That's a good one Larry. Never thought about flexible conduit before. I'm
not familiar with the specific conduit you're talking about, but if it's
like Greenfield conduit, the only possible problem I could see with it is
the same problem with braided grounding straps or metallic roof gutters.
That is if it becomes corroded, it can act as an Intermod (IMD) generator.
This is called the "Rusty Bolt Effect". If it gets bad enough it can cause
TVI/RFI and be difficult to locate. At the very least it can raise your
noise floor making your shack "RF Deaf".
At commercial RF sites it becomes more critical to reduce these IMD sources
since there is much more RF on site than at a ham shack, but it might not
hurt to avoid creating future problems now while you have the chance.
Here's a list of site environmental requirements from Motorola's R56 (c)
site standards:
Locations that can mix signals and create IMD:
* Rust on anything, but especially in metal-to-metal contact.
* Braided wires or straps. 1000's of possible PN junctions.
* Loose metal to metal connections. All should be rigid.
* Fencing -Chain link should be vinyl clad if possible.
* Dissimilar metals -Can cause accelerated Galvanic corrosion.
* Unjacketed transmission lines (like hard line cables)
* Bare metallic cable ties.
As long as you're using it indoors, and if it's installed correctly and not
allowed to corrode, you should not have any problems. It would be a
judgement call whether or not to use it and how much. With these facts in
mind you can probably make the correct decision for your situation. Good
Luck & Happy Holidays!
73,
de ed -K0iL
> -----Original Message-----
> From: Larry Kozal [SMTP:woowly@home.com]
> Am hoping for input from the gang - experience and/or theory - Am debating
> best method of running 50' of AC to basement shack at new QTH, possible
> RFI
> generation/pickup in mind.
>
> 1- Run regular Romex type wire
> 2- Hang EMT conduit
> 3- Run Flex conduit
>
> The Flex is appealing because I can run it through holes in the joists -
> question is if the long metal to metal joint along the spiraled
> construction
> of flex is going to create RFI (even though it's a continous piece of
> metal,
> is there a potential across the seam?)
>
> What about coupling joints in EMT?
>
> Thinking too much?
>
> Thanks,
> Larry Kozal K8PUJ
>
>
>
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