One point eight dee bee

[alorona]

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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[alorona]

I forgot to say one thing. I'll try to say it quickly.

This might help those of us that are still skeptical about hearing a 1.8 dB change.

Forget about the cost of doing this for the moment; I'm only talking about the effort right now.

If you knew for a fact that you had a 1.8 dB loss somewhere in your shack that could be reduced to 0 dB just by replacing or changing something, would you do it? Or would you say, "Naw, they can't hear 1.8 dB anyway, so I won't bother. I'll just leave the loss in the system."

If you answered the latter, then I have a followup question: If you knew for a fact that you had two separate and unrelated things, each of which had a 1.8 dB loss, would you leave them as is, or replace them?

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[daleputnam]

a viable question posed... very good...

 I would do all I could to reduce that loss... the first time... and upon discovering the second, do all necessary to reduce that one too. With a consideration as to the cost involved.

For example.. with my wire antennas.. I have introduced a noticable amount of loss... as compared to a beam antenna... and a beam antenna at 50 foot... is noticably worse than a beam at 100 - 200 - 300 foot. However... there is a consideration with logic applied to correct that what we can.. and do the best we can with what we can't change....

I can't change locations, add 300 to 400 foot antenna, but I can replace a poor connector in the shack. It works... what is also fun... is finding new ways to improve a signal path.. through the atmosphere, and all the way in through the rx.. into my ear... and reverse the path... all the way to the other ears.

  Merry Christmas, to all,

--... ..---

Dale - WC7S in Wy


 
     
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[AC7AC]

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