In the ARRL Antenna Handbook it discusses feeding the Lazy H
antenna. The handbook states; "Matching stubs are recommended in
cases where a non-resonant line is to be used". Is the handbook
referring to coax verses ladder line, is it referring to a resonant
length of ladder line verses a non resonant length of ladder line, it
is referring to ladder line with an antenna tuner at the transmitter
verses ladder line without an antenna tuner? In any case I'm not sure
what they are specifically referring to. Clarification requested
please.

Thank you,

Michael Rawls
KS4HY

On Jun 11, 7:55*am, Michael wrote:
* Clarification requested please.

They are probably worried about losses if there is a high SWR on the
coax feedline. I don't see any reason why the Lazy-H can't be fed with
ladder-line and Z0-matched to 50 ohms at the tuner which will cause a
near conjugate match at the antenna feedpoint and throughout the rest
of the system using low-loss feedline.
--
73, Cecil, w5dxp.com

"Michael" ha scritto nel messaggio
...
In the ARRL Antenna Handbook it discusses feeding the Lazy H
antenna. The handbook states; "Matching stubs are recommended in
cases where a non-resonant line is to be used". Is the handbook
referring to coax verses ladder line, is it referring to a resonant
length of ladder line verses a non resonant length of ladder line, it
is referring to ladder line with an antenna tuner at the transmitter
verses ladder line without an antenna tuner? In any case I'm not sure
what they are specifically referring to. Clarification requested
please.

Thank you,

Michael Rawls
KS4HY

A possible explanation is the following one.

If you use an appropriate matching stub at the antenna, the antenna impedance
can be made equal to the ladder line characteristic impedance. In such (matched)
condition, the impedance seen by the transmitter is independent of the ladder
line length. You will most likely need a tuner at the transmitter to adapt that
impedance to the 50-ohm transmitter impedance.

On the contrary, not using any stub, the antenna impedance will most likely be
different from the ladder line characteristic impedance. In such (unmatched)
condition the impedance seen by the transmitter varies with the ladder line
length. Trimming that length, you may obtain an impedance close enough to 50
ohm, so avoiding the need for a tuner (although a balun will stiil be needed).

73

Tony I0JX
Rome, Italy

On Jun 11, 5:55*am, Michael wrote:
* In the ARRL Antenna Handbook it discusses feeding the Lazy H
antenna. * The handbook states; "Matching stubs are recommended in
cases where a non-resonant line is to be used". * Is the handbook
referring to coax verses ladder line, is it referring to a resonant
length of ladder line verses a non resonant length of ladder line, it
is referring to ladder line with an antenna tuner at the transmitter
verses ladder line without an antenna tuner? *In any case I'm not sure
what they are specifically referring to. *Clarification requested
please.

Thank you,

Michael Rawls
KS4HY

Seems like it would be helpful if the handbook gave you an accurate
definition of what they mean by "stub" and "resonant" versus "non-
resonant" line. To me, a "stub" means a length of transmission line
attached to a feed system (perhaps at the antenna feedpoint, but
perhaps instead attached to the through-line feeding the antenna at
some point away from the antenna feed point), which is open or shorted
at the free end. (It's also possible to have a stub that's tuned by
putting a [variable] capacitance across the free end--or an
inductance.) That is, a "stub" is NOT a piece of transmission line in
series with the feed line (which makes it a part of the feed line).
If you have a piece of transmission line feeding the antenna whose job
it also is to transform an impedance, it _might_ be called "resonant,"
though I would much prefer the term "series matching section" of
line. That's because, in general, the length might not be an integer
number of electrical quarter waves. The series section might be used
to tune out reactance as well as transform the resistive part of the
impedance.

So my suspicion is that they are using "resonant line" to mean a
"series matching section," where the series matching section is
(probably) an odd number of quarter waves long, to help match between
two different resistive impedances. The ideal impedance of that
series section would be the square root of the product of the two
impedances (resistances) you want to match between.

I use a program called "winSMITH" which I love because it lets me very
quickly see what pretty much any arbitrary "ladder" arrangement of
line sections (series and stub)--as well as lumped reactances--will do
to transform any arbitrary impedance. The graphical representation
gives me insight into what's going on, and how I can adjust things to
get the best match. Though I especially like some of the features of
this program, there are other Smith chart programs that will give you
similar insights. Several of these programs are free. It takes a bit
of playing with them to understand what's going on, but I think it's
well worth the time because of the deeper understanding you'll get
from them. "YMMV" as they say; if graphs don't do anything for you, a
Smith chart probably won't either.

Cheers,
Tom