ART'S ANTENNA
 

On Jul 14, 2:29 pm, "amdx" wrote:
"Art Unwin" wrote in message

...

On Jul 14, 10:51 am, "Frank" wrote:
Hi Art
The details for the variometer would be of help if you could
oblige thank you.

Derek

The following explains the construction:

http://www.g0mrf.freeserve.co.uk/variometer.htm

Variometers can be very lossy variable inductors. For proper
matching 2 elements are required.

Oh, that little, that's thing is for girls, seehttp://w5jgv.com/variometer/variometer.htm
Mike :-)

That one is at least four times the coil turns needed. The previous
one was at least two times the number of coils need.
And if the wire length used was 1100 feet or so the latter also is
much more than required and can be divided by two again.
The idea is not to put a 1000 feet of wire on the variometer or to use
the radiator beyond the HF bands!

ART'S ANTENNA
 

Frank wrote:

The following explains the construction:

http://www.g0mrf.freeserve.co.uk/variometer.htm

Variometers can be very lossy variable inductors. For proper
matching 2 elements are required.

A general rule of thumb for electrically small antennas is:
small-broadband-efficient, pick any two. One of the common features of
many small antennas is some lossy component or components which make the
bandwidth acceptable. Of course, this also means lowered efficiency,
often to an extreme extent. But most amateurs are able to measure SWR
and almost none are able to measure efficiency, so the loss fools a lot
of people into thinking the small antenna is performing well. I suspect
the variometer is the "secret ingredient" in this case, and that its
chief function is to provide loss. People duplicating the antenna might
try substituting a non-inductive resistor as a simpler way to achieve
the same result.

This isn't to say that a small inefficient antenna "doesn't work". I've
personally worked over 30 countries with a watt and a half on 40 meters
using simple antennas, and many, many people have done a great deal
better with much lower power. So you can still work a lot of stations
with a 100 watt rig and 1% efficient antenna.

Roy Lewallen, W7EL

ART'S ANTENNA
 

On Jul 14, 10:51 am, "Frank" wrote:
Hi Art
The details for the variometer would be of help if you could
oblige thank you.

Derek

The following explains the construction:

http://www.g0mrf.freeserve.co.uk/variometer.htm

Variometers can be very lossy variable inductors. For proper
matching 2 elements are required.

73,

Frank

2 elements required? What does that mean?

ART'S ANTENNA
 

Art Unwin wrote:

...
2 elements required? What does that mean?

Who knows absolutely?

But, most likely, he means a dipole.

On a full wave monopole with no counterpoise and choking off the outer
braid ... I guess you have "one element" as opposed to "2 elements" (for
example: monopole-with-counterpoise/dipole 1/4 wave, 1/2 wave.)

But then, I am guessing. scratches head

Regards,
JS

ART'S ANTENNA
 

2 elements required? What does that mean?

In most cases an inductor, and capacitor, is required to match
a complex impedance, as follows:

Shunt C, Series L;
Shunt L, Series C;
Series L, Shunt C, or;
Series C, Shunt L.

Only rarely can a single component provide a match.

73,

Frank

ART'S ANTENNA
 

On Jul 14, 7:23 pm, "Frank" wrote:
2 elements required? What does that mean?

In most cases an inductor, and capacitor, is required to match
a complex impedance, as follows:

Shunt C, Series L;
Shunt L, Series C;
Series L, Shunt C, or;
Series C, Shunt L.

Only rarely can a single component provide a match.

73,

Frank

Has not a variometer 2 elements?

ART'S ANTENNA
 

Art Unwin wrote:

...
2 elements required? What does that mean?

There ya' go ... his response.

It appears, what he was saying was/is, you cannot obtain maximum
transfer of power to the antenna with the variometer alone--you must use
a pi/LC/etc. (a capacitance in conjunction with an inductance) ...

I re-read his post, that meaning was implied well--but I could only see
it with hindsight.

JS

ART'S ANTENNA
 

In most cases an inductor, and capacitor, is required to match
a complex impedance, as follows:

Shunt C, Series L;
Shunt L, Series C;
Series L, Shunt C, or;
Series C, Shunt L.

Only rarely can a single component provide a match.

73,

Frank

Has not a variometer 2 elements?

No. A variometer is simply a variable inductor.

I should also have added to the above:
Series L, Shunt L etc. etc.......

Frank

ART'S ANTENNA
 

On Jul 14, 8:36 pm, "Frank" wrote:
In most cases an inductor, and capacitor, is required to match
a complex impedance, as follows:

Shunt C, Series L;
Shunt L, Series C;
Series L, Shunt C, or;
Series C, Shunt L.

Only rarely can a single component provide a match.

73,

Frank

Has not a variometer 2 elements?

No. A variometer is simply a variable inductor.

I should also have added to the above:
Series L, Shunt L etc. etc.......

Frank

Then what I can do is to split the circuit in half of a varometer
and connect one in series with the positive and one in series to the
negative
so I have equal turns added or subtracted of opposite wound and
controlled by the single motor.
Sounds good

ART'S ANTENNA
 

Frank wrote:
2 elements required? What does that mean?

In most cases an inductor, and capacitor, is required to match
a complex impedance, as follows:

Shunt C, Series L;
Shunt L, Series C;
Series L, Shunt C, or;
Series C, Shunt L.

Only rarely can a single component provide a match.

Other combinations can be used, for example, adjusting a transmission
line stub length and position, or a transformer in conjunction with a
reactance. The point is that an impedance has two values, commonly
expressed as R and X or as a magnitude and phase angle, so to achieve a
specific impedance requires two "degrees of freedom" -- that is, two
things which you can adjust and which, in simple terms, don't adjust
exactly the same thing. With only one adjustable element, you can get a
specific R, say, or X, but not both.

Roy Lewallen, W7EL