Difference between Isolation

HI,

i would like to know isolation rule thumb for double shielded cable and single
for let say 1GHz with RG59 ...


Thx
David

Thickness of the shield plays an important role in shielding, but the most important role for an effective EM shielding is the number of shields.
When the transmitted wave goes through the material, from the first shield to the second shield, the magnetic field is attenuated due to the absorption loss between shields. So, the field lose energy when try to penetrate the second field, resulting a reflection, and just a small percent of the field penetrates the second shield.

I can see what you are getting at, but I have never ever seen any spec for this, I think its actually quoted the opposite way around i.e. radiation losses. Some cables are made deliberately leaky to radiate RF so they can have a defined field strength over a narrow field. i.e. trying to get broadcast reception down a tunnel. solid screen the best, then tape, then braiding. I would do a comparative test, 1m of each cable type (X number of manufacturers) RF signal generator, 50 ohm termination, and some sort of receiver.
Frank

I don't think is any coax cable which was made deliberately to have poor shielding. Or, not this was the target of the manufacturer. Poor coax shields are just cheaper.

Vfone please read this :- http://www.solwise.co.uk/downloads/f...troduction.pdf and or look ay Wikipedia.
Frank

yeah but thats a VERY specialist use of a specific type of cable. For the other 99% of any other standard coax cable, purposeful leakage isnt planned.

Personally I have never seen any isolation charachteristics for standard cables. And if most major RF installations are anything to go by, then the systems designers and installers are not particularly worried either

cheers
Dave

So guys
i understand that numbers that i am looking for, depend on a lot of parameters...
but do somebody can give me some number!? close (+/- 10dB) something...?

David

The semi-rigid cable isolation is about 70dB, and the SMA is also about the same data.

What the difference between semi rigid and semi flex?

Semi rigid has better isoaltion effect than semi flex, but is harder to shape. What is your isolation requirments?