[600MRG] Coax shielding effectiveness

[Gedas]

Something I should have included along with that particular URL. In case 
you are not sure how to work with numbers for transfer impedance's etc 
there is an approximation (in this case based on a 50-ohm system) that 
will equate Zt to SE:

SE = 20Log [2x50/Zt]

so for FSJ1-50 at around 1/2 MHz the SE = ~88 dB

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 2:28 PM, Gedas wrote:
>
> See if this will get you started.
>
> http://www.repeater-builder.com/antenna/andrew/andrew-shielding-effectiveness.pdf
>
> Gedas, W8BYA
>
> Gallery athttp://w8bya.com
> Light travels faster than sound....
> This is why some people appear bright until you hear them speak.
> On 12/9/2019 2:23 PM, david vanhorn wrote:
>> I knew fsj1-50 would be good but I haven't found data from anyone at 
>> these low frequencies. Any pointers would help.
>>
>> On Mon, Dec 9, 2019, 12:14 PM Gedas <w8bya at mchsi.com 
>> <mailto:w8bya at mchsi.com>> wrote:
>>
>>     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 athttp://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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>
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