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What do the following things have in common: my multi-band dipole, my
dummy load, a toaster element, and a 100W lightbulb?

Answer: I can connect all three to my antenna tuner, get a reasonable
SWR match, and transmit into them.

Now which one makes for the more efficient radiator[1]?

Answer: I have no idea.[2]

What's the best way to find out for what bands (if any) my current
antenna is best suited? Would something like the Antenna Analyzer II
(http://www.amqrp.org/kits/antanal/) or the 'Tenna Dipper
(http://4sqrp.com/kits/kits.htm) answer this question?

Those two devices only seem to be good at answering the following
question: "At what frequency does this antenna/feedline have the
lowest SWR?". I don't think that this question is the same question
that I asked -- in other words, I am not convinced that the
antenna/feedline with the lowest SWR is necessarily the most efficient
radiator, especially when an antenna tuner is involved.

To those who say "the one that gets you more QSOs is the best", I'd
like to say that since the weekend I set up the antenna (the weekend
of the last California QSO Party) I've had *one* QSO, and now that
person (several towns away) can't clearly hear me when I transmit with
100W on any of the four HF bands I've tried.

Does anyone have any real answers (or at least good suggestions to
collect more information) for me?

Jack.
(a little frustrated, yeah)

[1] I define the most efficient radiator as the one which pushes out
the most signal for a given power level on a given frequency. If
this definition is in error, helping me correct this could render
the entire point moot.

[2] Well, I'm almost positive the order is: dipole, lightbulb,
toaster element, dummy load. Almost. I'm not sure where the
dipole fits in, to be honest.
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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On Thu, 11 Mar 2004 20:23:13 -0800, Jack Twilley
wrote:
What's the best way to find out for what bands (if any) my current
antenna is best suited? Would something like the Antenna Analyzer II
(http://www.amqrp.org/kits/antanal/) or the 'Tenna Dipper
(http://4sqrp.com/kits/kits.htm) answer this question?

These are toys when it comes to the grist of your question. No
analyzer will answer what is best as that is a subjective issue.
Further, an antenna has more characteristics than feed point Z which
impact the nature of your enquiry far more.

A low antenna that warms the ground will look like a charmer to the
analyzer, but then so would your dummy load. Get the idea? You
already anticipate this I am sure.

The old methods, prior to the invention of analyzers, encompassed a
simple sanity/reality check with the field strength meter. Put one
100 wavelengths out and take a reading. Do the same with a buddy in
town. The differences should be telling. This will reveal how much
power has escaped the grip of loss.

Repeat with a DX contact (you and your buddy working the same remote
station). You already have a basis of comparison for line of sight
power levels, you can now determine how well your elevation angles
work out. If you buddy comes in #1 and has a higher antenna, you got
a clue where your next step should be. But higher, lower, whatever,
differences will be revealing. No differences? Well then perhaps
doing some Dale Carnegie courses are in order.

73's
Richard Clark, KB7QHC

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"Richard" == Richard Clark writes:

Jack What's the best way to find out for what bands (if any) my
Jack current antenna is best suited? Would something like the
Jack Antenna Analyzer II (http://www.amqrp.org/kits/antanal/) or the
Jack 'Tenna Dipper (http://4sqrp.com/kits/kits.htm) answer this
Jack question?

Richard These are toys when it comes to the grist of your question.
Richard No analyzer will answer what is best as that is a subjective
Richard issue. Further, an antenna has more characteristics than
Richard feed point Z which impact the nature of your enquiry far
Richard more.

That's pretty much what I figured. I tried to provide a definition
for best that was more objective than subjective.

Richard A low antenna that warms the ground will look like a charmer
Richard to the analyzer, but then so would your dummy load. Get the
Richard idea? You already anticipate this I am sure.

Exactly. This is the same antenna that I've mentioned in the past,
less than twenty feet off the ground and less than five feet from the
house (which towers over the antenna by ten feet at its highest
point).

