I used some old coax to connect up arial I had put up to have TV in the workshop. But the signal strength was very low. I eventually discovered the
screen was open circuit due to corrosion. The screen was brittle and covered with white powder which I assumed was CuCl perhaps caused by
environmental HCl or the PVC insulation.
Today I was making up some flying lead using thick twin core speaker cable. The copper coloured multi strand conductors were covered with white
corrosion. While stripping off the insulation I discovered the conductors were copper clad aluminium. I now suspect the white powder is aluminium
oxide/hydroxide probably caused by moisture attacking the incoherent copper plating.
I bet the problem with the coax was because the screen was copper clad aluminium. I replaced the coax with new coax . Still got signal strength
problems when it rains because the line of sight to the transmitter is through the tops of trees. I need a taller mast or switch to sat receiver.
I did not realise how much copper has been replaced by aluminium wires or even steel. I have several USB leads that are attracted to magnets which
probably means the conductors contain steel.
I guess the high price of copper has forced the change.
So if your having difficulty soldering some wire check it not very thin copper clad aluminum. paulll - 8-10-2021 at 11:24
Is the powder (somewhat) consistent along the length of the cable? They often put talc in them to aid flexibility.
CCA
MadHatter - 8-10-2021 at 12:24
Copper Clad Aluminum
It's been used for "cheap" jumper cables and the fact that it
resists "knotting" up when rolling it up. As for 75-ohm coaxial
cable, it is copper plated onto a steel wire. Any magnet tells me
that.
I sympathize with you about TV reception being hindered or
outright blocked by trees, buildings etc.. A higher reception point
is an absolute must. I live in the boondocks here in Maine but I
get very good reception over the air.
The coaxial I run to the outdoor antenna is RG-11 not the RG6
or RG59. RG-11 has a solid copper core, which though expensive
reduces signal loss. It's twice as thick as RG6 so compression
connectors are supplied on both ends. 50' cost me $34.95 through
AntennasDirect at the time. This would be cost prohibitive for a
cable company but reasonable for the rest of us.
My jumper cables are 20' 4-gauge copper wire. Again expensive but
does a much better job than any CCA.
[Edited on 2021/10/8 by MadHatter]Twospoons - 8-10-2021 at 12:59
The coaxial I run to the outdoor antenna is RG-11 not the RG6
or RG59. RG-11 has a solid copper core, which though expensive
reduces signal loss.
[Edited on 2021/10/8 by MadHatter]
Solid copper will make little difference at RF frequencies, because the skin effect results in the current being carried at the surface of the
conductor. At 100MHz most of the current is carried in the top 10um.
Low loss coax uses larger diameter conductors to get more surface area, along with lower loss dielectrics, such as PTFE or foamed PE.
Conductor Diameter
MadHatter - 8-10-2021 at 18:47
RG-6 is AWG 18(.0403") diameter. RG-11 is AWG 14(.0641")
diameter. Approximately 59% increase in surface area. Where I
live I need all the help I can get. The attenuation differences get
wider at the higher frequencies as you've pointed out. wg48temp9 - 8-10-2021 at 23:12
Is the powder (somewhat) consistent along the length of the cable? They often put talc in them to aid flexibility.
I only samples three points near one end of the speaker cable. the corrosion was greatest at the end.
The coax was initially sample several times over about two meters at one end. The outer insulation sheath of that part looked weathered judging from
surface color and texture. The corrosion of the screen was about the same and so intense that the screen wire would brake as the sheath was striped.
The white(more accurately off white) powder was about the same over the two meters. I then checked about half way along the 20m length coax the
corrosion was less intense with much less powder. At that point I decided to replace the coax. The powder had a granular look not like talcum
powder.
On a different subject I was told that two houses in the high point of neighborhood have previously been struck by lightning even though there are
several of tall trees in the neighbourhood. So I will earth the mast and add lightning arrester to the coax. I don't want all my electronics fried.
Line of sight
Yes If I could get the aerial sufficiently high. Unfortunately there is a rail and a road embankment between my arial and the transmitter. The sides
of both are covered with tall trees. The top of my 10 meter mast, actually a two meter pole attached to an 8 metre pine tree stump, is only about two
or three meters above the embankment so the trees some vehicles and trains block LOS to the transmitter. I guess surreptitious use of a chainsaw
would solve the problem of the trees LOL. That happened in the local park and it upset a lot of people.Fulmen - 8-10-2021 at 23:31
Trees die all the time, especially if they are fed Roundup. rockyit98 - 9-10-2021 at 06:15
coper plated steel is fine because at transmitting frequencies most current pass within copper outer skin due to skin effect. thin wires of Al coated
copper is the worst since galvanic corrosion makes otherwise good conductor(Al) waste away if not coated with enamel (Magnet wire).
thin mesh of steel is used to shield cables from interference, that's why some USB cables tend to stick to magnets even conductors are copper.wg48temp9 - 9-10-2021 at 08:26
I found the crappy coax so I stripped of the outer sheath and took some pics.
This is the stripped coax showing the broken shielding strands.
You can see white corrosion products in the inside of the sheath and some of powder on the blue paper.
A close up of the wire from the shield. The powder is more easily seen.
I dropped some of the shield wire in some sodium hydroxide solution I was using to clean a stainless steel beaker of some tarry gung, thats the black
bits. The white area is the foaming as the wire dissolves. Given this is TV coax, that strongly suggests its copper clad aluminum wire.
[Edited on 10/9/2021 by wg48temp9]macckone - 12-10-2021 at 08:02
copper coated aluminum wire is evil.
coax that is outdoor rated (type-f I think), is going to be much more resistant to this kind of thing and is much more likely to be solid copper. The
price will reflect that.
There is also double insulated coax for use on poles, it has an outer braid of steel so it can be put under tension. The steel has some kind of epoxy
coating and an outer sheathing.
riser, plenum and indoor rated coax should not be exposed to the elements.
The difference between plenum, riser and indoor is fire rating.
None of them are 'water resistant'.
