I've seen real-life cases with high-Q microstrip structures where gold
plating actually caused a significant lowering of efficiency. As you
point out, nickel is used as a barrier metal to prevent alloying of the
gold with the underlying copper. If the gold isn't at least several skin
depths thick, significant current flows in the nickel. Nickel is a
particularly poor RF conductor, very much worse than copper, because the
skin depth in nickel is decreased dramatically by its ferromagnetic
permeability. So, if you're able to calculate skin depth, and know what
you're doing, and are willing to use quite a bit of gold (particularly
necessary at HF and below) you can achieve efficiency with gold plating
that's pretty much indistinguishable from that of copper. If you don't
know what you're doing, it is possible to substantially degrade the
efficiency by gold plating. I'm sure somebody could be conned into
buying one, though.

Roy Lewallen, W7EL

Gary V. Deutschmann, Sr. wrote:

Hi Gang

Since the radiation of an antenna is done primarily on the surface of
the elements (or wire) would gold plating the elements increase the
efficiency of the antenna in any way?

Gold sounds expensive, but if thin enough, one ounce of gold could
plate an entire football field. Brass corrods, nickel is usually used
as the first plating before another metal like gold is plated over
that. If the cost for gold over the cost of brass is only about 1
buck per foot of element length, making cost not relavent to the
question. Would a gold plated antenna work better than aluminum or
nickel plated?

TTUL
Gary

Hi Roy;
It's worse than that: Copper will diffuse throught the gold and pile up on
the surface.
I showed that with an Auger microprobe at Motorola decades ago.
So to go to a gold surface, nickel is mandatory, then a thick gold coating;
Too expensive!
It's not like the switch from aluminum to copper, which is a 2x resistivity
improvement.
You just can't beat plain old copper.
73
H.
NQ5H

"Roy Lewallen" wrote in message
...
I've seen real-life cases with high-Q microstrip structures where gold
plating actually caused a significant lowering of efficiency. As you
point out, nickel is used as a barrier metal to prevent alloying of the
gold with the underlying copper. If the gold isn't at least several skin
depths thick, significant current flows in the nickel. Nickel is a
particularly poor RF conductor, very much worse than copper, because the
skin depth in nickel is decreased dramatically by its ferromagnetic
permeability. So, if you're able to calculate skin depth, and know what
you're doing, and are willing to use quite a bit of gold (particularly
necessary at HF and below) you can achieve efficiency with gold plating
that's pretty much indistinguishable from that of copper. If you don't
know what you're doing, it is possible to substantially degrade the
efficiency by gold plating. I'm sure somebody could be conned into
buying one, though.

Roy Lewallen, W7EL

Gary V. Deutschmann, Sr. wrote:

Hi Gang

Since the radiation of an antenna is done primarily on the surface of
the elements (or wire) would gold plating the elements increase the
efficiency of the antenna in any way?

Gold sounds expensive, but if thin enough, one ounce of gold could
plate an entire football field. Brass corrods, nickel is usually used
as the first plating before another metal like gold is plated over
that. If the cost for gold over the cost of brass is only about 1
buck per foot of element length, making cost not relavent to the
question. Would a gold plated antenna work better than aluminum or
nickel plated?

TTUL
Gary

silver is a better conductor than gold, but will tarnish very easily, might
now be a good idea for what you are intending

just my two cents


"H. Adam Stevens, NQ5H" wrote in message
...
Hi Roy;
It's worse than that: Copper will diffuse throught the gold and pile up on
the surface.
I showed that with an Auger microprobe at Motorola decades ago.
So to go to a gold surface, nickel is mandatory, then a thick gold
coating;
Too expensive!
It's not like the switch from aluminum to copper, which is a 2x
resistivity
improvement.
You just can't beat plain old copper.
73
H.
NQ5H

"Roy Lewallen" wrote in message
...
I've seen real-life cases with high-Q microstrip structures where gold
plating actually caused a significant lowering of efficiency. As you
point out, nickel is used as a barrier metal to prevent alloying of the
gold with the underlying copper. If the gold isn't at least several skin
depths thick, significant current flows in the nickel. Nickel is a
particularly poor RF conductor, very much worse than copper, because the
skin depth in nickel is decreased dramatically by its ferromagnetic
permeability. So, if you're able to calculate skin depth, and know what
you're doing, and are willing to use quite a bit of gold (particularly
necessary at HF and below) you can achieve efficiency with gold plating
that's pretty much indistinguishable from that of copper. If you don't
know what you're doing, it is possible to substantially degrade the
efficiency by gold plating. I'm sure somebody could be conned into
buying one, though.

