Receiving Loop Antenna Question
 

In message , Allodoxaphobia
writes
On Fri, 23 Jan 2009 13:57:40 +0000, dave wrote:
Ian Jackson wrote:

What about ribbon cable? I've got a fair length of ribbon cable
(something like 25 wires - the sort used in PCs to connect hard drives
and the like) put away for a rainy-day loop antenna project. While I
could make one large loop using all 25 wires for the really low
frequencies, I'll almost certainly cut it up and make several smaller
loops with fewer wires for the higher frequencies.

Stick with a single wire and relatively few loops. More wire won't make
the loop bigger, just harder to tune.

I don't think he meant to connect all those wires in parallel.
But, it would be a little tedious to connect each wire at one end to its
neighbor at the other end (of the loop), and _not_ create an ugly bird's
nest at the 'joint'.

I think that you underestimate my constructional abilities!
I'm not sure how many turns would be needed. 4, 5 or 6 at the most
(depending on frequency)? I'd certainly study the available information
before I started. Of course, before I started, any superfluous wires
would be stripped from the ribbon - it's just that the ribbon I've got
has a lot wires.

I really can't see any problem with cutting the ribbon, and then
re-joining it with the end of each wire being connected to its neighbour
This technique MUST have been used before by someone.
--
Ian

Receiving Loop Antenna Question
 

In message , Jerry
writes

"Allodoxaphobia" wrote in message
...
On Fri, 23 Jan 2009 13:57:40 +0000, dave wrote:
Ian Jackson wrote:

What about ribbon cable? I've got a fair length of ribbon cable
(something like 25 wires - the sort used in PCs to connect hard drives
and the like) put away for a rainy-day loop antenna project. While I
could make one large loop using all 25 wires for the really low
frequencies, I'll almost certainly cut it up and make several smaller
loops with fewer wires for the higher frequencies.

Stick with a single wire and relatively few loops. More wire won't make
the loop bigger, just harder to tune.

I don't think he meant to connect all those wires in parallel.
But, it would be a little tedious to connect each wire at one end to its
neighbor at the other end (of the loop), and _not_ create an ugly bird's
nest at the 'joint'.

Jonesy


Hi Jonesy

For what Its Worth, I tried making a big AM reception loop using some big
ribbon cable, and it didnt work. The cable was/is color coded so it was
easy to connect the ends so the input to output is a series connection of
the wires. The antenna didnt work. I assummed it was due to excessive
'distributed capacity' between windings. I had no interest in researching
the reason for ribbon cable use for AM loop antennas. Besides, it got Very
difficult to assemble the loop onto the mounting frame and have it look
presentable.

Your findings are noted. I did wonder about the effects of distributed
capacity between the windings. It looks like it's back to the drawing
board!

" Stick with a single wire and relatively few loops. More wire won't
make
the loop bigger, just harder to tune."

Jerry KD6JDJ
--
Ian

Receiving Loop Antenna Question
 

On Jan 23, 8:45*am, Allodoxaphobia wrote:
On Fri, 23 Jan 2009 13:57:40 +0000, dave wrote:
Ian Jackson wrote:

What about ribbon cable? I've got a fair length of ribbon cable
(something like 25 wires - the sort used in PCs to connect hard drives
and the like) put away for a rainy-day loop antenna project. While I
could make one large loop using all 25 wires for the really low
frequencies, I'll almost certainly cut it up and make several smaller
loops with fewer wires for the higher frequencies.

Stick with a single wire and relatively few loops. More wire won't make
the loop bigger, just harder to tune.

I don't think he meant to connect all those wires in parallel.
But, it would be a little tedious to connect each wire at one end to its
neighbor at the other end (of the loop), and _not_ create an ugly bird's
nest at the 'joint'.

