I'm in the process of building a homebrew Cobwebb Ariel.

I have found two different sizes for the twin cable elements, figure 8 42
strand 0.2mm, but on the Cobwebb web site it says figure 8 84 strand.

Also in the Cobwebb revealed PDF doc that I downloaded on page 5 it says
each core is 42 strands of 0.2mm diameter and on page 7 of the same doc it
says figure 8 84 strand. So I'm a little confused.

Does anyone know what is the correct cable to use, 42 strand 0.2mm or 84
strand 0.2mm?

Many thanks

In article ,
Barrett wrote:

I'm in the process of building a homebrew Cobwebb Ariel.

I have found two different sizes for the twin cable elements, figure 8 42
strand 0.2mm, but on the Cobwebb web site it says figure 8 84 strand.

Also in the Cobwebb revealed PDF doc that I downloaded on page 5 it says
each core is 42 strands of 0.2mm diameter and on page 7 of the same doc it
says figure 8 84 strand. So I'm a little confused.

Does anyone know what is the correct cable to use, 42 strand 0.2mm or 84
strand 0.2mm?

As I read it, this is two-conductor "zipcord" cable, with 42 strands
in each of two separate conductors, for a total of 84 strands.

I doubt that the wire gauge or strand count is very significant, let
alone critical. You could probably build this from whatever sort of
stranded zipcord-type loudspeaker or appliance-wire cable you have
locally available (as long as it's not too thin-gauge) without
noticing a significant electrical difference.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Ok Dave, I will see what I have in the shed.
Trouble I have is that I only have a SWR meter to do the tuning and I have
heard the thickness of the wire can change the length of wire used by quit a
lot. So I really needed to get it very close for the tuning as I don't have
an analyzer to use.

Thanks



"Dave Platt" wrote in message
...
In article ,
Barrett wrote:

I'm in the process of building a homebrew Cobwebb Ariel.

I have found two different sizes for the twin cable elements, figure 8 42
strand 0.2mm, but on the Cobwebb web site it says figure 8 84 strand.

Also in the Cobwebb revealed PDF doc that I downloaded on page 5 it says
each core is 42 strands of 0.2mm diameter and on page 7 of the same doc it
says figure 8 84 strand. So I'm a little confused.

Does anyone know what is the correct cable to use, 42 strand 0.2mm or 84
strand 0.2mm?

As I read it, this is two-conductor "zipcord" cable, with 42 strands
in each of two separate conductors, for a total of 84 strands.

I doubt that the wire gauge or strand count is very significant, let
alone critical. You could probably build this from whatever sort of
stranded zipcord-type loudspeaker or appliance-wire cable you have
locally available (as long as it's not too thin-gauge) without
noticing a significant electrical difference.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Question about the elements.

Does the speaker wire need to be kept very straight (no twisting) or doesn't
it matter if there twisted?

Thanks



"Barrett" wrote in message
o.uk...
Ok Dave, I will see what I have in the shed.
Trouble I have is that I only have a SWR meter to do the tuning and I
have heard the thickness of the wire can change the length of wire used by
quit a lot. So I really needed to get it very close for the tuning as I
don't have an analyzer to use.

Thanks



"Dave Platt" wrote in message
...
In article ,
Barrett wrote:

I'm in the process of building a homebrew Cobwebb Ariel.

I have found two different sizes for the twin cable elements, figure 8 42
strand 0.2mm, but on the Cobwebb web site it says figure 8 84 strand.

Also in the Cobwebb revealed PDF doc that I downloaded on page 5 it says
each core is 42 strands of 0.2mm diameter and on page 7 of the same doc
it
says figure 8 84 strand. So I'm a little confused.

Does anyone know what is the correct cable to use, 42 strand 0.2mm or 84
strand 0.2mm?

As I read it, this is two-conductor "zipcord" cable, with 42 strands
in each of two separate conductors, for a total of 84 strands.

I doubt that the wire gauge or strand count is very significant, let
alone critical. You could probably build this from whatever sort of
stranded zipcord-type loudspeaker or appliance-wire cable you have
locally available (as long as it's not too thin-gauge) without
noticing a significant electrical difference.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Wed, 27 Feb 2008 17:21:01 GMT, "Barrett"
wrote:

Question about the elements.

Does the speaker wire need to be kept very straight (no twisting) or doesn't
it matter if there twisted?

Ok Dave, I will see what I have in the shed.
Trouble I have is that I only have a SWR meter to do the tuning and I
have heard the thickness of the wire can change the length of wire used by
quit a lot. So I really needed to get it very close for the tuning as I
don't have an analyzer to use.

For wire running in a zip cord, point-to-point, you will use more wire
by twisting than running straight. This will affect the tune if, as
you say, length is critical.

