As the reigning Low Power USA DX Contester(currently) in many of the popular
DX contests, I think I can speak with some experience on this subject. One
year - I think it was 2009 - I was sick and knew I wouldn't be competitive
for an ARRL DX contest. I decided to try an experiment. 160 was not in
great shape and 10M was having those "noise floor" big EU stations and
that's it conditions. I called stations using 100W in the contest (although
the max limit is 150W). I could work some with difficulty but not many -
typical of those conditions with low power in this contest. I remember
multiple multiple times that at 100W they would CQ in my face. At 150W you
would start getting the "?" and at 200W I MADE about 50% of those Qs. I
might have been able to get through with the 150W (~1.8dB increase) of power
with a lot of trying.
Bottom line, while 1dB in and of itself is admittedly not material. 2 and 3
dB for sure are material in DXing and Contesting where the path is right on
the edge of being made in HF. And the 1dB is quickly passed with the wrong
coax on top of bandpass filters and antennas.
Here at my QTH, I have my towers up on a ridge behind the house. Its 250ft
of coax from the back of the rig to the 2 x 8 switch at the base of Tower 1.
130 ft from there to the base of Tower 2. And my top 10M antenna at 80 ft
is on top of Tower 2. That's about 450ft of coax from rig to 10M antenna.
I run LDF5-50A to the 2x8 and from Tower 1 to Tower 2 and LMR600 to stack
match on 10 at 50 ft. The last 50ft of coax to the antenna is LMR400. The
total loss to that antenna is about 1.6dB. If the whole run was LMR400 it
would be about 4dB. That 2.4dB power loss is the equivalent of doubling the
size of the antenna roughly and clearly would affect weak signal work based
on my tests.
Ed N1UR
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