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
--

Owen Duffy wrote:
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.

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.
That's only 1/4 of an S-unit on the highest frequency HF band and less
on the other bands. That's perfectly acceptable to me and virtually
indistinguishable on an S-meter.

If you have to resort to 325 feet of ladder-line on 30 MHz to try
to prove me wrong, I feel really sorry for you. Why didn't you choose
a million feet to prove me even more wrong? 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'.
--
73, Cecil http://www.qsl.net/w5dxp

On Tue, 08 Nov 2005 02:09:13 GMT, Cecil Moore wrote:

Owen Duffy wrote:
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.

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. (The loss per meter is not a constant figure
in this situation.) Agreed, even that is not a large amount, and
indeed might be quite acceptable in many / most cases.

That's only 1/4 of an S-unit on the highest frequency HF band and less
on the other bands. That's perfectly acceptable to me and virtually
indistinguishable on an S-meter.

If you have to resort to 325 feet of ladder-line on 30 MHz to try
to prove me wrong, I feel really sorry for you. Why didn't you choose
a million feet to prove me even more wrong? 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.

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
--

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.

For example an SWR ratio of 10:1 using a hundred feet of RG-217 on
the 80-meter band is only about 1 dB loss. On 10-meters its a
different story.

I still subscribe to the belief that judging antenna performance based
solely upon SWR is like judging how well a automobile will perform
based solely on what the air pressure is in the tires.

Danny, K6MHE

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

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 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/

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.

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

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

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.