Got a Radio Works choke balun I'd like to use for feeding ladderline
out of an unbalanced tuner.


I'm sure others here will correct me if I'm wrong, but I believe that
what you want to do is a very bad idea. Baluns are not meant to operate
under the potential very high SWR conditions you are likely to have on the
output of your tuner. Damage to the balun is likely. Besides, what is the
point of a balun on your tuner's output if you are using ladderline,
anyway?


Ed K7AAT

Ed wrote:

Got a Radio Works choke balun I'd like to use for feeding ladderline
out of an unbalanced tuner.

I'm sure others here will correct me if I'm wrong, but I believe that
what you want to do is a very bad idea. Baluns are not meant to operate
under the potential very high SWR conditions ...

It depends on whether the very high SWR is on the ladder-line
side or on the coax side. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote in
. net:

Ed wrote:

Got a Radio Works choke balun I'd like to use for feeding ladderline
out of an unbalanced tuner.

I'm sure others here will correct me if I'm wrong, but I believe
that
what you want to do is a very bad idea. Baluns are not meant to
operate under the potential very high SWR conditions ...

It depends on whether the very high SWR is on the ladder-line
side or on the coax side. :-)


Well, he said "OUT of an unbalanced tuner" so I assume that's the
ladderline side.

Ed K7AAT

Ed wrote:
Cecil Moore wrote:
It depends on whether the very high SWR is on the ladder-line
side or on the coax side. :-)

Well, he said "OUT of an unbalanced tuner" so I assume that's the
ladderline side.

Yes, and with a reasonable limit, the SWR on the ladder-line
doesn't matter. IMO, 25:1 is no problem for ladder-line.
--
73, Cecil http://www.qsl.net/w5dxp

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
--

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
--

Well, he said "OUT of an unbalanced tuner" so I assume that's the
ladderline side.

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


Correct, a high SWR is not an issue for ladderline, but the guy was
wanting to stick an apparently 50 ohm coax balun right there in between
his balanced tuner output and that ladder line. I would think a high
SWR, with some TX power, in that device might not do it much good.


Ed