[600MRG] Coax shielding effectiveness

[Gedas]

Hi Dave. Funny you should ask. I am right in the middle of making a 
video where I test about 10 different (and common) coaxial cables 
specifically for their SE. The project is on and off as I just have too 
many pokers in the fire right now.

It is not as simple as one may think to measure the SE accurately esp if 
the cable is of high quality and has a high SE. If I were still employed 
and had access to my old lab and shielded enclosures and able to 
generate & measure known RF fields from DC to daylight it would be a 
much, much easier task. Having to do it in my basement lab makes it a 
much more challenging project. In the end I chose to arrive at the SE by 
measuring the cross-talk between two identical coax cables.

My methodology is to lay two identical cables of equal length next to 
each other on a plywood table. Both far ends of the coax cables are 
terminated in 50 ohm loads. One cable is driven with a tracking 
generator (then broadband power amplifier) while the other coax fed into 
the input of my spectrum analyzer. The amount of cross-talk between the 
two cables can then be used to directly see what the SE was. It gets 
hairy if the cables have a high SE as the SA has a limited sensitivity 
(NF) and I can only generate several watts of broadband RF from DC to 
about 1 GHz.

Until that video is done you will have to go by OEM data. FSJ1-50 will 
have an extremely high SE (well over 100 dB). If you need some help 
looking up the exact OEM data just hollar. 73

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 12/9/2019 1:37 PM, david vanhorn wrote:
> I've been searching around without much success.
> I'm trying to find data sheets or good measurements of shielding 
> effectiveness of the various coax types, including FSJ1-50 for this 
> band.  I'm not seeing anything talking much below 100MHz.
>
> Can someone point me in the right direction?
>
> -- 
> K1FZY (WA4TPW) SK  9/29/37-4/13/15
>
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