Buck wrote:
Cecil Moore wrote:
Please explain your antenna and radio. I am assuming you have a solid
state rig with an so-239 connector on it for the basic and then you do
what?

Hi Buck, Please check out my associated web page and then
ask me anything that you don't understand.

http://www.w5dxp.com/notuner.htm

Contrary to what you may have been told, you can change
the 50 ohm SWR seen by your transmitter by changing the
length of the 450 ohm ladder-line.
--
73, Cecil http://www.w5dxp.com

An understanding of "mismatch loss" doesn't require SWR, reflections,
power waves, "reflected power", "reflected energy", or other real or
imagined complexities other than simple impedances. Here's what it means:

If you have a generator with a fixed output impedance such as a signal
generator, and connect it to a conjugately matched load, the power
dissipated in that load is the most you can get in any load connected to
the generator. For example, if your generator produces 10 volts RMS open
circuit and has a 50 ohm resistive output impedance, it can deliver 0.5
watt to a 50 ohm resistive load. If you connect any other load impedance
to the generator, you'll get less power to the load. You can calculate
exactly how much with simple circuit theory.

"Mismatch loss" is simply a way of expressing the reduction in power you
get due to the load being mismatched, compared to how much you'd get
with a matched load. For example, if you connect a 100 ohm resistor to
the output of the generator, it would dissipate 0.44 watt instead of
0.5, so the mismatch loss is 10 log 0.5/0.44 = 0.51 dB(*). If you
connect a 25 ohm resistor to the output, you also get 0.44 watt in the
load resistor, again a "mismatch loss" of 0.51 dB. These numbers are
calculated using nothing more complicated than simple lumped circuit
principles.

Mismatch loss is a useful concept when connecting fixed-impedance
circuits together, such as in a laboratory environment. But it doesn't
apply to either antennas or to VSWR. All you have to do to reduce the
"mismatch loss" to zero is to insert a tuner or other matching network
between the generator and the load. Presto, the generator sees 50 ohms
resistive, the load dissipates 0.5 watt, and the mismatch loss is zero.

(*) For the 100 ohm example: The circuit consists of a 10 volt
generator, and a 50 ohm resistance (the generator impedance) and 100 ohm
resistance (the load) in series. So the current is V / R = 10 / (50 +
100) = 66.67 mA. The power dissipated in the load is I^2 * R = 0.06667^2
* 100 ~ 0.44 watt. No reflections, VSWR, transmission lines, or bouncing
power waves required.

Roy Lewallen, W7EL

billcalley wrote:
What I gleaned from the excellent answers for the original "VSWR
Doesn't Matter?" thread is that high VSWR doesn't really matter in a
lossless transmission line environment between a transmitter's antenna
tuner and the antenna, since any reflected RF energy will simply
continue to "bounce" back and forth between the tuner's output
impedance and the antenna's input impedance until it is, finally,
completely radiated from the antenna without loss.

But then why does the concept of "mismatch loss" exist in
reference to antennas? I have quickly calculated that if a
transmitter outputs 100 watts, and the TX antenna has an impedance
that will cause a VSWR of 10:1 -- using lossless transmission line --
that the mismatch loss in this "lossless" system would be 4.81dB!
(Reflected power 66.9 watts, RL -1.74).

Since mismatch loss is the "amount of power lost due to
reflection", and is as if an "attenuator with a value of the mismatch
loss where placed in series with the transmission line", then I would
think that VSWR would *definitely* matter, and not just for highly
lossy lines either. But here again, I'm probably not seeing the
entire picture here. What am I missing??

Confused!

-Bill

Roy Lewallen wrote:

An understanding of "mismatch loss" doesn't require SWR, reflections,
power waves, "reflected power", "reflected energy", or other real or
imagined complexities other than simple impedances. Here's what it means:

If you have a generator with a fixed output impedance such as a signal
generator, and connect it to a conjugately matched load, the power
dissipated in that load is the most you can get in any load connected to
the generator. For example, if your generator produces 10 volts RMS open
circuit and has a 50 ohm resistive output impedance, it can deliver 0.5
watt to a 50 ohm resistive load. If you connect any other load impedance
to the generator, you'll get less power to the load. You can calculate
exactly how much with simple circuit theory.

