No question about that. My 6M antenna is at the other end of 350 ft of
LDF5-50, 0.9 dB loss. It's a SteppIR, so I also use it for legal limit
on the HF bands. So my preamp is in the shack. If it was practical for
me to install a dedicated 6M antenna at 120 ft (which is where the
SteppIR is), I would. But it isn't practical.
It's important to realize that every engineering problem is different,
most solutions are compromises, and which set of compromises are best
for any given situation depend on many factors. In this case, real
estate, the cost of another tower, somewhere to put another tower, the
hard line that I can scrounge used at a good price, etc. And yes, I'd
love the extra 2-3 dB that a better 6M antenna would provide.
73, Jim K9YC
On Wed,1/25/2017 4:54 PM, Ken Arck wrote:
So if you place a preamp with a NF of .5 dB at the "rig end" of a
feedline run that exhibits 3 dB of loss at the frequency involved, you
now have an effective noise figure of 3.5 dB ahead of your receiver.
Placing the preamp at the antenna has an obvious advantage of reducing
that NF by 3 dB.
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