Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz,
(Ham variety). Specs must also contain that it can withstand 80MPH wind and
30 Lbs of ICE?

Thanks and best DXin.

de Howard W3CQH

The KMA log antennas seem more durable than Create or Tennadyne but not
sure about 80mph wind + ice. They can make you one from thicker
materials that would probably survive.
Bob

Howard W3CQH wrote:
Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz,
(Ham variety). Specs must also contain that it can withstand 80MPH wind and
30 Lbs of ICE?

Thanks and best DXin.

de Howard W3CQH

Dear Howard W3CQH:

A 26:1 frequency range is difficult to do well. Might you intend 500
MHz to 1300 MHz? A 2.6:1 LPDA is reasonably straight forward with design
information in the ARRL Antenna Handbook (including mechanical information).

Use care when specifying survival of an antenna in terms of MPH. It is
the equivalent Newtons per square meter (pounds-force per square foot) that
is important. Several ways of describing wind speed exist and are not equal
in terms of what they do to an antenna structure. Ask for pressure
information.

I do not recognize the "30 Lb of ICE" specification. Most often, ice
loading is specified in terms of size such as 12 mm of ice all of the way
around each element (12 mm of radial ice).

It will help to know the task to be performed by the antenna. Tell us
more.

Regards, Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Howard W3CQH" wrote in message
news
Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz,
(Ham variety). Specs must also contain that it can withstand 80MPH wind
and
30 Lbs of ICE?

Thanks and best DXin.

de Howard W3CQH

On Sun, 18 Jun 2006 00:31:54 -0400, "J. Mc Laughlin"
wrote:


I do not recognize the "30 Lb of ICE" specification. Most often, ice
loading is specified in terms of size such as 12 mm of ice all of the way
around each element (12 mm of radial ice).

Given the looseness of use of the unit lb to specify mass and
(incorrectly) force, it is a bit ambiguous... but he probably means
mass. 30lbf of windage from ice loading isn't much on an antenna of
that type!

(We sin in the metric system as well! If someone asks me what I weigh
(being a force) I will answer in Kg (being a mass) instead of N
(force).)

Having said that, the impact of ice on the wind forces is probably
much more significant than the gravitational force due to the mass of
the ice.

Mac, I agree, radial ice loading is a more relevant specification.

Owen
--

"Owen Duffy" wrote in message
...
On Sun, 18 Jun 2006 00:31:54 -0400, "J. Mc Laughlin"
wrote:


I do not recognize the "30 Lb of ICE" specification. Most often, ice
loading is specified in terms of size such as 12 mm of ice all of the way
around each element (12 mm of radial ice).

Given the looseness of use of the unit lb to specify mass and
(incorrectly) force, it is a bit ambiguous... but he probably means
mass.

lbs is always force as far as i know. slugs is mass.

so long as we are confined to the planet earth, there is no difference
really. 1 kg (mass) always weighs 2.2 lbs (force). obviously if you go to
the moon ...

kilogram, slug -- mass
newton, pound -- force

Gravity

30lbf of windage from ice loading isn't much on an antenna of
that type!

(We sin in the metric system as well! If someone asks me what I weigh
(being a force) I will answer in Kg (being a mass) instead of N
(force).)

Having said that, the impact of ice on the wind forces is probably
much more significant than the gravitational force due to the mass of
the ice.

Mac, I agree, radial ice loading is a more relevant specification.

Owen
--

On Sun, 18 Jun 2006 07:10:56 -0500, "gravity"
wrote:


Given the looseness of use of the unit lb to specify mass and
(incorrectly) force, it is a bit ambiguous... but he probably means
mass.

lbs is always force as far as i know. slugs is mass.

so long as we are confined to the planet earth, there is no difference
really. 1 kg (mass) always weighs 2.2 lbs (force). obviously if you go to
the moon ...

kilogram, slug -- mass
newton, pound -- force


I was taught (in imperial units) to differentiate mass (pound) and
force (pound-force). That learning stood me well when we changed to SI
(metric) part way through school.

Practice may be different in different places, but I suspect that it
is laxness on the part of practitioners who refer to force in units of
pounds.

I just had a look at Wikipedia (which isn't the oracle), here is their
summary:

"The pound is the name of a number of units of mass, all in the range
of 300 to 600 grams. Most commonly, it refers to the avoirdupois pound
(exactly 453.59237 g), divided into 16 avoirdupois ounces. There is
also a unit of force corresponding to the avoirdupois pound, see
pound-force."

Wikpedia highlights just another aspect of the unit, its flexibility!

Owen
PS: a slug is a unit of mass, and equivalent to about 14.6Kg or
32.2lbs. I don't think it is in wide use!
--

Owen Duffy wrote:


I was taught (in imperial units) to differentiate mass (pound) and
force (pound-force). That learning stood me well when we changed to SI
(metric) part way through school.


You were taught wrong. If you use pounds in a formula that wants mass
such as F=M*A you will get the wrong answer. So lets say you weigh 200
lbs on earth where A = 32 ft/sec^2. You can then calculate your mass by
solving for M = F/A or 200/32 = 6.25.

