"Critical" coupling is a coupling that achieves that which is desired in the
application involved.
Thus "critical" coupling varies dependent on the situation or application
involved which in your
'specific ' application may well be defined as you stated but is not all
inclusive..
That's how I see it and what I spoke of is confirmed by NEC and by personal
experimentation
If you choose to disagree that is your choice but goes directly to my
statement regarding quoting
of text without full understanding.
I have no interest in argueing the fact, try somebody else.
Art

"Richard Harrison" wrote in message
...
Art Unwin wroyte:
"Then the book is incorrect assuming you are using statements
correctly."

I included page numbers to make it easy to check the accuracy of my
translation.

Art said elements are "critically coupled". Critical coupling is defined
as maximum energy transfer at the resonant frequency.

Coupling additions (more loads) to a feedpoint lowers the impedance
unless additional measures (transformations) are taken. Coupling more
loads to a feedpoint is tantamount to paralleling resistors. Terman is
right.

Best regards, Richard Harrison, kB5WZI

I wrote:
"Critical coupling is defined as maximum energy transfer at the resonant
frequency."

Also:
"Coupling additions (more loads) to a feedpoint lowers the impedance
unless additional measures (transformations) are taken."

I`ve since consulted Terman, and critical coupling is defined as I said
above. Terman adds coupled elements differently than I did above.

On page 64 of his 1955 edition, Terman defines critical coupling as:
"These trends continue as the coefficient of coupling is increased until
the coupling is such that the resistance which the secondary circuit
couples into the primary at resonance is equal to the primary
resistance. This is called the CRITICAL COUPLING and causes the
secondary current to have the maximum value it can attain."

On page 65, Terman`s statement supports Art:
"When the coupled impedance is added to the self-impedance of the
primary circuit, the effect at resonance is to increase the effective
primary resistance above the value that would exist in the absence of
the secondary. This causes the primary current at resonance to be
reduced in all cases by the presence of the secondary."

I wrongly assumed a coupled load would add to the primary current. I
apologize to Art and to others who I misled.

Best regards, Richard Harrison, KB5WZI

Richard,
It was ten years ago that this subject came up and which I used as a basis
for
parallel circuit antennas versus series type antennas. It also led to the
use of
circuitry analysis (complex circuitry) to provide for lossless feed systems
and
cluster coupled antennas.
All of the above was ridiculed by the experts over the years because of my
use of element coupling terminology, such that what it
pertained to was never taken seriously and sometimes mocked.
What is more frausterating to me is that many commercial antennas still
pursue
gain to the extent that low impedance occurs and where the purchaser is
forced
to purchase loss generating matching systems which robs him of some of the
purchased gain. Force1 even notes in their literature that manufactures are
supplying
poor matching impedances in the search of financial competitive gain
YOU are the first expert on this newsgroup to take a step back and pursued
a
rethink of this subject and supplied your findings in a posting.
Possibly some will now subject you to ridicule or,
if your enunciation of Terman is convincing enough, will say they knew it
all the
time but preferred to pursue harassement.
I thank you from the bottom of my heart for your courage shown in your last
posting
and hopefully, others will build on, or pursue the implications/contents of
your posting.
Best regards
Art KB9MZ Xg

"Richard Harrison" wrote in message
...
I wrote:
"Critical coupling is defined as maximum energy transfer at the resonant
frequency."

Also:
"Coupling additions (more loads) to a feedpoint lowers the impedance
unless additional measures (transformations) are taken."

I`ve since consulted Terman, and critical coupling is defined as I said
above. Terman adds coupled elements differently than I did above.

On page 64 of his 1955 edition, Terman defines critical coupling as:
"These trends continue as the coefficient of coupling is increased until
the coupling is such that the resistance which the secondary circuit
couples into the primary at resonance is equal to the primary
resistance. This is called the CRITICAL COUPLING and causes the
secondary current to have the maximum value it can attain."