Roy Lewallen, W7EL

Gary V. Deutschmann, Sr. wrote:

Hi Gang

Since the radiation of an antenna is done primarily on the surface of
the elements (or wire) would gold plating the elements increase the
efficiency of the antenna in any way?

Gold sounds expensive, but if thin enough, one ounce of gold could
plate an entire football field. Brass corrods, nickel is usually used
as the first plating before another metal like gold is plated over
that. If the cost for gold over the cost of brass is only about 1
buck per foot of element length, making cost not relavent to the
question. Would a gold plated antenna work better than aluminum or
nickel plated?

TTUL
Gary

"S" wrote in message
et...
silver is a better conductor than gold, but will tarnish very easily,
might
now be a good idea for what you are intending

I thought that silver oxide was a decent conductor, which is why it is
sometimes used as a plateing material.

jim
N8EE

On Fri, 16 Apr 2004 20:40:53 -0400, "JLB"
wrote:


"S" wrote in message
. net...
silver is a better conductor than gold, but will tarnish very easily,
might
now be a good idea for what you are intending

I thought that silver oxide was a decent conductor, which is why it is
sometimes used as a plateing material.

Hi All,

It hardly matters unless you are speaking of switch contacts.
Insulated wire's insulation is absolutely unconductive, and yet in the
context of antennas it doesn't impact the wire's capacity to carry
current.

Oxidation products only become a problem at interfaces where they
either resist current between the joined conductors, or create a
semiconducting barrier.

The technician is taught to clean surfaces of tarnish to bring bright
metal into contact. Then crimp them (or twist the wire - same thing)
for a gas tight seal. Then solder them to weather proof the seal
(solder is never meant to be a mechanical join or the conductive
path). Common practice allows for solder to provide more
functionality than what I describe - this does not elevate the method.
Barring the final solder, switch contact faces must meet the same
conditions of bright metal and gas tight seals. This is often
achieved by pressure (some mistake the so-called "wiping" action as
meaning to scrub the oxide away - a useful metaphor but only that;
otherwise switches would self demolish in very few operations) and a
sustaining current (wet vs. dry contacts).

73's
Richard Clark, KB7QHC

What about silver plated RF connectors?

As far as that goes, there are also plenty of gold plated connectors out
there.

Jim
N8EE

"Richard Clark" wrote in message
news
On Fri, 16 Apr 2004 20:40:53 -0400, "JLB"
wrote:


"S" wrote in message
. net...
silver is a better conductor than gold, but will tarnish very easily,
might
now be a good idea for what you are intending

I thought that silver oxide was a decent conductor, which is why it is
sometimes used as a plateing material.

Hi All,

It hardly matters unless you are speaking of switch contacts.
Insulated wire's insulation is absolutely unconductive, and yet in the
context of antennas it doesn't impact the wire's capacity to carry
current.

Oxidation products only become a problem at interfaces where they
either resist current between the joined conductors, or create a
semiconducting barrier.

The technician is taught to clean surfaces of tarnish to bring bright
metal into contact. Then crimp them (or twist the wire - same thing)
for a gas tight seal. Then solder them to weather proof the seal
(solder is never meant to be a mechanical join or the conductive
path). Common practice allows for solder to provide more
functionality than what I describe - this does not elevate the method.
Barring the final solder, switch contact faces must meet the same
conditions of bright metal and gas tight seals. This is often
achieved by pressure (some mistake the so-called "wiping" action as
meaning to scrub the oxide away - a useful metaphor but only that;
otherwise switches would self demolish in very few operations) and a
sustaining current (wet vs. dry contacts).

73's
Richard Clark, KB7QHC

On Sat, 17 Apr 2004 21:45:46 -0400, "JLB"
wrote:
What about silver plated RF connectors?

As far as that goes, there are also plenty of gold plated connectors out
there.

Hi Jim,

What about them indeed? If they don't meet the requirements of bright
untarnished metal, then they need pressure mating (all the good ones I
know specify this - but deeply embedded within their core
manufacturing specs) e.g. Amp RF connectors:
"Insufficient contact force will give rise to metal to oxide
junctions. The classic rectifiers were metal oxide by
composition.

"The applied mounting force is concentrated in the surface area of
the protrusion which, on engagement with the panel, punctures the
existing oxide layer to give a metal-to-metal, gas-tight
junction."

The gold plating, presumably, precludes giving rise to oxidation
products; however, pressure then becomes an issue of mating surface
area (Ohms). Every precision contact used for Resistance and Voltage
standards (in the old days) were tapered brass plugs that could be
wedged into the jack with a twist (pressure). They knew about gold
then too, but brass served admirably.

