Just for the record, 150 watts is actually closer to 1.8 dB over 100 watts. But
regardless, it is interesting to consider what it would take to realize this
increase on 160 meters.
The movers and shakers on this reflector have eloquently made the case that 1.8
dB really does make a difference at the other end of your transmitted signal. A
few hours ago I would have poo-poohed this, but who am I to disagree with
the folks that really know? I'm now convinced, so let's proceed on the
assumption that 1.8 dB is not only audible, but worth the effort.
I started thinking about where the typical ham could pick up 1.8 dB of extra CW
transmit signal strength on 160. By "typical"-- and I may be using the wrong
word here-- I mean the ham on an average city lot, surrounded by neighbors,
power lines, and at least somewhat mindful of aesthetics.
a. An antenna with 1.8 dB greater directivity in the direction desired.
b. 1.8 dB less antenna feedline loss.
c. 1.8 dB more power.
Let's take these one at a time.
a. According to my definition of 'typical' above, our ham doesn't have the
luxury of putting up very effective 160 m transmtting antennas. A vertical may
be out of the question due to the danger of falling into power lines. He very
likely is using something like an inverted L with a few radials that can be
placed on a small lot, or maybe even a sloper. Given the space constraints,
what could he possibly do to gain 1.8 dB? Very likely nothing-- not rearranging
the antenna, nor increasing it's size, nor increasing the ground system. He
can't increase the size of the antenna any more because of obstructions and
neighbors, nor can he lay down more radials due to driveways, patios, and
garages. If he is using a horizontal antenna (dipole, loop, etc.) then he
should try to go to a vertical of some sort like an inverted L. That may give
him 1.8 dB or more right there.
There have been some replies to the effect that arrays, Beverages, and other
arrangements can achieve the desired increase, but of course these are all out
of the question for the city lot-confined ham.
b. If our ham is feeding an antenna with RG-8 grade coax, his matched feedline
attenuation is around 0.26 dB / 100 feet at 1.8 MHz (ARRL Antenna Book, 17th
edition, p. 24-16). Unless his run is 700 feet -- unlikely on a city lot-- he
is not going to realize 1.8 dB of gain just by changing his feedline, even if
he goes to open-wire ("600 ohm") type line.
(If the SWR on the line is high then there may be some action he could take to
find a better place to feed the antenna that gives him a better match, in order
to reduce the mismatched line loss, and so a benefit would be seen at a line
length less that 700 feet. 700 feet in the previous example was considering
matched line loss only.)
c. That leaves increasing power output as his only probable recourse.
Note that I *assumed* at the outset that it was *worth* the financial
investment if 1.8 dB could be found somewhere. Of late there have been many
comments about whether it is worth the money to invest into a particular
station upgrade. But how do you place a price on 1.8 dB when your options are
extremely limited? Still, each ham must decide whether it's worth the money,
even if it is the only option when it comes to squeezing every available dB out
of a station.
Thank you for tolerating this long post. Don't forget to cut it way down if you
reply.
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