"Mismatch loss" is simply a way of expressing the reduction in power you
get due to the load being mismatched, compared to how much you'd get
with a matched load. For example, if you connect a 100 ohm resistor to
the output of the generator, it would dissipate 0.44 watt instead of
0.5, so the mismatch loss is 10 log 0.5/0.44 = 0.51 dB(*). If you
connect a 25 ohm resistor to the output, you also get 0.44 watt in the
load resistor, again a "mismatch loss" of 0.51 dB. These numbers are
calculated using nothing more complicated than simple lumped circuit
principles.

Mismatch loss is a useful concept when connecting fixed-impedance
circuits together, such as in a laboratory environment. But it doesn't
apply to either antennas or to VSWR. All you have to do to reduce the
"mismatch loss" to zero is to insert a tuner or other matching network
between the generator and the load. Presto, the generator sees 50 ohms
resistive, the load dissipates 0.5 watt, and the mismatch loss is zero.

Bravo. And a great deal simpler to understand than most handwaving on
these threads.

Roy Lewallen, W7EL

Best, Dan.

"Cecil Moore" wrote in message
. net...
bw wrote:
Entropy increases

Seems to me that evolution violates that principle.
--
73, Cecil http://www.w5dxp.com

Not to mention the Noble Prize Ilya Prigogine won for "Dissipative
Structures" in 1977.

Spontaneous Ordered Structures arising out of disorder. But it takes an
Energy Flow to produce them.

Robert

"Robert" wrote in message
link.net...

"Cecil Moore" wrote in message
. net...
bw wrote:
Entropy increases

Seems to me that evolution violates that principle.
--
73, Cecil http://www.w5dxp.com

Not to mention the Noble Prize Ilya Prigogine won for "Dissipative
Structures" in 1977.

Spontaneous Ordered Structures arising out of disorder. But it takes an
Energy Flow to produce them.

Robert

Sorry. Forgot to include the link.

http://en.wikipedia.org/wiki/Ilya_Prigogine

Robert

On Mar 29, 2:10 pm, "billcalley" wrote:
What I gleaned from the excellent answers for the original "VSWR
Doesn't Matter?" thread is that high VSWR doesn't really matter in a
lossless transmission line environment between a transmitter's antenna
tuner and the antenna, since any reflected RF energy will simply
continue to "bounce" back and forth between the tuner's output
impedance and the antenna's input impedance until it is, finally,
completely radiated from the antenna without loss.

There's also the case where a perfect VSWR does no good. That happens
when you connect a transmitter to an extremely lossy line and the
signal dissipates before it gets to the load :


But then why does the concept of "mismatch loss" exist in
reference to antennas? I have quickly calculated that if a
transmitter outputs 100 watts, and the TX antenna has an impedance
that will cause a VSWR of 10:1 -- using lossless transmission line --
that the mismatch loss in this "lossless" system would be 4.81dB!
(Reflected power 66.9 watts, RL -1.74).

Since mismatch loss is the "amount of power lost due to
reflection", and is as if an "attenuator with a value of the mismatch
loss where placed in series with the transmission line", then I would
think that VSWR would *definitely* matter, and not just for highly
lossy lines either. But here again, I'm probably not seeing the
entire picture here. What am I missing??

Confused!

-Bill

On Fri, 30 Mar 2007 02:43:38 GMT, Cecil Moore
wrote:

Buck wrote:
Cecil Moore wrote:
Please explain your antenna and radio. I am assuming you have a solid
state rig with an so-239 connector on it for the basic and then you do
what?

