> By far the most practical approach is the tuner in the shack. It's what I
> have and I've never bothered with measuring
> or calculating the loss from the tuner in the shack approach as it's not
> going to change.
That's practical if the shack is located against an exterior wall. Open
transmission line easily cross couples with Ethernet cabling and household
SMPS devices. A balanced line easily keeps its balance on transmit so long
as the conductors do not couple to nearby objects. But on receive, it's a
different story. It's rare for a noise source to balance evenly onto the
conductors. Invariably, the line will become perpendicular to a source at
various points. So, multiple noise sources from within the home can make a
balanced line seem rather unbalanced. The wider the line spacing, the lower
the line loss -- but susceptibility to noise sources will increase. It does
not take much imbalance to produce noisy results on receive.
For me, the most practical approach was to locate the tuning function in a
Wx-proof enclosure, located as close as possible to the load, yet still have
access to it for maintenance purposes. About 60 ft. of 600-ohm line is used
between the ATU and a 135 ft. dipole at 55 above ground. A 50 ft run of
LMR-400 is used between the shack and ATU. Of course, that solution
requires some means of remote-controlling the C and L components. Practical
for some, but not for all.
Paul, W9AC
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