How many hams find a feedline length of 100 Meters acceptable? Lets look at
a more realistic length of 100 feet and the loss is less than 2 dB at 30
Mhz. The loss is much less on the lower bands. With all due respect, your
example sucks!

"Owen Duffy" wrote in message
...
On Mon, 07 Nov 2005 23:26:47 GMT, Cecil Moore wrote:


Yes, and with a reasonable limit, the SWR on the ladder-line
doesn't matter. IMO, 25:1 is no problem for ladder-line.

There must be a host of unstated assumptions behind that statement to
make it valid in a limited scenario.

Using TLDETAILS to work up a load of 16+j0 on 100m of Wireman551
ladder-line at 30MHz, the predicted VSWR varies between 25 at the load
end and a very modest 6.5 at the generator end, yet the predicted loss
is around 6dB. Some might not find that an acceptable loss.

Owen
--

On Mon, 7 Nov 2005 22:21:35 -0500, "Fred W4JLE"
wrote:

How many hams find a feedline length of 100 Meters acceptable? Lets look at
a more realistic length of 100 feet and the loss is less than 2 dB at 30
Mhz. The loss is much less on the lower bands. With all due respect, your
example sucks!

BTW, I make your example 2.7dB, not less than 2dB. (Perhaps you labour
under the misaprehension that loss per unit length is a constant in
this situation).

Fred, what you have highlighted is the unstated assumption of some
limit on length. You know enough to choose a length so that the ROT is
true, but does a learner soaking this up know as much?

Owen
--

I choose a ladderline length to always feed the antenna at a current node.

"Owen Duffy" wrote in message
...
On Mon, 7 Nov 2005 22:21:35 -0500, "Fred W4JLE"
wrote:

How many hams find a feedline length of 100 Meters acceptable? Lets look
at
a more realistic length of 100 feet and the loss is less than 2 dB at 30
Mhz. The loss is much less on the lower bands. With all due respect, your
example sucks!

BTW, I make your example 2.7dB, not less than 2dB. (Perhaps you labour
under the misaprehension that loss per unit length is a constant in
this situation).

Fred, what you have highlighted is the unstated assumption of some
limit on length. You know enough to choose a length so that the ROT is
true, but does a learner soaking this up know as much?

Owen
--

Fred W4JLE wrote:
I choose a ladderline length to always feed the antenna at a current node.

And because a current node is guaranteed to occur at least
every 1/2WL, an HF feedline need never be longer than 164
feet, Owen's 100 meter feedline notwithstanding. :-)
--
73, Cecil http://www.qsl.net/w5dxp

On Tue, 8 Nov 2005 13:23:46 -0500, "Fred W4JLE"
wrote:

I choose a ladderline length to always feed the antenna at a current node.


I don't know what this really means, and how it is relevant to the
discussion that the ROT in question doesn't hold true for longer feed
line lengths.

You have previously dismissed 100m of feed line with the eloquent
"sucks" comment, whatever that means.

What has feeding an antenna at the current node got to do with feed
line length? Is it intended to imply that feed line length or the ROT
are not relevant when you feed the antenna at a current node?

Is it just a trite comment to consume bandwidth?

Owen

"Owen Duffy" wrote in message
.. .
On Mon, 7 Nov 2005 22:21:35 -0500, "Fred W4JLE"
wrote:

How many hams find a feedline length of 100 Meters acceptable? Lets look
at
a more realistic length of 100 feet and the loss is less than 2 dB at 30
Mhz. The loss is much less on the lower bands. With all due respect, your
example sucks!

BTW, I make your example 2.7dB, not less than 2dB. (Perhaps you labour
under the misaprehension that loss per unit length is a constant in
this situation).

Fred, what you have highlighted is the unstated assumption of some
limit on length. You know enough to choose a length so that the ROT is
true, but does a learner soaking this up know as much?

--

Owen Duffy wrote:
What has feeding an antenna at the current node got to do with feed
line length?

Feedline length for an average system may be about 75 ft.,
the distance from the antenna to the transceiver. If a
current maximum point occurs at 87 ft., make the feedline
87 ft. long with (usually) no tuner required.

I assume what Fred thinks sucks is your implication that the
average ham feeds his antenna with 100 meters of feedline.
What percentage of hams do you think actually use 100 meters
of transmission line?
--
73, Cecil http://www.qsl.net/w5dxp

On Wed, 09 Nov 2005 15:02:35 GMT, Cecil Moore wrote:

Owen Duffy wrote:
What has feeding an antenna at the current node got to do with feed
line length?

Feedline length for an average system may be about 75 ft.,
the distance from the antenna to the transceiver. If a
current maximum point occurs at 87 ft., make the feedline
87 ft. long with (usually) no tuner required.

Well, I guess you are guessing at what Fred meant. But such a current
maximum on the feed point repeats every electrical half wave, and such
an approach doesn't preclude using feed lines much longer than 75
feet.


I assume what Fred thinks sucks is your implication that the
average ham feeds his antenna with 100 meters of feedline.

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.

Thing is, about averages, is that the detail you throw away to
calculate the average may have been relevant. Further, there is little
consolation to the guy who has 10dB worse than average performance
because he has used longer feed line under your ROT, to know that a
whole lot of guys using shorter feed line are enjoying better than
average performance and on average, it all balances out.

It is quite feasible to place an antenna at longer distances if you
want, but ladder line should be operated at lower VSWR for acceptable
losses, or better feed line used... and the ROT doesn't say that.

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.

What is an "average ham" now days? Is it one that doesn't have a real
interest in the technical side of the hobby, the "I just wanna talk on
the radio" set... they like ROTs, gives them something to parrot on
air.

Owen
--

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

Hardly trite, it limits the line length to a maximum of 164 feet.

"Owen Duffy" wrote in message
...
On Tue, 8 Nov 2005 13:23:46 -0500, "Fred W4JLE"
wrote:

I choose a ladderline length to always feed the antenna at a current
node.


I don't know what this really means, and how it is relevant to the
discussion that the ROT in question doesn't hold true for longer feed
line lengths.

You have previously dismissed 100m of feed line with the eloquent
"sucks" comment, whatever that means.

What has feeding an antenna at the current node got to do with feed
line length? Is it intended to imply that feed line length or the ROT
are not relevant when you feed the antenna at a current node?

Is it just a trite comment to consume bandwidth?

Owen

"Owen Duffy" wrote in message
.. .
On Mon, 7 Nov 2005 22:21:35 -0500, "Fred W4JLE"
wrote:

How many hams find a feedline length of 100 Meters acceptable? Lets
look
at
a more realistic length of 100 feet and the loss is less than 2 dB at
30
Mhz. The loss is much less on the lower bands. With all due respect,
your
example sucks!

BTW, I make your example 2.7dB, not less than 2dB. (Perhaps you labour
under the misaprehension that loss per unit length is a constant in
this situation).

Fred, what you have highlighted is the unstated assumption of some
limit on length. You know enough to choose a length so that the ROT is
true, but does a learner soaking this up know as much?

--