When you are doing physical calculations it is very important to use the
correct units, other wise you calculations are meaningless. Suppose you
want to know what you will weigh on the moon where the acceleration due
to gravity is 5.25 ft/sec^2. F = M*A if you use 200 for your mass you
get, 200 * 5.25 = 1050, that indicates you would weigh 1050 lbs on the
moon. Which is clearly wrong. Trying again with the correct units and
you get, 6.25 * 5.25 = 32.8, now that sounds more like what you would
weight on the moon.

In the non scientific world, where the metric unit KG is used for
weight, M=F*A works just fine if you put what you call "weight" in KG in
for M in the formula.

It's arguable which method is better, using mass or force units for
weight. What you want to know is do you need to change your weight, if
the doctor tells you that you need to loose weight, that's easy just
move to the moon, done. What he really wants is for you to loose mass.
So your weight (force) can change with gravity, but your mass doesn't
change. Unless of course you loose weight


--
Chris W
KE5GIX

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give the gifts they want
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from anywhere, for any occasion!
http://thewishzone.com

"Owen Duffy" wrote in message
...
On Sun, 18 Jun 2006 07:10:56 -0500, "gravity"
wrote:


Given the looseness of use of the unit lb to specify mass and
(incorrectly) force, it is a bit ambiguous... but he probably means
mass.

lbs is always force as far as i know. slugs is mass.

so long as we are confined to the planet earth, there is no difference
really. 1 kg (mass) always weighs 2.2 lbs (force). obviously if you go
to
the moon ...

kilogram, slug -- mass
newton, pound -- force


I was taught (in imperial units) to differentiate mass (pound) and
force (pound-force). That learning stood me well when we changed to SI
(metric) part way through school.

Practice may be different in different places, but I suspect that it
is laxness on the part of practitioners who refer to force in units of
pounds.

I just had a look at Wikipedia (which isn't the oracle), here is their
summary:

"The pound is the name of a number of units of mass, all in the range
of 300 to 600 grams. Most commonly, it refers to the avoirdupois pound
(exactly 453.59237 g), divided into 16 avoirdupois ounces. There is
also a unit of force corresponding to the avoirdupois pound, see
pound-force."

Wikpedia highlights just another aspect of the unit, its flexibility!

Owen
PS: a slug is a unit of mass, and equivalent to about 14.6Kg or
32.2lbs. I don't think it is in wide use!
--

i first heard of slugs at age 7, but i've never seen them used in an
engineering class.

we used SI almost exclusively in university and high school. i was taught
there that pounds is a unit of force (not mass). however Wikipedia claims
pounds is a standardized unit of mass, not force.

so we are both right really.

as i've noted in another post, 1 slug at in Earth's gravitational field is ~
32 pounds, so it's a convenient unit to use.

so basically if NIST (or whoever) defines it as mass, then we are stuck with
it.

"honey do i look fat in this dress?"
"no baby, you are no more than 5 slugs or so."

Gravity

Dear Owen:
As you, and others, have concluded from my descriptions, I too have mass
and force in separate bins.
I continue to be amazed at the facility with which MEs use "pounds" to
indicate just what they want it to indicate. Every time that I do a
mechanical design (or check a mechanical design), I convert to SI units with
a careful check accompanying the conversion of whether I have converted
forces or masses. Once in SI, everything is easy.

I have had discussions with some of my fellow P.E.s of the ME persuasion
about this: they contend that they always know when force and mass is
involved. I remain unconvinced.

A mass centered system (SI) is more straight forward than a force
centered system where an assumed gravitational field is used.

Here in the North, ice plus a moderate amount of wind is most often what
kills antennas having cantilevered elements.

Thanks for your comments.

73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Owen Duffy" wrote in message
...
On Sun, 18 Jun 2006 00:31:54 -0400, "J. Mc Laughlin"
wrote:


I do not recognize the "30 Lb of ICE" specification. Most often, ice
loading is specified in terms of size such as 12 mm of ice all of the way
around each element (12 mm of radial ice).

Given the looseness of use of the unit lb to specify mass and
(incorrectly) force, it is a bit ambiguous... but he probably means
mass. 30lbf of windage from ice loading isn't much on an antenna of
that type!

(We sin in the metric system as well! If someone asks me what I weigh
(being a force) I will answer in Kg (being a mass) instead of N
(force).)

Having said that, the impact of ice on the wind forces is probably
much more significant than the gravitational force due to the mass of
the ice.

Mac, I agree, radial ice loading is a more relevant specification.

Owen
--

"Howard W3CQH" wrote in message
news
Looking for specs on any log periodic antenna that covers 50Mhz - 1300Mhz,
(Ham variety). Specs must also contain that it can withstand 80MPH wind
and
30 Lbs of ICE?

Thanks and best DXin.

de Howard W3CQH



http://www.eham.net/reviews/detail/1700 for starters