Richard The old methods, prior to the invention of analyzers,
Richard encompassed a simple sanity/reality check with the field
Richard strength meter. Put one 100 wavelengths out and take a
Richard reading. Do the same with a buddy in town. The differences
Richard should be telling. This will reveal how much power has
Richard escaped the grip of loss.

While I don't have a field strength meter, I do have a friend with a
DC-to-daylight receiver. He was able to receive me loud and clear
over a mile away. One hundred wavelengths would be twenty-four miles
- -- if he had a real antenna, he'd be perfectly situated for that kind
of test, but all he has is the whip that came with the receiver, so
I'm not sure that's going to be a valid test.

Richard Repeat with a DX contact (you and your buddy working the same
Richard remote station).

[... rest elided ...]

Ahahahaha. Richard, I've worked a DX contact *once*. That was day
one of the antenna's life, during the California QSO Party, when I
logged a contact with a guy in Germany. I have trouble working people
several towns over, and in fact have had only one QSO since the
weekend the antenna was installed. This part of the test is a little
optimistic.

Richard 73's Richard Clark, KB7QHC

Thanks!

Jack.
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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On Fri, 12 Mar 2004 00:30:57 -0800, Jack Twilley
wrote:
While I don't have a field strength meter, I do have a friend with a
DC-to-daylight receiver. He was able to receive me loud and clear
over a mile away. One hundred wavelengths would be twenty-four miles
- -- if he had a real antenna, he'd be perfectly situated for that kind
of test, but all he has is the whip that came with the receiver, so
I'm not sure that's going to be a valid test.

Hi Jack,

You need a rig with a good, calibrated readout. I should use the word
"calibrated" with care. Actually it needs resolution and stability so
that it can make comparisons. Using a step attenuator and its reading
to achieve the same indication is the best method.

You still need someone else to compare against. Coming in loud and
clear might easily (or poorly) be accomplished driving a leaky dummy
load. A friend of mine once QSO'd her girl friend in AK all while on
her dummy load (20M).

73's
Richard Clark, KB7QHC

Jack,
As stated, the only answer anyone can make to your
questions is, [2] I don't know.
SWR meters and antenna analyzers are nice, and handy,
things to have around, but they require a little thought
in their use. They aren't the "be all, end all" of
antenna instruments by themselves. Probably the most
'handy' measuring device for dealing with antennas is the
yardstick (or meter stick for those that would rather).
Antenna analyzers are probably the most 'handy' gadget
for finding out band/frequency an antenna is made for
that I've seen in years. But, and there are several 'buts'
that have to be taken into consideration when using one.
If you connect an analyzer to the feed line of your antenna
you are measuring where the whole 'system' (feed line and
antenna) are 'resonant', not just the antenna. The feed line
'modifies' what the analyzer 'sees' of the antenna, changing
the answer to, "What is the resonant frequency, and the input
impedance?". To make the antenna 'right', you have to get
rid of the feed line. OR, make it 'disappear' electrically.
You can do that by making the feed line an electrical 1/2
wave length at whatever frequency your antenna is supposed
to work at (or multiples of an electrical 1/2 wave length
if one isn't long enough to reach from the antenna to where
you are doing the measuring). The analyzer readings then
are for the antenna only since an electrical 1/2 wave length
of feed line is 'invisible' to the analyzer. (Takes a different
feed line length for each band.)
**[A thought about 'efficiency' here. Don't worry too much
about
efficiency, it isn't that important really. Of course you want
the most efficient antenna you can have, but that can change
with
any number of things, even with the exact same antenna. (Watch
the
fur being rubbed in the wrong direction with that statement!
LOL)
I'm talking about efficient 'results', not the characteristic
efficiency of a particular antenna. An antenna should be
mounted as
high as possible, away from anything around it. But, you can
only
put one in the space you have available, not always what would
be
the 'best' height/clearance, (right?), so make the best of what
you have and live with it.]**
Use that yardstick to measure the length of your multiband
antenna's elements. That will give you a rough idea where they
'should' be resonant (barring any loading coils, that makes
it a little more difficult). Plugging those lengths into the
'magic' formula, F = 234 / length(feet), will give you a 'ball
park'
idea of frequency for 1/4 wave lengths (one half of each
antenna).
Then it's just a matter of 'tweaking' the lengths for each band.
That doesn't do anything about input impedance, just resonance.
To
match the input impedance is a separate thing, and there are
several
methods of doing that. When both length and impedance matching
are
done, you will have the most 'efficiency' for the antenna in
~that~
particular configuration. It may not be exactly what you want,
but
that's more a result of how/where the antenna is mounted.
Anything and everything can change the usefulness of an
antenna,
which is due to the radiation pattern, which is/can be affected
by
how/where/when the antenna is put up (at night, in a snow storm,
at
the North Pole is the best 'when').
Having used 10 words where 2 may have been more 'efficient',
I'll
shut up...
'Doc