As for being critical; there are many variables that contribute to the
state of tune, wire length being one of them, but not the sole
variable. The presence or absence of insulation, and how thick it is
will be another variable. Proximity to other materials in the
construction will be yet another variable. Proximity to other
environmental disturbances will contribute more variables. You are
almost guaranteed to not be resonant the first time.

Your SWR meter is sufficient for the purposes of tuning your antenna.
Simply take readings at close frequency intervals to chart a curve of
match (or mismatch as the case may be). Do this with the antenna IN
PLACE. Note from this curve how much you are off your desired
frequency. Make a slight (emphasis on slight) adjustment and repeat
the curve building exercise with the antenna IN PLACE. You will now
have a reference (the first curve) and a delta (the difference between
the reference and your second curve). This should tell you how much
you need to adjust to achieve match.

73's
Richard Clark, KB7QHC

In article ,
Barrett wrote:

Ok Dave, I will see what I have in the shed.
Trouble I have is that I only have a SWR meter to do the tuning and I
have heard the thickness of the wire can change the length of wire used by
quit a lot. So I really needed to get it very close for the tuning as I
don't have an analyzer to use.

At these frequencies, the diameter of the wire is such a small
fraction of the antenna's length that small changes in the diameter
aren't going to matter very much.

As far as tuning and reproducibility goes, there's going to be a
bigger issue with this sort of antenna design (or any made from this
type of wire) - stretching of the wire under tension. This sort of
stranded, soft-drawn copper wire is prone to stretch quite a bit under
tension, both immediately and over time. You're likely to find the
antenna's tuning changing a bit, at least, over the course of its
lifetime, as the wires sag and stretch under their own weight.

Wire antennas are often made of "hard-drawn" copper wire, or of
soft-drawn wire which is pre-stretched to avoid such sagging and
de-tuning. I'm not sure whether zipcord-type appliance or speaker
wire could/should be pre-stretched in this way - I suspect that the
PVC insulation might be weakened by doing so and that the wire might
snap.

Question about the elements.

Does the speaker wire need to be kept very straight (no twisting) or doesn't
it matter if there twisted?

I wouldn't twist it tightly - this _might_ add enough inductance to
alter the tuning by a detectable amount. A bit of loose twisting
ought not to matter. I don't think you have to be pedantic about
keeping it absolutely un-twisted.

As to tuning and SWR - as long as your rig has some sort of basic
autotuner that can handle a moderate SWR (say, 3:1 or better), and as
long as you get the antenna's tuning reasonably close (SWR minimum
somewhere inside each band you're going to be using), and as long as
you use a not-too-terribly-long run of good coax (RG-8 thickness
preferred), I really don't think you have to worry about trying to get
the lowest-possible SWR for the antenna itself. At HF, the amount of
"excess loss" in the cable, and in the ATU due to a moderate SWR is
not large, and probably will not make an appreciable difference in
your ability to either hear or be heard.



--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

The only thing left that I'm not sure about is the true length of the
element for 17m. I have read that the length on page 4 of Cobwebb revealed
for this band is wrong.

It says the Tapping point 2300 and the length 4400.

Is the Tapping point correct and the length wrong or are they both wrong?

What should they both be?

Many thanks


"Dave Platt" wrote in message
...
In article ,
Barrett wrote:

Ok Dave, I will see what I have in the shed.
Trouble I have is that I only have a SWR meter to do the tuning and I
have heard the thickness of the wire can change the length of wire used
by
quit a lot. So I really needed to get it very close for the tuning as I
don't have an analyzer to use.

At these frequencies, the diameter of the wire is such a small
fraction of the antenna's length that small changes in the diameter
aren't going to matter very much.

As far as tuning and reproducibility goes, there's going to be a
bigger issue with this sort of antenna design (or any made from this
type of wire) - stretching of the wire under tension. This sort of
stranded, soft-drawn copper wire is prone to stretch quite a bit under
tension, both immediately and over time. You're likely to find the
antenna's tuning changing a bit, at least, over the course of its
lifetime, as the wires sag and stretch under their own weight.

Wire antennas are often made of "hard-drawn" copper wire, or of
soft-drawn wire which is pre-stretched to avoid such sagging and
de-tuning. I'm not sure whether zipcord-type appliance or speaker
wire could/should be pre-stretched in this way - I suspect that the
PVC insulation might be weakened by doing so and that the wire might
snap.

Question about the elements.

Does the speaker wire need to be kept very straight (no twisting) or
doesn't
it matter if there twisted?

I wouldn't twist it tightly - this _might_ add enough inductance to
alter the tuning by a detectable amount. A bit of loose twisting
ought not to matter. I don't think you have to be pedantic about
keeping it absolutely un-twisted.