On page 65, Terman`s statement supports Art:
"When the coupled impedance is added to the self-impedance of the
primary circuit, the effect at resonance is to increase the effective
primary resistance above the value that would exist in the absence of
the secondary. This causes the primary current at resonance to be
reduced in all cases by the presence of the secondary."

I wrongly assumed a coupled load would add to the primary current. I
apologize to Art and to others who I misled.

Best regards, Richard Harrison, KB5WZI

Art Unwin wrote:
"My ARRL books go back a decade or more and the graphs showing the gain
per boom length has several curves based on different measurements
e.t.c."

I haven`t encountered similar curves based on NEC, but I`ve found thye
old ARRL curves on page 163 of my 1970 edition of the "A.R.R.L. Antenna
Book" (cover price=$2.50).

Variation between curves from 3 different groups of observers are within
"1 S-unit" (6 dB). Gain ranges from a minimum of about 7 dB for a Yagi
with a 1/2-wave boom length (pessimistic) to a 19 dB gain for a
6.5-wavelength boom length (optimistic).

The optimistic curve is labeled "Greenblum", and seems too good to be
true. The other two curves have flattened out as the number of
wavelengths increases. The Greenblum curve is almost a straight line. As
Kraus showed in his solution to the Deutsche Welle antenna gain problem,
you often need to double the total number of elements to get a 3 dB
antenna gain.

Best regards, Richard Harrison, KB5WZI

Richard, the more I study the boom length question the more I feel that the
ARRL
should drop the three curve gain/boom length graph. First there has to be a
condition that all elements are on the same plane. The other condition must
be
that all the elements are straight and parallel. The more I study the two
element
antenna I find that changing the added element height relative to one
another ,
even if a small distance , can change the gain.
I understand that there are "Landorfer ?"curved elements that can also
increase the gain.
I also proved that by NEC.
If one allows elements numbers to be added to increase ad hoc then NEC shows
that a quasi dish shape will occur
where the focus can stay equal to .1 wavelength and where gain increases to
over 14 dbi.
If one takes a further step by "shaping "the elements whether it be the feed
element or the
reflective elements then not only does the beam width narrow with increased
gain but the
TAO decreases about one degree which is a huge advantage when using small
garden type antennas.
Based on the above findings it would be impossible to generate a NEC curve
that would make sense
unless the above two conditions are set in place for the average amateur.
The latter would give
some protection against fraudulent vendors and supply a datum curve that is
meaningful to all.
I do believe that this posting should put an end to this thread and I thank
you again for your input.
Regards
Art



"Richard Harrison" wrote in message
...
Art Unwin wrote:
"My ARRL books go back a decade or more and the graphs showing the gain
per boom length has several curves based on different measurements
e.t.c."

I haven`t encountered similar curves based on NEC, but I`ve found thye
old ARRL curves on page 163 of my 1970 edition of the "A.R.R.L. Antenna
Book" (cover price=$2.50).

Variation between curves from 3 different groups of observers are within
"1 S-unit" (6 dB). Gain ranges from a minimum of about 7 dB for a Yagi
with a 1/2-wave boom length (pessimistic) to a 19 dB gain for a
6.5-wavelength boom length (optimistic).

The optimistic curve is labeled "Greenblum", and seems too good to be
true. The other two curves have flattened out as the number of
wavelengths increases. The Greenblum curve is almost a straight line. As
Kraus showed in his solution to the Deutsche Welle antenna gain problem,
you often need to double the total number of elements to get a 3 dB
antenna gain.

Best regards, Richard Harrison, KB5WZI

Art Unwin wrote:
"I do believe that this posting should put an end to this thread and I
thank you again for your input."

All the questions answered? Any topic is eventually tiresome, but not
everyone tires of it at the same time. Gain per unit length is likely
not a straight line at any particular frequency. There is probably much
more to be said about best coupling for maximum gain.

There was an article by Joe Reisert, W1JR in the December 1986 issue of
"Ham Radio" about a 28-element, 21-foot boom, 432 MHz (about 70 cm WL)
Yagi Joe built. The gain was about 19 dBi, or about 0.9 dB per foot at
432 MHz.

