Owen Duffy wrote:
The loss scale is in dB, it is the loss in dB at position x metres
from the load.

Aha, I see that noted at the bottom now that I scroll down.
It didn't make sense to me if the loss scale was in percent.
So what do I get if I integrate the area under the curve?

Incidentally, I was engaging in fuzzy republican thinking when
I came up with eleven current maximum points in 100 meters of
feedline. Of course, there are twice that, i.e. 22 current maximum
points which can be counted on your graph.

You could calculate an average loss per meter figure, but I don't know
what you could you use it for? The fact that this line is not straight
(as some people seem to assume) means that working with average
numbers is inherently inaccurate.

Owen, most hams are not rocket scientists like you :-) Quite
often, a rule-of-thumb average beats total ignorance. All
measurements contain errors and are inherently inaccurate.
Some of us live with that reality. Some of us rant and rave
about it. Next time you are on your motorcycle, note that
your speedometer is "inherently inaccurate" as is your gas
gauge as are your reflexes. If you are not inherently inaccurate
throwing darts in the local pub, you are a very unusual homo sapien.

I, for one, am satisfied with average losses, presumably averaged
over one half wavelength. The way I came up with that 25:1 limit
on my open-wire SWR is that 600/25 equals 24 ohms and that is an
acceptable impedance to my IC-256PRO's autotuner. Noting that the
losses in 100 ft. of open-wire line running at an SWR of 25:1 are
acceptable was an afterthought.
--
73, Cecil http://www.qsl.net/w5dxp

Owen Duffy wrote:
Well, I guess you are guessing at what Fred meant.

Nope, not a guess. Fred and I are on the same wavelength. :-)
We use the same "notuner" method for resonating our antenna
systems.

That is his misinterpretation if that is the case. I did not say an
"average ham", but I assert that it is not all that uncommon to have a
ham antenna located at 100m or more, and the ROT falls down.

But it is indeed extremely uncommon for an *American* amateur
radio operator to have a feedline that is 100m long. I personally
know of only a handfull of cases in my 55 years of hamming and
most of those involved getting vhf/uhf antennas to the top of a hill.

Thing is, about averages, is that the detail you throw away to
calculate the average may have been relevant.

It may be relevant to a "rocket scientist", such as yourself, and
completely irrelevant and indeed beyond the understanding of the
average ham who must necessarily rely upon rules of thumb.

It is quite feasible to place an antenna at longer distances if you
want, ...

~99.99% of hams don't want to. Why make things more difficult?

It is the unstated length assumption (of apparently 75') of your ROT
that makes limits its validity to the people who are most likely to
lap it up.

Sorry to disagree, the great majority of "people who are most likely
to lap it up" are people with 60-100 foot feedlines. Most assertions
on this newsgroup are in the context of the average ham.

Owen, it's obvious that you deliberately picked 100 meters to try to
prove a point that you couldn't make otherwise. You chose an inferior
ladder-line that I wouldn't even allow on my property. Your attempts to
save face by dragging the discussion down some primrose path involving
minute details is interesting but not interesting enough to follow
you down said path.
--
73, Cecil http://www.qsl.net/w5dxp

On Thu, 10 Nov 2005 00:08:51 GMT, Cecil Moore wrote:


Owen, it's obvious that you deliberately picked 100 meters to try to
prove a point that you couldn't make otherwise. You chose an inferior
ladder-line that I wouldn't even allow on my property. Your attempts to
save face by dragging the discussion down some primrose path involving
minute details is interesting but not interesting enough to follow
you down said path.

I chose 100m as a round number that is practical and long enough to
demonstrate that at very high VSWR, the approximations that might hold
for shorter lengths and lower VSWR are no longer valid. Open wire
feeders well in excess of 100m are practical, but ladder line with
very high VSWR isn't.

(On the other hand, your 75' "standard" is about enough to reach the
feed point of a medium height antenna directly above the shack, and
might be argued as a minimum practical length for a good antenna.)

The ladder line I chose was one of the four that have reasonably good
characterisation (by N7WS) and it wouldn't matter much which of the
four you chose, they are fairly similar... I chose the first one on
the list. (The last one on the list, 554 with 25:1 load SWR give 5.6dB
against 6dB or 551... I wont bother checking the others.) No, I did
not deliberately choose an inferior ladder line.

Owen
--

Owen Duffy wrote:
I chose 100m as a round number that is practical ...

328.1 feet is NOT a round number. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Owen Duffy wrote:


(On the other hand, your 75' "standard" is about enough to reach the
feed point of a medium height antenna directly above the shack, and
might be argued as a minimum practical length for a good antenna.)

As opposed to the standard full height backyard antenna with 100 meter
feedline which would then be something more like this:

http://www.kkn.net/gallery/hcjb/hc15

;-)
ac6xg