73's
Richard Clark, KB7QHC

Hmmm...My book says aluminum's resistivity is about 2.6 microohm-cm,
and copper's is 1.7, only a 1.5:1 ratio--though it may not be quite
that good for commonly used aluminum alloys. OTOH, copper also
suffers from being alloyed. But in any event, it's good to keep in
mind that the RF resistance ratio for non-magnetic materials goes as
the square root of the bulk resistivity ratio, because higher
resistivity materials have larger skin depth. So a 2:1 ratio at DC
ends up being only 1.41:1 at RF, and 1.5:1 at DC is only a bit over
1.2:1 at RF.

Since both copper and aluminum have good conductivity, it's just not
worth sweating in practically all cases, unless the antenna is very
short (and thus has very low feedpoint radiation resistance).

Actually, what I thought Gary might be getting at is the protection
from corrosion that gold might offer, as compared with bare copper.
I'd say that it IS worth worrying about protecting your antenna from
corrosion. Maybe you just have to think about it long enough to
understand that you are lucky to live in a place where corrosion isn't
a problem, or maybe you live next to the ocean where salt spray will
get the best of almost anything metallic. But like Roy says, gold
over nickel is probably a bad idea. Unplated stainless steel antenna
wire is probably a bad idea. Painted copper pipe, or anodized
aluminum tubing, will probably work well for a long time.

Cheers,
Tom


"H. Adam Stevens, NQ5H" wrote in message ...
Hi Roy;
It's worse than that: Copper will diffuse throught the gold and pile up on
the surface.
I showed that with an Auger microprobe at Motorola decades ago.
So to go to a gold surface, nickel is mandatory, then a thick gold coating;
Too expensive!
It's not like the switch from aluminum to copper, which is a 2x resistivity
improvement.
You just can't beat plain old copper.
73
H.
NQ5H

One place where I can clearly see the difference between copper and aluminum
is comparing my (copper) Nott screwdriver with my (aluminum) Tarheel
screwdriver or my (aluminum) Hi-Q mobile antenna on 20 meters.
Mounted on my Durango, at resonance the Nott's impedance is 9 ohms, while
the Tarheel is 20 ohms and the (smaller tube) Hi-Q is 30 ohms; Measured with
the same whip in all cases.
This is a case of a short antenna.
The difference is significant and easily measured.
73
H.
NQ5H

"Tom Bruhns" wrote in message
m...
Hmmm...My book says aluminum's resistivity is about 2.6 microohm-cm,
and copper's is 1.7, only a 1.5:1 ratio--though it may not be quite
that good for commonly used aluminum alloys. OTOH, copper also
suffers from being alloyed. But in any event, it's good to keep in
mind that the RF resistance ratio for non-magnetic materials goes as
the square root of the bulk resistivity ratio, because higher
resistivity materials have larger skin depth. So a 2:1 ratio at DC
ends up being only 1.41:1 at RF, and 1.5:1 at DC is only a bit over
1.2:1 at RF.

Since both copper and aluminum have good conductivity, it's just not
worth sweating in practically all cases, unless the antenna is very
short (and thus has very low feedpoint radiation resistance).

Actually, what I thought Gary might be getting at is the protection
from corrosion that gold might offer, as compared with bare copper.
I'd say that it IS worth worrying about protecting your antenna from
corrosion. Maybe you just have to think about it long enough to
understand that you are lucky to live in a place where corrosion isn't
a problem, or maybe you live next to the ocean where salt spray will
get the best of almost anything metallic. But like Roy says, gold
over nickel is probably a bad idea. Unplated stainless steel antenna
wire is probably a bad idea. Painted copper pipe, or anodized
aluminum tubing, will probably work well for a long time.

Cheers,
Tom


"H. Adam Stevens, NQ5H" wrote in message
...
Hi Roy;
It's worse than that: Copper will diffuse throught the gold and pile up
on
the surface.
I showed that with an Auger microprobe at Motorola decades ago.
So to go to a gold surface, nickel is mandatory, then a thick gold
coating;
Too expensive!
It's not like the switch from aluminum to copper, which is a 2x
resistivity
improvement.
You just can't beat plain old copper.
73
H.
NQ5H

That's much, much more difference than can be explained by the different
conductivities of the metals. Either some very resistive alloys are
involved, or there are differences between the antennas other than the
type of metal.

Roy Lewallen, W7EL

H. Adam Stevens, NQ5H wrote:
One place where I can clearly see the difference between copper and aluminum
is comparing my (copper) Nott screwdriver with my (aluminum) Tarheel
screwdriver or my (aluminum) Hi-Q mobile antenna on 20 meters.
Mounted on my Durango, at resonance the Nott's impedance is 9 ohms, while
the Tarheel is 20 ohms and the (smaller tube) Hi-Q is 30 ohms; Measured with
the same whip in all cases.
This is a case of a short antenna.
The difference is significant and easily measured.
73
H.
NQ5H