Jonesy

Yep, it's a continuous single wire. If you used ribbon cable, you
would have to put a cut, and the jumper to jump over to the next
wire on each turn.. Would be a pain.
You just take a single length of wire and thread it around
through the holes until you have the number of turns you need.
You are moving over a row of holes on each turn.
The main thing to consider is you end up building the loop
and deciding the proper number of turns around the
capacitor you have, not the other way around.
A double 365pf cap "730 pf total if jumped together" will let
you be able to tune the whole AM-BC band with most loops.
My 44 inch per side diamond loop for MW has five turns.
My 16 inch diameter circle loop for MW uses 12 turns.
Both are using basically the same cap values.
I also use a single turn coupling loop that is inside and
slightly smaller than the main loop. But it does not effect
tuning, and it's size and spacing from the main loop is fairly
uncritical. The cap is in parallel with the main loop winding.
If you use a portable with a built in loop stick antenna,
you can just couple the radio to the loop and it will
work. But all my radios require a feed line to the antenna.

Receiving Loop Antenna Question
 

wrote:
My 16 inch diameter circle loop for MW uses 12 turns.

I know multiple loop antennas are lossy for transmitting.
Are they adequate for receiving because of the AGC dynamic
range in the receiver?
--
73, Cecil http://www.w5dxp.com

Receiving Loop Antenna Question
 

On Jan 25, 3:51*am, wrote:
On Jan 23, 8:45*am, Allodoxaphobia wrote:



On Fri, 23 Jan 2009 13:57:40 +0000, dave wrote:
Ian Jackson wrote:

What about ribbon cable? I've got a fair length of ribbon cable
(something like 25 wires - the sort used in PCs to connect hard drives
and the like) put away for a rainy-day loop antenna project. While I
could make one large loop using all 25 wires for the really low
frequencies, I'll almost certainly cut it up and make several smaller
loops with fewer wires for the higher frequencies.

Stick with a single wire and relatively few loops. More wire won't make
the loop bigger, just harder to tune.

I don't think he meant to connect all those wires in parallel.
But, it would be a little tedious to connect each wire at one end to its
neighbor at the other end (of the loop), and _not_ create an ugly bird's
nest at the 'joint'.

Jonesy

Yep, it's a continuous single wire. If you used ribbon cable, you
would have to put a cut, and the jumper to jump over to the next
wire on each turn.. Would be a pain.
You just take a single length of wire and thread it around
through the holes until you have the number of turns you need.
You are moving over a row of holes on each turn.
The main thing to consider is you end up building the loop
and deciding the proper number of turns around the
capacitor you have, not the other way around.
A double 365pf cap "730 pf total if jumped together" will let
you be able to tune the whole AM-BC band with most loops.
My 44 inch per side diamond loop for MW has five turns.
My 16 inch diameter circle loop for MW uses 12 turns.
Both are using basically the same cap values.
I also use a single turn coupling loop that is inside and
slightly smaller than the main loop. But it does not effect
tuning, and it's size and spacing from the main loop is fairly
uncritical. The cap is in parallel with the main loop winding.
If you use a portable with a built in loop stick antenna,
you can just couple the radio to the loop and it will
work. But all my radios require a feed line to the antenna.

I would not be so quick to dismiss the ribbon wire on the basis of
capacitance build up ! If you start from the middle of one end by
joining
the two center wires together and from then on joining the end to end
wires
moving outwards what you have then done is to cancel not only the
capacitance build up but also the inductance build up.
You can then unfasten the first step on the center winding and feed it
from that point
i.e. center fed
Art

Receiving Loop Antenna Question
 

"Art Unwin" wrote in message
...
On Jan 25, 3:51 am, wrote:
On Jan 23, 8:45 am, Allodoxaphobia wrote:



On Fri, 23 Jan 2009 13:57:40 +0000, dave wrote:
Ian Jackson wrote:

What about ribbon cable? I've got a fair length of ribbon cable
(something like 25 wires - the sort used in PCs to connect hard
drives
and the like) put away for a rainy-day loop antenna project. While I
could make one large loop using all 25 wires for the really low
frequencies, I'll almost certainly cut it up and make several smaller
loops with fewer wires for the higher frequencies.

Stick with a single wire and relatively few loops. More wire won't
make
the loop bigger, just harder to tune.

