Topband: Silent Feedline for RX antennas

[Doug Waller]

Gentlemen:

It is generally accepted that low gain receive antenna coax lead-ins, from
Beverages to Flags, must be well shielded, balanced and choked, to prevent
unwanted signals and noise from entering the system & degrading performance.
To this end, I have ordered several FT-150A-F toroids and mini-coax to make
3-K-ohm chokes.  I also plan to ground the coax between the new rotary Flag
and receiver, to drain the shield-received RF.  A dozen long, snap-on split
ferrites will be installed along the way.

Suddenly a light:  Why not use two RG-58's or 59's in balanced feedline
configuration, twisted 2-3 times per inch, to eliminate all the above?  The
shields at the feedpoint would be bonded, but left floating.  The unchoked
RF received equally by the outside of the shields (due to twist) would
induce equal currents onto the two center conductors, which would then
cancel.  Transformers on both ends of the dual feedlines would match the
doubled feedline impedance, while providing more common mode protection.
One coax ground near the receiver should suffice.

I wish this feedline to be as silent & balanced as possible, as an
experimental -56dbi gain RX antenna will be tried on down the road.

My run is only 100 feet, so I could see a longer run of dual coaxes
eventually surpassing the costs of choking and grounding.  But I could buy
alot of RG-58 for the price of the three FT-150A-F's & spool of mini-coax.
If you have already done this, or have comments, please let me hear.

73/DX, Doug / NX4D