"ml" wrote in message
...
hi

I've seen recently that some companies such as andrews etc are now
offering different coax and hardline with al outer shielding

they advertise lower cost, and lighter weight then copper , ok i get
that

but then they say the rf spec's are 'the same' so i ponder how do they
do that i would think copper would have better spec's ? obviously i
am missing something obvious

I think you are referring to the Times Microwave LMR cables. The LMR240 is
sort of a low loss RG8X, and the LMR400 is a low loss RG213. These cables
are made like RG6 in that there is 100% foil coverage bonded to the inner
dielectric with normally a tinned copper braid over it. The aluminum
versions of these replace the copper braid with aluminum braid. They claim
the loss is the same because the bonded foil is the same. The only problem I
see is soldering to the aluminum braid, and I suspect crimp on connectors
will be easier to install. You can still solder the center conductor. Check
out
www.timesmicrowave.com
BTW, the LMR240UF makes for great patch cords. It has a stranded center
conductor. 1/4 inch cable that is rated at 1500W. The LMR240 without the UF
suffix has a solid center conductor, costs about half as much, and I use it
for longer runs below 30 MHz. Haven't seen any of the aluminum stuff yet.

Tam/WB2TT

"Tam/WB2TT" wrote in
:

BTW, the LMR240UF makes for great patch cords. It has a stranded
center conductor. 1/4 inch cable that is rated at 1500W. The LMR240

From the spec sheet, the average power rating at 30MHz is 1240W. I assume
that is with VSWR=1, so that a further derating is required for mismatch.
For example, at VSWR=2, the heating at a current maximum is nearly double
that for a flat line, so the power rating might be more like 620W with
VSWR=2.

Of course, in SSB telephony, the average power is very low and the cable is
probably limited by voltage breakdown at peaks, specified as 5.6kW for
LMR240UF.

Owen

"Owen Duffy" wrote in message
...
"Tam/WB2TT" wrote in
:

BTW, the LMR240UF makes for great patch cords. It has a stranded
center conductor. 1/4 inch cable that is rated at 1500W. The LMR240

From the spec sheet, the average power rating at 30MHz is 1240W. I assume
that is with VSWR=1, so that a further derating is required for mismatch.
For example, at VSWR=2, the heating at a current maximum is nearly double
that for a flat line, so the power rating might be more like 620W with
VSWR=2.

Of course, in SSB telephony, the average power is very low and the cable
is
probably limited by voltage breakdown at peaks, specified as 5.6kW for
LMR240UF.

Owen
Something happened to my cut and paste. The 1500W was supposed to refer to
the non UF.

Tam/WB2TT

"Tam/WB2TT" wrote in message
. ..

"Owen Duffy" wrote in message
...
"Tam/WB2TT" wrote in
:

BTW, the LMR240UF makes for great patch cords. It has a stranded
center conductor. 1/4 inch cable that is rated at 1500W. The LMR240

From the spec sheet, the average power rating at 30MHz is 1240W. I assume
that is with VSWR=1, so that a further derating is required for mismatch.
For example, at VSWR=2, the heating at a current maximum is nearly double
that for a flat line, so the power rating might be more like 620W with
VSWR=2.

Of course, in SSB telephony, the average power is very low and the cable
is
probably limited by voltage breakdown at peaks, specified as 5.6kW for
LMR240UF.

Owen
Something happened to my cut and paste. The 1500W was supposed to refer to
the non UF.

Tam/WB2TT

Found some Tables of loss and power handling for various cables. At 30 MHz:

LMR240 has a max power of 1490W, compared to RG213 of 1800W.
LMR240 has a loss of 1.3 DB, compared to RG213 of 1.2 DB.
Not a whole lot of difference, but the 213 has about 3X the cross section
area. The LMR240 has 90 DB shielding, the 213 is not specified.

I assume that these were specified under the same conditions. It is
interesting that at 900 MHz, the LMR240 has less loss than RG213. Compared
to RG8X, the 240 has 4 times the power handling capacity.

Tam