I don't think he meant to connect all those wires in parallel.
But, it would be a little tedious to connect each wire at one end to its
neighbor at the other end (of the loop), and _not_ create an ugly bird's
nest at the 'joint'.

Jonesy

Yep, it's a continuous single wire. If you used ribbon cable, you
would have to put a cut, and the jumper to jump over to the next
wire on each turn.. Would be a pain.
You just take a single length of wire and thread it around
through the holes until you have the number of turns you need.
You are moving over a row of holes on each turn.
The main thing to consider is you end up building the loop
and deciding the proper number of turns around the
capacitor you have, not the other way around.
A double 365pf cap "730 pf total if jumped together" will let
you be able to tune the whole AM-BC band with most loops.
My 44 inch per side diamond loop for MW has five turns.
My 16 inch diameter circle loop for MW uses 12 turns.
Both are using basically the same cap values.
I also use a single turn coupling loop that is inside and
slightly smaller than the main loop. But it does not effect
tuning, and it's size and spacing from the main loop is fairly
uncritical. The cap is in parallel with the main loop winding.
If you use a portable with a built in loop stick antenna,
you can just couple the radio to the loop and it will
work. But all my radios require a feed line to the antenna.

I would not be so quick to dismiss the ribbon wire on the basis of
capacitance build up ! If you start from the middle of one end by
joining
the two center wires together and from then on joining the end to end
wires
moving outwards what you have then done is to cancel not only the
capacitance build up but also the inductance build up.
You can then unfasten the first step on the center winding and feed it
from that point
i.e. center fed
Art

.... but a multi-turn loop in which the self-inductance cancelled wouldn't be
much of a receiving antenna! Production of EMF from the magnetic field
caused by current flowing in the adjacent turns and production of EMF from
the magnetic field component of an incident radio wave rely on the same
principle.

Chris

Receiving Loop Antenna Question
 

On Sun, 25 Jan 2009 09:11:19 -0800 (PST), Art Unwin
wrote:

what you have then done is to cancel not only the
capacitance build up but also the inductance build up

AKA Resistor

Receiving Loop Antenna Question
 

"christofire" wrote in message
...

"Art Unwin" wrote in message
...
On Jan 25, 3:51 am, wrote:
On Jan 23, 8:45 am, Allodoxaphobia wrote:



On Fri, 23 Jan 2009 13:57:40 +0000, dave wrote:
Ian Jackson wrote:

What about ribbon cable? I've got a fair length of ribbon cable
(something like 25 wires - the sort used in PCs to connect hard
drives
and the like) put away for a rainy-day loop antenna project. While I
could make one large loop using all 25 wires for the really low
frequencies, I'll almost certainly cut it up and make several
smaller
loops with fewer wires for the higher frequencies.

Stick with a single wire and relatively few loops. More wire won't
make
the loop bigger, just harder to tune.

I don't think he meant to connect all those wires in parallel.
But, it would be a little tedious to connect each wire at one end to
its
neighbor at the other end (of the loop), and _not_ create an ugly
bird's
nest at the 'joint'.

Jonesy

Yep, it's a continuous single wire. If you used ribbon cable, you
would have to put a cut, and the jumper to jump over to the next
wire on each turn.. Would be a pain.
You just take a single length of wire and thread it around
through the holes until you have the number of turns you need.
You are moving over a row of holes on each turn.
The main thing to consider is you end up building the loop
and deciding the proper number of turns around the
capacitor you have, not the other way around.
A double 365pf cap "730 pf total if jumped together" will let
you be able to tune the whole AM-BC band with most loops.
My 44 inch per side diamond loop for MW has five turns.
My 16 inch diameter circle loop for MW uses 12 turns.
Both are using basically the same cap values.
I also use a single turn coupling loop that is inside and
slightly smaller than the main loop. But it does not effect
tuning, and it's size and spacing from the main loop is fairly
uncritical. The cap is in parallel with the main loop winding.
If you use a portable with a built in loop stick antenna,
you can just couple the radio to the loop and it will
work. But all my radios require a feed line to the antenna.

