That's what they use for mainstay antennas on yachts. they work well (the
groundplane helps of course).

Brad VK2QQ

"Dave" wrote in message
news
I recently acquired a large quantity of very flexible stranded
stainless steel wire at a garage sale. It is about 0.85 mm (around
1/32 inch) in diameter and extremely strong. I was wondering if this
could be used for wire antennas for HF. I seem to remember seeing
something about SS not being ideal. Is this a real consideration or
just a matter of being too finiky?

Thanks - Dave

You've gotten a lot of conflicting advice. Let me add mine.

Without going through the numbers in detail, Paul, OH3LWR's analysis
looks sound. However, he neglected one factor. The skin depth is also
inversely proportional to the square root of the permeability. Some
stainless steels are ferromagnetic, with a permeability I'd guess at 100
or more. That reduces the skin depth, and therefore increases the RF
resistance, by at least a factor of 10. If you do the analysis with
realistic numbers, you'll find that loss can become at least several dB
if the wire is magnetic, and worse with longer (40 or 80 meter) dipole
lengths.

So my recommendation is to check the wire with a magnet. If it's
magnetic, expect longer antennas to be quiet and broadband (which
amateurs crave) but lossy (which most don't seem to care about).
Non-magnetic stainless isn't likely to produce objectionable loss,
except perhaps at an 80 meter dipole length or longer.

You can get a qualitative feel for the loss by comparing the 2:1 SWR
bandwidth of an antenna made from the wire with the bandwidth from a
dipole made from copper wire. The broader it is, the lossier it is.

Roy Lewallen, W7EL

Dave wrote:
I recently acquired a large quantity of very flexible stranded
stainless steel wire at a garage sale. It is about 0.85 mm (around
1/32 inch) in diameter and extremely strong. I was wondering if this
could be used for wire antennas for HF. I seem to remember seeing
something about SS not being ideal. Is this a real consideration or
just a matter of being too finiky?

Thanks - Dave

More succinctly, it all boils down to -

Copper antenna wires are so efficient (say 98 percent) an increase in loss
by 10 times (down to 80 percent) is not noticeable.
---
Reg

On Tue, 24 Aug 2004 12:48:29 -0700, Roy Lewallen
wrote:

Without going through the numbers in detail, Paul, OH3LWR's analysis
looks sound. However, he neglected one factor. The skin depth is also
inversely proportional to the square root of the permeability. Some
stainless steels are ferromagnetic, with a permeability I'd guess at 100
or more. That reduces the skin depth, and therefore increases the RF
resistance, by at least a factor of 10.

My skin depth figures are base upon a quick web search, so I have no
idea how typical these figures might be or is it likely that the OP
would have a similar wire.

If you do the analysis with
realistic numbers, you'll find that loss can become at least several dB
if the wire is magnetic, and worse with longer (40 or 80 meter) dipole
lengths.

If my original assumptions are correct, the original poster (OP)
should also check the dissipation of each meter of antenna conductor,
since above 1.8 MHz, it appears that the power dissipation per meter
is slightly higher than at 1.8 MHz, thus the wire temperature is
higher (and might even affect the sag of the wire when
transmitting:-).

So my recommendation is to check the wire with a magnet. If it's
magnetic, expect longer antennas to be quiet and broadband (which
amateurs crave) but lossy (which most don't seem to care about).
Non-magnetic stainless isn't likely to produce objectionable loss,
except perhaps at an 80 meter dipole length or longer.

In addition, since the OP had a large quantity of the wire, I would
suggest building a conical dipole antenna from the wire. Not only will
the current (and losses) in each leg be lower, but also the bandwidth
would be larger.

Paul OH3LWR

This is interesting. Are the negative effects due to the fact that induced
magnetism will persist, and thus set up additional impedence on the line ?
and does this skin effect caused by the magnetism vary significantly with
frequency ?

"Roy Lewallen" wrote in message
...
You've gotten a lot of conflicting advice. Let me add mine.

Without going through the numbers in detail, Paul, OH3LWR's analysis
looks sound. However, he neglected one factor. The skin depth is also
inversely proportional to the square root of the permeability. Some
stainless steels are ferromagnetic, with a permeability I'd guess at 100
or more. That reduces the skin depth, and therefore increases the RF
resistance, by at least a factor of 10. If you do the analysis with
realistic numbers, you'll find that loss can become at least several dB
if the wire is magnetic, and worse with longer (40 or 80 meter) dipole
lengths.