PS - A mobile antenna is usually only around 3 - 20% efficient
compared
to a 'properly' set up fixed antenna. They still work okay.

'Doc wrote:
PS - A mobile antenna is usually only around 3 - 20% efficient
compared to a 'properly' set up fixed antenna.

Dang Doc, a mobile 104" whip is more efficient than that
on the CB band. :-)
--
73, Cecil, W5DXP

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"Richard" == Richard Clark writes:

[...]

Richard Hi Jack,

Richard You need a rig with a good, calibrated readout. I should use
Richard the word "calibrated" with care. Actually it needs
Richard resolution and stability so that it can make comparisons.
Richard Using a step attenuator and its reading to achieve the same
Richard indication is the best method.

None of those things are finding themselves in my junk box at the
moment. In fact, I strongly suspect my HF rig needs to be calibrated
and tuned, and I'm slowly gathering the tools required to do that.
Until then, I've got to work with what I have.

Richard You still need someone else to compare against. Coming in
Richard loud and clear might easily (or poorly) be accomplished
Richard driving a leaky dummy load. A friend of mine once QSO'd her
Richard girl friend in AK all while on her dummy load (20M).

Alas, the sunspots are no longer with us, it seems.

Richard 73's Richard Clark, KB7QHC

Jack.
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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"Doc" == w5lz writes:

Doc Jack, As stated, the only answer anyone can make to your
Doc questions is, [2] I don't know. SWR meters and antenna analyzers
Doc are nice, and handy, things to have around, but they require a
Doc little thought in their use. They aren't the "be all, end all"
Doc of antenna instruments by themselves. Probably the most 'handy'
Doc measuring device for dealing with antennas is the yardstick (or
Doc meter stick for those that would rather). Antenna analyzers are
Doc probably the most 'handy' gadget for finding out band/frequency
Doc an antenna is made for that I've seen in years. But, and there
Doc are several 'buts' that have to be taken into consideration when
Doc using one.

I knew it wouldn't be as easy as "plug it in and turn it on", but the
details are a little hard to find and a little harder for me to
understand. Thanks for explaining.

Doc If you connect an analyzer to the feed line of your antenna you
Doc are measuring where the whole 'system' (feed line and antenna)
Doc are 'resonant', not just the antenna. The feed line 'modifies'
Doc what the analyzer 'sees' of the antenna, changing the answer to,
Doc "What is the resonant frequency, and the input impedance?".

I knew this much, which is why I mentioned "antenna/feedline" in my
original post.

Doc To make the antenna 'right', you have to get rid of the feed
Doc line. OR, make it 'disappear' electrically. You can do that by
Doc making the feed line an electrical 1/2 wave length at whatever
Doc frequency your antenna is supposed to work at (or multiples of an
Doc electrical 1/2 wave length if one isn't long enough to reach from
Doc the antenna to where you are doing the measuring). The analyzer
Doc readings then are for the antenna only since an electrical 1/2
Doc wave length of feed line is 'invisible' to the analyzer. (Takes
Doc a different feed line length for each band.)

