Anyone have experience making a dipole from 18 gauge speaker wire? I
have a whole lot of it lying around the house, and was wondering if I
could put it to some good use.

KD2AIP wrote in news:e5bba3fc-510d-49a2-b392-
:

Anyone have experience making a dipole from 18 gauge speaker wire? I
have a whole lot of it lying around the house, and was wondering if I
could put it to some good use.

If it is copper wire, it is more suitable than many things proposed for
antenna conductor, though annealed copper is relatively low strength
material.

Opinions vary, but wire insulation contributes little, if any, strength,
but substantially increases wind resistance and mass, so it compromises
the ability to withstand high winds.

The next question often asked in your situation is whether the speaker
wire makes a good feedline. Contrary to popular belief, PVC insulated
figure-8 cable is not a good feedline for HF antennas.

Owen

PS: hams universally ignore the guidance of NFPA 70 which makes
recommendation on conductors for antennas.

On 7/31/2011 4:02 PM, Owen Duffy wrote:

Owen

PS: hams universally ignore the guidance of NFPA 70 which makes
recommendation on conductors for antennas.

Maybe because NFPA 70 costs $150 US?

John

John S wrote in :


Maybe because NFPA 70 costs $150 US?


Yes, standards are expensive things and it is a frustration when
researching.

Anyway, NFPA makes recommendation on the wires for ham antennas
specifically, and it may be binding in some places.

I suspect the reason for ignoring it is that the advice is unaccepable
to most hams.

That said, it does seem over the top in some areas, and is hardly
comprehensive in its thinking. For example, the prescription for
feedlines seems to not be aware of the existence and use of coax.

I guess it is these gaps that give critics the basis for arguing against
the whole thing.

Anyway, in respect of antenna wires, it does not 'permit' annealled
copper or other low strength materials, and it 'requires' a minimum
conductor diameter of #14 for up to 150' span.

They may have had in mind the risk to persons and property where low
strength conductor are broken in high wind and make contact with power
lines.

Owen

On 7/31/2011 3:26 PM, Owen Duffy wrote:
John wrote in :


Maybe because NFPA 70 costs $150 US?


Yes, standards are expensive things and it is a frustration when
researching.

Anyway, NFPA makes recommendation on the wires for ham antennas
specifically, and it may be binding in some places.

I suspect the reason for ignoring it is that the advice is unaccepable
to most hams.

That said, it does seem over the top in some areas, and is hardly
comprehensive in its thinking. For example, the prescription for
feedlines seems to not be aware of the existence and use of coax.

You refer to the "continuously enclosed metallic shield", I suspect.


I guess it is these gaps that give critics the basis for arguing against
the whole thing.

Anyway, in respect of antenna wires, it does not 'permit' annealled
copper or other low strength materials, and it 'requires' a minimum
conductor diameter of #14 for up to 150' span.

They may have had in mind the risk to persons and property where low
strength conductor are broken in high wind and make contact with power
lines.


That is precisely why. (ice loads, too)

On 8/1/2011 7:52 PM, Jim Lux wrote:
On 7/31/2011 3:26 PM, Owen Duffy wrote:
John wrote in :


Maybe because NFPA 70 costs $150 US?


Yes, standards are expensive things and it is a frustration when
researching.

Anyway, NFPA makes recommendation on the wires for ham antennas
specifically, and it may be binding in some places.

I suspect the reason for ignoring it is that the advice is unaccepable
to most hams.

That said, it does seem over the top in some areas, and is hardly
comprehensive in its thinking. For example, the prescription for
feedlines seems to not be aware of the existence and use of coax.

You refer to the "continuously enclosed metallic shield", I suspect.


I guess it is these gaps that give critics the basis for arguing against
the whole thing.

Anyway, in respect of antenna wires, it does not 'permit' annealled
copper or other low strength materials, and it 'requires' a minimum
conductor diameter of #14 for up to 150' span.

They may have had in mind the risk to persons and property where low
strength conductor are broken in high wind and make contact with power
lines.


That is precisely why. (ice loads, too)

NFPA (according to what you posted) requires heavier gauge wire for
transmitting than for receiving. Transmitting makes the wire weigh more?

On 7/31/2011 3:09 PM, John S wrote:
On 7/31/2011 4:02 PM, Owen Duffy wrote:

Owen

PS: hams universally ignore the guidance of NFPA 70 which makes
recommendation on conductors for antennas.

Maybe because NFPA 70 costs $150 US?

John

Free at the library, and at various sites for California Title 24.
http://rrdocs.nfpa.org/rrserver/brow...tricalCode2010

And the sections on antennas are widely quoted. I don't think cost of a
copy of the code is why hams don't follow it.

here you go:
II Receiving Equipment - Antenna Systems
Article 810.16 Size of Wire-Strung Antenna -Receiving Station
(A) Size of Antenna Conductors. Outdoor antenna conductors for
receiving stations shall be of a size not less than given in Table 810.16(A)
Table 810.16(A) Size of Receiving Station Outdoor Antenna Conductors
Minimum size of Conductors (AWG) where Maximum Open Span Length is:
Less than 11m 11m to 45m Over 45m
Al Alloy, hard
drawn copper 19 14 12

Cu Clad Steel,
Bronze, other high
strength matl 20 17 14

Or
III Amateur Transmitting and Receiving Stations - Antenna Systems
less than 45 m over 45 m
Hard drawn copper AWG 14 AWG 10
CCS, bronze, etc. AWG 14 AWG 12

Jim Lux wrote in
:

....
III Amateur Transmitting and Receiving Stations - Antenna Systems
less than 45 m over 45 m
Hard drawn copper AWG 14 AWG 10
CCS, bronze, etc. AWG 14 AWG 12

Examples 7 and 8 in the catenary calculator at
http://vk1od.net/calc/awcc/awcc.htm use #14 and #10 HDC. Readers can
explore the survivability of wind and ice with the calculator.

If I model a 45m simple span of #14 HDC at the lowest wind speeds
applicable to the design of structures in this jurisdiction, using the
mandated safety factor, the minimum sag is about 5% of span, about as
large as it typically practical for such a span.

NFPA 70 does not apply in VK, though there are standards that apply and
the answer comes up pretty much the same, just there is more freedom in
engineering shorter spans.

Owen

On 7/31/2011 2:02 PM, Owen Duffy wrote:


PS: hams universally ignore the guidance of NFPA 70 which makes
recommendation on conductors for antennas.

Are you saying the electrical code is sort of like the pirate code? more
guidelines than actual requirements?

I think the way that hams can rationalize it is that most wire antennas
(particularly those made with fine wire) are, by their nature,
"temporary installations". The finer the wire, the more temporary.

On 8/1/2011 20:42, Jim Lux wrote:
On 7/31/2011 2:02 PM, Owen Duffy wrote:


PS: hams universally ignore the guidance of NFPA 70 which makes
recommendation on conductors for antennas.

Are you saying the electrical code is sort of like the pirate code? more
guidelines than actual requirements?

I think the way that hams can rationalize it is that most wire antennas
(particularly those made with fine wire) are, by their nature,
"temporary installations". The finer the wire, the more temporary.

The National Electric Code limits the use of Temporary installations to
power and lighting conductors.

"ARTICLE 527 Temporary Installations
527.1 Scope.
The provisions of this article apply to temporary electrical power and
lighting installations." Copyright 2002 the National Fire Protection
Association.

--
Tom Horne, W3TDH