I would not be so quick to dismiss the ribbon wire on the basis of
capacitance build up ! If you start from the middle of one end by
joining
the two center wires together and from then on joining the end to end
wires
moving outwards what you have then done is to cancel not only the
capacitance build up but also the inductance build up.
You can then unfasten the first step on the center winding and feed it
from that point
i.e. center fed
Art

... but a multi-turn loop in which the self-inductance cancelled wouldn't
be much of a receiving antenna! Production of EMF from the magnetic field
caused by current flowing in the adjacent turns and production of EMF from
the magnetic field component of an incident radio wave rely on the same
principle.

Chris



but thats they master theory behind art's antennas, they are self
destructive.

Receiving Loop Antenna Question
 

On Jan 25, 12:11*pm, "christofire" wrote:
"Art Unwin" wrote in message

...
On Jan 25, 3:51 am, wrote:



On Jan 23, 8:45 am, Allodoxaphobia wrote:

On Fri, 23 Jan 2009 13:57:40 +0000, dave wrote:
Ian Jackson wrote:

What about ribbon cable? I've got a fair length of ribbon cable
(something like 25 wires - the sort used in PCs to connect hard
drives
and the like) put away for a rainy-day loop antenna project. While I
could make one large loop using all 25 wires for the really low
frequencies, I'll almost certainly cut it up and make several smaller
loops with fewer wires for the higher frequencies.

Stick with a single wire and relatively few loops. More wire won't
make
the loop bigger, just harder to tune.

I don't think he meant to connect all those wires in parallel.
But, it would be a little tedious to connect each wire at one end to its
neighbor at the other end (of the loop), and _not_ create an ugly bird's
nest at the 'joint'.

Jonesy

Yep, it's a continuous single wire. If you used ribbon cable, you
would have to put a cut, and the jumper to jump over to the next
wire on each turn.. Would be a pain.
You just take a single length of wire and thread it around
through the holes until you have the number of turns you need.
You are moving over a row of holes on each turn.
The main thing to consider is you end up building the loop
and deciding the proper number of turns around the
capacitor you have, not the other way around.
A double 365pf cap "730 pf total if jumped together" will let
you be able to tune the whole AM-BC band with most loops.
My 44 inch per side diamond loop for MW has five turns.
My 16 inch diameter circle loop for MW uses 12 turns.
Both are using basically the same cap values.
I also use a single turn coupling loop that is inside and
slightly smaller than the main loop. But it does not effect
tuning, and it's size and spacing from the main loop is fairly
uncritical. The cap is in parallel with the main loop winding.
If you use a portable with a built in loop stick antenna,
you can just couple the radio to the loop and it will
work. But all my radios require a feed line to the antenna.

I would not be so quick to dismiss the ribbon wire on *the basis of
capacitance build up ! If you start from the middle of one end by
joining
the two center wires together and from then on joining the end to end
wires
moving outwards what you have then done is to cancel not only the
capacitance build up but also the inductance build up.
You can then unfasten the first step on the center winding and feed it
from that point
i.e. center fed
Art

... but a multi-turn loop in which the self-inductance cancelled wouldn't be
much of a receiving antenna! *Production of EMF from the magnetic field
caused by current flowing in the adjacent turns and production of EMF from
the magnetic field component of an incident radio wave rely on the same
principle.

Chris

As an experimenter I am inclined to give things a try. If everything
can be solved by the brain while sitting on the sofa then it would be
a waste of time! As a recieving antenna all you would need is wire
that has distributed loads and ZERO lumped loads, so why not just get
rid of the lumped loads via cancellation?
The complications that you bring up, I suggest, would be applicable to
transmitting antennas only
thus I feel experimentation is required before looking for a reason to
discard.
Sometimes an innocent experiment provides a long looked for answer to
the most complicated
question

Receiving Loop Antenna Question
 

"Art Unwin" wrote in message
...


snip

As an experimenter I am inclined to give things a try. If everything
can be solved by the brain while sitting on the sofa then it would be
a waste of time! As a recieving antenna all you would need is wire
that has distributed loads and ZERO lumped loads, so why not just get
rid of the lumped loads via cancellation?

Resonance? I think we already invented that.