic fields do not influence the other coil, the mutual
inductance is zero and the total inductance is L = L1+L2 = 2*L1.
If the moving coil is turned so that the magnetic fields subtract, the
total inductance is (nearly) L = L1+L2-2M = 0.
When you added some turns, you destroyed the construction symmetry.
Measuring the total inductance at various coil positions within 0..180
deg and at the working frequecy is the best you can do.

Variometers are often used for tuning antennas at 136 kHz. See
http://www.sweb.cz/ok1fig/Small_vario.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_02.jpg ,
http://www.sweb.cz/ok1fig/Big_vario_03.jpg or
http://www.g0mrf.freeserve.co.uk/variometer.htm .

BR from Ivan


(Art Unwin KB9MZ) wrote in message om...
Richard,
On reflection I now see that how a variometer is
connected up can make a big difference.
In my particular case all coils are connected in
series such that the current is constant thru out.
An alternative way of connecting a variometer I suppose
is to supply a different current or placing the revolvable
inductance as part of another separate circuit whereas the
COUPLING action alone will provide the variances you speak of.
As for adding inductances in series, as stated in my earlier
reply, is a lot different such that I now believe my
original analysis is correct.( In other words I have just
increased the number of turns by sliding the inductances
together to make one inductor leaving the third inductor
which is revolveable seen as an inductance with reversable
turns or flux pattern.)
As you probably can now see I am totally confused,
especially since this arrangement is then coupled
to another separate circuit which is where I suspect the
+ or - 'M' variation comes into play comes into play.
Regards
Art

Art Unwin, KB9MZ wrote:
"The markings are 3600 - 5000 KC."

"KC" may date the variometer back several decades or more.

Inductance has units of flux linkages per amp.

A single-layer solenoid has an inductance in microhenries of:
L = (n squared) (d) (form factor)
n = number of turns
d = diameter of the coil
form factor = complicated constant that depends on the length to
diameter ratio

See Terman`s 1955 edition, page 11 for the inductance story.

Inductance does not have a frequency term in its formula, but inductive
reactance is proportional to frrequency.

I guess that the variometer`s frequency markings are related to Q.
Resistance rises as the sq rt of frequency due to skin effect. Q will be
inversely proportional to r-f resistance in a coil.

As Reg Edwards has already said, a variometer`s Q is likely very poor
when set for low inductance. Q is XL/R.

Changing the variometer`s inductance setting has almost no effect on its
resistance. Its Q will be low enough at maximum inductance setting on a
shortwave variometer. Lower XL and don`t change the R. The effect on Q
is obvious.

I suspect the variometer was optimized for Q in the 3600 - 5000 MHz
range.

Best regards, Richard Harrison, KB5WZI

Art Unwin, KB9MZ wrote:
"The markings are 3600 - 5000 KC."




It was used in a radio or transmitter operating in that range. (German WW II
SK10?)

Yuri

On 12 Oct 2003 03:24:10 GMT, oSaddam (Yuri Blanarovich)
wrote:

Art Unwin, KB9MZ wrote:
"The markings are 3600 - 5000 KC."
It was used in a radio or transmitter operating in that range. (German WW II
SK10?)

Yuri

Hi Yuri,

More probable is Marine DF.

73's
Richard Clark, KB7QHC

Richard Clark wrote in message . ..
On 12 Oct 2003 03:24:10 GMT, oSaddam (Yuri Blanarovich)
wrote:

Art Unwin, KB9MZ wrote:
"The markings are 3600 - 5000 KC."
It was used in a radio or transmitter operating in that range. (German WW II
SK10?)

Yuri

Hi Yuri,

More probable is Marine DF.

73's
Richard Clark, KB7QHC

After digging into this subject so that I fully understand it I found
that this particular antenna did not work as it should have done. This
'dummy' assumed that I could obtain any Q that I wanted, however
actual inductor was very inefficient for top band use ( very
broadbanded because of losses.)
I went from 4 inch diameter inductance windings to
a 12 inch o/a diameter with 0.6, O.D. copper tubing for a total length
for the inductor of 35 inches. My intention is to now flatten the
copper tubing so the edges to provide minimum interwinding
capacitance.
However I do want the maximum Q available so the antenna is narrow
banded and inductance change is made by lessening the inductance
length for moving around the band.( or possibly the insertion of a
brass rod)

What other options do I have for increasing Q other than silver
plating of the copper?
I opted away from LITZ wire as I figured that top band was too
high a frequency to benefit from its properties.
Any comments or discussion of the subject would be very apreciated
Best regards
Art

On 19 Oct 2003 16:49:23 -0700, (Art Unwin KB9MZ)
wrote:

What other options do I have for increasing Q other than silver
plating of the copper?

Hi Art,

Make it as small as possible, with as large as possible conductors.
Look at any of the small, tunable, loop antennas on the market.

As a bonus, you also get to participate in the eternal debate about
the voltage found at the ends of a dipole when your own construction
begins arcing big time.

73's
Richard Clark, KB7QHC