This isn't as bad as I thought on first read. The bands I want to
reach with this antenna are 80, 40, 20, 15, and 10. Four of those
five bands collapse into a single case, and the fifth one will
collapse as well due to the odd harmonic thing with 40 and 15, right?
This means a single feedline of 40m should work for all five bands.
My station isn't 40m from my antenna feedpoint, though, so I'll have
to make coils of feedline -- some at the feedpoint, and some at the
station -- will that cause problems?

[... Doc's thoughts on efficiency ...]

Yes, I've got to work with what (little) I've got, true enough.

Doc Use that yardstick to measure the length of your multiband
Doc antenna's elements. That will give you a rough idea where they
Doc 'should' be resonant (barring any loading coils, that makes it a
Doc little more difficult). Plugging those lengths into the 'magic'
Doc formula, F = 234 / length(feet), will give you a 'ball park' idea
Doc of frequency for 1/4 wave lengths (one half of each antenna).
Doc Then it's just a matter of 'tweaking' the lengths for each band.
Doc That doesn't do anything about input impedance, just resonance.
Doc To match the input impedance is a separate thing, and there are
Doc several methods of doing that. When both length and impedance
Doc matching are done, you will have the most 'efficiency' for the
Doc antenna in ~that~ particular configuration. It may not be
Doc exactly what you want, but that's more a result of how/where the
Doc antenna is mounted. Anything and everything can change the
Doc usefulness of an antenna, which is due to the radiation pattern,
Doc which is/can be affected by how/where/when the antenna is put up
Doc (at night, in a snow storm, at the North Pole is the best
Doc 'when'). Having used 10 words where 2 may have been more
Doc 'efficient', I'll shut up... 'Doc

I can see a long weekend in my future. Plug in a noise bridge, check
the resonance, lower the antenna, change its length, raise the
antenna, repeat. Since it's a multiband fan dipole, I'll have to tune
each leg for its own band, right?

Doc PS - A mobile antenna is usually only around 3 - 20% efficient
Doc compared to a 'properly' set up fixed antenna. They still work
Doc okay.

Doc, some days I want to take down all the copper in the yard, buy
myself a mobile antenna, and stick it on a big piece of sheet steel.

Jack.
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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Cecil,
Only if it's got one of them 'Wizz-Band, super-dupper,
all weather, triple-by-pass, monster coils' in it! Ain't
that right?
But then again, any 'full sized' 1/4 wave antenna is
more efficient than the 'usual' loaded mobile antenna for
bands lower than about 15 meters. That's also 'right', is
it not?
'Doc

Jack,
Yep, lots of fun with the up/down/up/down thing, but that's
just the normal part of tuning almost any antenna I can think
of, off hand. For a multiband antenna, multiply all that up
and down stuff for each band (probably). And since each 'part'
of the antenna will affect the other 'parts', repeating the
whole mess is something to count on till all of them are
'right'.
One way of changing the input impedance of a dipole is to
change the 'angle of the dangle' of each 'element'. Making the
angle between the legs of a dipole smaller reduces the input
impedance. So playing with the 'dangle angle' of each part of
the multiband antenna can be one of the simpler ways of doing
the impedance matching. Something to remember is that the
input impedance for all bands will probably never be 'perfect'.
Settling for the 'best' you can get is probably what the
majority
of people do, and just don't worry about it too much. While
looking for the 'best' you can get is the idea, working for
'perfection' is usually a wasted effort.
The thing about using an electrical 1/2 wave feed line is
mostly
for tuning purposes. Once the antenna is tuned correctly the
length
of feed line (coax type) isn't very important, since it isn't
being
used to do any of the impedance matching (right?).
I don't remember what else you mentioned in your post. It's
late,
I just got off work...
'Doc