On Mon, 07 Nov 2005 19:16:08 -0800, Dan Richardson wrote:

On Tue, 08 Nov 2005 03:07:10 GMT, Owen Duffy wrote:

I often hear Rules of Thumb (ROT) like VSWR 3 is OK for coax and
25 if fine for open wire, or the converse... but something is lost in
the brief expression of those ROTs, and it seems more and more the
knowledge base of our hobby is the ROTs, rather than the underlying
principles. There is an appeal to the new experts in our hobby to
pickup the ROTs and parrot them... perhaps we need to take the time to
qualify what we say where learners are listening.

Owen

Owen,

The problem is that knowing the SWR is not worth much without knowing
the frequency and the spec's of the transmission line.

.... including the length. I agree fully.

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
--

Dan Richardson wrote -
The problem is that knowing the SWR is not worth much without
knowing
the frequency and the spec's of the transmission line.

==================================

The REAL problem is that very few people know the SWR on the
transmission line because the SWR meter doesn't measure it.

Aren't you are fooling yourselves?
----
Reg.

On Tue, 08 Nov 2005 03:40:33 GMT, Owen Duffy wrote:

On Mon, 07 Nov 2005 19:16:08 -0800, Dan Richardson wrote:

On Tue, 08 Nov 2005 03:07:10 GMT, Owen Duffy wrote:

I often hear Rules of Thumb (ROT) like VSWR 3 is OK for coax and
25 if fine for open wire, or the converse... but something is lost in
the brief expression of those ROTs, and it seems more and more the
knowledge base of our hobby is the ROTs, rather than the underlying
principles. There is an appeal to the new experts in our hobby to
pickup the ROTs and parrot them... perhaps we need to take the time to
qualify what we say where learners are listening.

Owen

Owen,

The problem is that knowing the SWR is not worth much without knowing
the frequency and the spec's of the transmission line.

... including the length. I agree fully.

Owen

Yep, I forgot to add that.

Thanks

Danny, K6MHE

email: k6mheatarrldotnet
http://www.k6mhe.com/

Owen Duffy wrote:
It appears that you are
lurking there in the down under outback just waiting for me to forget
to cross an 'i' or dot a 't'.

Cecil, people often employ long runs of open wire feed on HF (ie up to
30MHz), and it just shows that on longer runs, high VSWR can be an
issue for ladder line.

Guess I should have put a smiley face on my above posting.
Did you miss the humor?
--
73, Cecil http://www.qsl.net/w5dxp

Owen Duffy wrote:

Cecil Moore wrote:
If 100m (325 feet) of ladder-line results in 6dB loss, then a more
realistic 75 feet of ladder-line will result in about 1.4 dB of loss.

Close, I make it 2.2dB.

What matched line loss are you using? The wireman says that line
has about 0.2 dB of matched line loss per 100 ft at 30 MHz. According
to the chart in my ARRL Antenna Book, an SWR of 25:1 at the load
would cause about 1.5 dB loss in 75 feet.

... waiting for me to forget to cross an 'i' or dot a 't'.

Cecil, people often employ long runs of open wire feed on HF ...

Did you miss the humor?
--
73, Cecil http://www.qsl.net/w5dxp

Reg Edwards wrote:
The REAL problem is that very few people know the SWR on the
transmission line because the SWR meter doesn't measure it.

Aren't you are fooling yourselves?

A host of us use EZNEC and other modeling programs, like
you publish, to estimate the SWR and therefore the losses.
--
73, Cecil http://www.qsl.net/w5dxp

Guess I should have put a smiley face on my above posting.
Did you miss the humor?
===============================

Cec, even as a foreigner I seldom miss your humor, smileys or not.

Thank heavens, on the Internet, the English and American lanuages are
drawing closely together. But I am still inclined to draw a
distinction beween Americans and USA citizens. They are different!
---
Reg.

Reg Edwards wrote:
Thank heavens, on the Internet, the English and American lanuages are
drawing closely together. But I am still inclined to draw a
distinction beween Americans and USA citizens. They are different!

And Texans are even more so. Ours is the only state whose
flag is allowed to be flown at an equal height with the
US flag. (Some places around here fly the Texas flag an
inch or so higher than that damned Yankee flag. :-) Texas
was the only state having the legal right to seceed from
the USA during the Civil War. The last battle of the Civil
war was fought near Brownsville, TX and the South won.

Reg, I saw a program on "The Discovery Channel:
Ice Age Columbus: Who Were the First Americans?" It
said, based on the latest arrowhead and tool archaeological
evidence, that America was discovered by sea-going ice-age
Europeans 17,000 years before Columbus made his voyage. It
was asserted that some Native Americans still carry the
genetic markers donated by those early Europeans.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Reg Edwards wrote:

Thank heavens, on the Internet, the English and American lanuages are
drawing closely together. But I am still inclined to draw a
distinction beween Americans and USA citizens. They are different!


And Texans are even more so.

SNIPPED: That great ICON of America, John Wayne of Blessed Memory,
asserted that the residents of Texas were TEXICANS! [Not Americans and
NOT citizens of USA]. How does this impact citizenship??

Cecil, you opened a bag of Texas Nightcrawlers [Bass bait worms] with
your Texas comment. :-)

AK

Ours is the only state whose
flag is allowed to be flown at an equal height with the
US flag. (Some places around here fly the Texas flag an
inch or so higher than that damned Yankee flag. :-) Texas
was the only state having the legal right to seceed from
the USA during the Civil War. The last battle of the Civil
war was fought near Brownsville, TX and the South won.

Reg, I saw a program on "The Discovery Channel:
Ice Age Columbus: Who Were the First Americans?" It
said, based on the latest arrowhead and tool archaeological
evidence, that America was discovered by sea-going ice-age
Europeans 17,000 years before Columbus made his voyage. It
was asserted that some Native Americans still carry the
genetic markers donated by those early Europeans.