Re: [IRCA] AC twin lead or speaker wire for lead in.

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

> There was an article foating around called something like, Is Your lead
> in a snake? There were experiments about grounding the coax.

This was simply laid on the ground in a fairly straight line.  Nothing
buried.  I tried ground each end separately, and both ends.  Nada..  I could
try grounding every 50 feet, as the coax is that length with barrel
connectors.  It'd be easy to ground.  I'll grab some ground rods next time
I'm past Home Depot or Lowe's.

I have 300' of the Radio Shack coax.  What I may try is to run two 150'
lengths side by side and set them up as a balanced line.  I may even be able
to twist them together.  That way I can see what the leakage is, and if
grounding the shields at either end or both ends has any effect.  I should
make up a balun for that.  The resultant impedence would probably be 200
ohms.  A 2:1 turns ratio balun would be appropriate.

> By your experiments Craig, it sounds like the coax is an issue. Now,
> why doesn't coax going to an FM or TV antenna affect the
> directivity? Or does it?

I have no idea if it does, or why.  I would think that it does not and I
have no clue as to why.  Again, should be easy to test.  I can just lay out
the coax, terminate it with the dummy load and tune through the FM band with
the Blaupunkt in the truck.

Another thing I tried is winding a dozen turns of RG-58 through an FT-290-75
toroid core to make a choke.  Made no difference, grounded or not.

> We all know that coax is good for shelding against noise, but the
> thought of the coax even with matching transformers affecting the
> pattern is for concern. I wonder if there is any coax out there that
> would  work. It sounds like the general run of the mill coax is suspect.
> I still like using coax as it is good against water and noise. Hardline?
> I wonder what would be the best.

Dallas Lankford apparently also uses shielded twinax.  This cable was used
extensively in older IBM servers instead of ethernet cable.  I had a client
with an AS400 IBM maybe 15 or 20 years ago.  That stuff was really expensive
and not all that easy to use.  It was about the diameter of RG8 and required
special connectors.  IIRC, the R390A used one of those connectors on the
back for the balanced input.

>    In my daytime tests of checking the R8 with coax from in the house
> and out in the back running the antennas directly into the receiver, I
> did not find any difference as far as I could tell. Nothing "jumped" out
> at me. So I wonder in reality, if the difference is in what type of an
> antenna is used, loop vs beverager vs EWE.? The load might make a
> difference too. Any thoughts?

There are a mess of things that don't make sense to me, not the least of
which is why the input leakage happens in a shielded line in the first
place.  That's one reason I've tossed this out here.  To see what others
have found, if they've been down the same path.

Craig Healy
Providence, RI

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