So my recommendation is to check the wire with a magnet. If it's
magnetic, expect longer antennas to be quiet and broadband (which
amateurs crave) but lossy (which most don't seem to care about).
Non-magnetic stainless isn't likely to produce objectionable loss,
except perhaps at an 80 meter dipole length or longer.

You can get a qualitative feel for the loss by comparing the 2:1 SWR
bandwidth of an antenna made from the wire with the bandwidth from a
dipole made from copper wire. The broader it is, the lossier it is.

Roy Lewallen, W7EL

Dave wrote:
I recently acquired a large quantity of very flexible stranded
stainless steel wire at a garage sale. It is about 0.85 mm (around
1/32 inch) in diameter and extremely strong. I was wondering if this
could be used for wire antennas for HF. I seem to remember seeing
something about SS not being ideal. Is this a real consideration or
just a matter of being too finiky?

Thanks - Dave


---
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Hal Rosser wrote:

This is interesting. Are the negative effects due to the fact that induced
magnetism will persist, and thus set up additional impedence on the line ?

Not if I understand you correctly. The effect I'm describing isn't an
impedance due to inductance, as you seem to imply. It's that the density
of an AC current decays exponentially from the surface downward into a
conductor, increasing the resistance of that conductor (known as skin
effect). The skin depth is a measure of how rapidly it decays and
therefore how resistive a conductor will be, and the skin depth is a
function of the frequency, the DC conductivity of the material, and its
permeability. I'm sorry I'm not able to explain why increased
permeability decreases the skin depth except that it's due to the
increased magnetic field opposing current into the conductor (which
might be what you tried to say). I'm sure you can find a lot about skin
effect on the web, as well as in any electromagnetics text.

and does this skin effect caused by the magnetism vary significantly with
frequency ?

I honestly don't know the answer to this. The permeability of
ferromagnetic materials does vary with frequency, in what appears to be
an unpredictable way. Whether this value or the DC permeability should
be used for calculation, I don't know. I suspect that the DC
permeability should be used, and the permeability change with frequency
regarded as a change in effective permeability -- but I don't know for
sure. I'd really appreciate it if anyone who does know would comment. Of
course, skin depth varies with frequency even if the permeability is
constant.

Roy Lewallen, W7EL

Roy, W7EL wrote:
"Some stainless steels are ferromagnetic, with a permability I`d guess
at 100 or more. That reduces the skin depth, and therefore increases the
RF resistance by a factor of 10."

Being ferromagnetic does not disqualify an antenna material. Most CB
whips are stainless steel. They aren`t too lossy because they are only
about 1/4-wave at 27 MHz and must be large enough in diameter to be
durable. In the range of 0.55 MHz to 1.7 MHz, most transmission is from
ordinary non-stainless steel towers. The only coating on many of these
is paint. The cross-section to length ratio is economically small, but I
doubt the loss added by using nonplated steel could be measured.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote in message
...
Roy, W7EL wrote:
"Some stainless steels are ferromagnetic, with a permability I`d guess
at 100 or more. That reduces the skin depth, and therefore increases the
RF resistance by a factor of 10."

Being ferromagnetic does not disqualify an antenna material.

Whoa... now you are misquoting Roy.

He never did DISQUALIFY the use of stainless steel
He clearly stated in technical terms what stainless steel
lacked in an area that is important with respect to radiation.
I suspect the use of stainless steel for consumer antennas
is an engineering one to prevent rust and antenna mechanical distortion
which outways the loss in efficiency.
It was this difference that Roy was alluding to and is the reason why
amateurs take note of the characteristics of material used and is why
aluminum,copper and the like
is used in the communication world. Many in the amateur community allude to
communication obtained with a wet string but in no way are they
DISQUALIFYING the use of aluminum and the like. Stop throwing mud and get
with the program. You will never,ever make the smallest piece of your mud
stick to the likes of Roy and Tom with mis quotations.
Art
Art



Most CB
whips are stainless steel. They aren`t too lossy because they are only
about 1/4-wave at 27 MHz and must be large enough in diameter to be
durable. In the range of 0.55 MHz to 1.7 MHz, most transmission is from
ordinary non-stainless steel towers. The only coating on many of these
is paint. The cross-section to length ratio is economically small, but I
doubt the loss added by using nonplated steel could be measured.

Best regards, Richard Harrison, KB5WZI

On Thu, 26 Aug 2004 16:05:46 GMT, "
wrote:
Stop throwing mud

more trolling

I suspect the use of stainless steel for consumer antennas
is an engineering one to prevent rust and antenna mechanical distortion
which outways the loss in efficiency.

================================

Your suspicion is well founded.

ECONOMICS INVARIABLY RULES.
---
Reg