As to tuning and SWR - as long as your rig has some sort of basic
autotuner that can handle a moderate SWR (say, 3:1 or better), and as
long as you get the antenna's tuning reasonably close (SWR minimum
somewhere inside each band you're going to be using), and as long as
you use a not-too-terribly-long run of good coax (RG-8 thickness
preferred), I really don't think you have to worry about trying to get
the lowest-possible SWR for the antenna itself. At HF, the amount of
"excess loss" in the cable, and in the ATU due to a moderate SWR is
not large, and probably will not make an appreciable difference in
your ability to either hear or be heard.



--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

The cable used for the Cobwebb is:-

A very heavy duty twin cable with a 'figure 8' profile ideal for high
power speaker connection suitable for power amplifiers up to 500W
output.
42/0.15mm plain copper conductor
Rating 60V rms 6A
Overall size 5.7 x 2.9mm
Sheathed in white PVC with black polarity identification stripe

You can find it on the RAPID ELECTRONICS website at www.rapidonline.com
Part No. 01-0157.

Regards

Steve
================================================

On Feb 26, 9:34 pm, "Barrett" wrote:
I'm in the process of building a homebrew Cobwebb Ariel.

I have found two different sizes for the twin cable elements, figure 8 42
strand 0.2mm, but on the Cobwebb web site it says figure 8 84 strand.

Also in the Cobwebb revealed PDF doc that I downloaded on page 5 it says
each core is 42 strands of 0.2mm diameter and on page 7 of the same doc it
says figure 8 84 strand. So I'm a little confused.

Does anyone know what is the correct cable to use, 42 strand 0.2mm or 84
strand 0.2mm?

Many thanks

Hi Steve
Do you have the correct measurement for the 17m element?

A lot of people say 4400 is incorrect as its too long.

Many thanks


wrote in message
...
The cable used for the Cobwebb is:-

A very heavy duty twin cable with a 'figure 8' profile ideal for high
power speaker connection suitable for power amplifiers up to 500W
output.
42/0.15mm plain copper conductor
Rating 60V rms 6A
Overall size 5.7 x 2.9mm
Sheathed in white PVC with black polarity identification stripe

You can find it on the RAPID ELECTRONICS website at www.rapidonline.com
Part No. 01-0157.

Regards

Steve
================================================

On Feb 26, 9:34 pm, "Barrett" wrote:
I'm in the process of building a homebrew Cobwebb Ariel.

I have found two different sizes for the twin cable elements, figure 8 42
strand 0.2mm, but on the Cobwebb web site it says figure 8 84 strand.

Also in the Cobwebb revealed PDF doc that I downloaded on page 5 it says
each core is 42 strands of 0.2mm diameter and on page 7 of the same doc
it
says figure 8 84 strand. So I'm a little confused.

Does anyone know what is the correct cable to use, 42 strand 0.2mm or 84
strand 0.2mm?

Many thanks

The measurements in the booklet were taken from an actual cobwebb.

The lengths and tapping points for the Tee match, need to be adjusted
during the initial tests.

An Antenna Analyser is very helpful during set-up and you may have to
beg or borrow one for testing.

However, in tests, the following dimensions have been used
successfully:-

Band Element Length Shorting point
10M 2540 mm 1560 mm
12M 2930 mm 1790 mm
15M 3450 mm 2080 mm
17M 4060 mm 2220 mm
20M 5150 mm 2720 mm

Hope this helps

Steve.
=============================================
On Feb 28, 7:47*pm, "Barrett" wrote:
Hi Steve
Do you have the correct measurement for the 17m element?

A lot of people say 4400 is incorrect as its too long.

Many thanks

wrote in message

...



The cable used for the Cobwebb is:-

A very heavy duty twin cable with a 'figure 8' profile ideal for high
power speaker connection suitable for power amplifiers up to 500W
output.
42/0.15mm plain copper conductor
Rating 60V rms 6A
Overall size 5.7 x 2.9mm
Sheathed in white PVC with black polarity identification stripe

You can find it on the RAPID ELECTRONICS website atwww.rapidonline.com
Part No. 01-0157.

Regards

Steve
================================================

On Feb 26, 9:34 pm, "Barrett" wrote:
I'm in the process of building a homebrew Cobwebb Ariel.

I have found two different sizes for the twin cable elements, figure 8 42
strand 0.2mm, but on the Cobwebb web site it says figure 8 84 strand.

Also in the Cobwebb revealed PDF doc that I downloaded on page 5 it says
each core is 42 strands of 0.2mm diameter and on page 7 of the same doc
it
says figure 8 84 strand. So I'm a little confused.

Does anyone know what is the correct cable to use, 42 strand 0.2mm or 84
strand 0.2mm?

Many thanks- Hide quoted text -

- Show quoted text -