The pattern shown and gain are said to come from MININEC.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:


There was an article by Joe Reisert, W1JR in the December 1986 issue of
"Ham Radio" about a 28-element, 21-foot boom, 432 MHz (about 70 cm WL)
Yagi Joe built. The gain was about 19 dBi, or about 0.9 dB per foot at
432 MHz.

The pattern shown and gain are said to come from MININEC.

Best regards, Richard Harrison, KB5WZI


That was a 24 foot (7.3 wavelength) antenna, with 19.15 dBi claimed,
which was actually higher than newer modeling programs give it.

tom
K0TAR

Richard Harrison wrote:


There was an article by Joe Reisert, W1JR in the December 1986 issue of
"Ham Radio" about a 28-element, 21-foot boom, 432 MHz (about 70 cm WL)
Yagi Joe built. The gain was about 19 dBi, or about 0.9 dB per foot at
432 MHz.

The pattern shown and gain are said to come from MININEC.

Best regards, Richard Harrison, KB5WZI


Oops, my mistake, 10.5 wavelengths, and about .9 dB under what it could
be, assuming the model is correct for mininec.

tom
K0TAR

There is probably much
more to be said about best coupling for maximum gain.

Maximum Gain, that seems to be all people think about.

Max. Gain is not always a good thing.

Example which is better for 2 meter mobile a 1/4 wave 0 dB whip a 3 dB 5/8
wave or a 6 dB collinear ?

A true 6 dB collinear makes a very poor mobile antenna.
Unless your parked on level ground, then it works fine.

The 3 dB 5/8 wave works good if you are on fairly flat terrain.
But get into the mountains or use repeaters that are on
10,000 ft. + mountains like we have here in WY and Colorado.
A 0 dB 1/4 wave whip can some times work better.

People put a 3 dB gain mag mount on the back corner of the
finder, setting at a 30 degree angle and wonder why it don't work as well as my
0 dB 1/4 wave mounted in the center of the roof of a van. (Mounted in a hole
in the roof, not a mag mount.)

All I am saying is there is more to an antenna than Max gain.
What about bandwidth, pattern etc.

There, I feel better.

73 Al Lowe N0IMW
Arrow Antenna

"N0IMW" wrote in message
...
There is probably much
more to be said about best coupling for maximum gain.

Maximum Gain, that seems to be all people think about.

Max. Gain is not always a good thing.

Example which is better for 2 meter mobile a 1/4 wave 0 dB whip a 3 dB
5/8
wave or a 6 dB collinear ?

A true 6 dB collinear makes a very poor mobile antenna.
Unless your parked on level ground, then it works fine.

The 3 dB 5/8 wave works good if you are on fairly flat terrain.
But get into the mountains or use repeaters that are on
10,000 ft. + mountains like we have here in WY and Colorado.
A 0 dB 1/4 wave whip can some times work better.

People put a 3 dB gain mag mount on the back corner of the
finder, setting at a 30 degree angle and wonder why it don't work as well
as my
0 dB 1/4 wave mounted in the center of the roof of a van. (Mounted in a
hole
in the roof, not a mag mount.)

All I am saying is there is more to an antenna than Max gain.
What about bandwidth, pattern etc.

There, I feel better.

73 Al Lowe N0IMW
Arrow Antenna

Son, you forgot "loss".
When I drilled that hole in the middle of the roof of the brand new Durango,
I married that truck.
Then there are the two BIG holes, one in each rear quarterpanel.
At 90,000 miles I'm about to do the FIRST brake job; It's an OK truck.
Anyone remember how Chrysler's still in business?
Anyway, here's my rig:

Comet 144/222/440 on an NMO mount topside center, small Hi-Q screwdriver 5'
above ground on the left rear quarterpanel.
Tarheel 4' screwdriver 4' above ground with a 4' whip on the right rear
quarter panel, toroidal transformer matched for 20 ohms.
For 160/80 I also have a BIG Hi-Q for the right side.
Rigs are Kenwood: 742 and 480HX.
No tuners.

73
H., NQ5H