Hi Buck, Please check out my associated web page and then
ask me anything that you don't understand.

http://www.w5dxp.com/notuner.htm

Contrary to what you may have been told, you can change
the 50 ohm SWR seen by your transmitter by changing the
length of the 450 ohm ladder-line.

Ok, I have seen that. It isn't that the antenna isn't tuned, it is
tuned with the twin-lead instead of a conventional tuner.

I might have enough twin lead to build one of those. I'll have to
consider it. It has always tweaked my interest.

Thanks



--
73 for now
Buck, N4PGW
www.lumpuckeroo.com

Buck wrote:
Ok, I have seen that. It isn't that the antenna isn't tuned, it is
tuned with the twin-lead instead of a conventional tuner.

It has a tuned feeder instead of a conventional tuner.
--
73, Cecil http://www.w5dxp.com

On Fri, 30 Mar 2007 12:37:53 GMT, Cecil Moore
wrote:

Buck wrote:
Ok, I have seen that. It isn't that the antenna isn't tuned, it is
tuned with the twin-lead instead of a conventional tuner.

It has a tuned feeder instead of a conventional tuner.

I am curious to know, have you measured the power both at the antenna
and the radio to see what loss there might be? I wouldn't expect very
much, personally.

On a G5RV, it is taught that the twin-feedline is also part of the
antenna itself, is that true in your model as well?

thanks
Buck
--
73 for now
Buck, N4PGW
www.lumpuckeroo.com

http://www.w5dxp.com/notuner.htm

Cecil,

Looking more at your antenna, I am making several observations. I
posted the URL at the top for other readers to know what we are
talking about.

I kind of wish you would change the name of the antenna and not call
it 'no-tuner' because I feel let down every time I look at it and see
the feed-line tuner. I realize it isn't a conventional tuner. Don't
get me wrong, I think it is a GREAT idea and I like it very much and
would like to try it myself. However, I feel it is a little deceptive
in the name.

I have a few questions about the system. I may have asked some
already in another thread, so please bear with me. This is a better
place to discuss it rather than hijacking another thread.

I see you use 450 ohm ladder line (or window-line as some call it.) I
am wondering if the concept will also work with other impedance
feedline such as 600, 300 or 75 ohm twin-line or even possibly with
coax. ****


**** I just looked over your program. I see that you have it setup to
allow 300 or 450 ohm ladder line. I wonder if you have LLWL available
for 600 and 75 ohm.... I will try to put this in XL. (I don't have a
basic program.) OK, I just found the compiled program.

I am interested in making one, but I only have 300 ohm.

Does the feedline act as part of the antenna? I am sure it will, at
least up to the 'no-tuner' if it acts like a G5RV, but do you know if
the feedline radiates?

Have you measured the power at both sides of the 'no-tuner' to see
what loss there might be? I doubt there would be much considering
that you are using window-line.

I see a couple of the frequencies are above 1.5:1, which I am not
comfortable going over with solid state rigs. Do you think that could
be fine-tuned with the addition of a 1/2 foot section or maybe with
that and a 1/4 foot section?

Would it be safe to assume that I can create a mono-band dipole, maybe
even multi-band - if I am lucky, by fixing the length of the dipole
and the feedline such that the increment gives me the imax at the
balun for the desired frequency(s)?

Finally, you have a 1:1 choke at the feeder. I see that the better
quality coax, the more toroids are needed. Would there be a problem
with using a foot of RG-58 with the fewer toroids and then connect
that to the high-quality line? I suspect that by then the common-mode
currents will be gone and there would be minimum loss in such a short
strand of lower-grade coax for HF. I doubt there would be a
noticeable signal loss.

Does the 'no-tuner' feedline need to be spread out. I see from the
photo that your 16 foot section is one large loop, I figure it must be
close to a four-foot diameter loop.

Is there a similar system that would work with a vertical?

Thank you,

I appreciate your taking time to answer this. I hope many of us can
learn from it.

Buck
N4PGW








--
73 for now
Buck, N4PGW
www.lumpuckeroo.com