Antenna analysis
 

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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

'Doc wrote:

Hope you didn't miss my smiley face. I just couldn't resist
pointing out that a RS CB whip is more efficient than the
numbers you quoted. :-)

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?

you said:
A mobile antenna is usually only around 3 - 20% efficient

I don't see any mention of a coil. :-)

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?

you said:
A mobile antenna is usually only around 3 - 20% efficient

I don't see any mention of size or frequency. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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'Doc wrote:
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'.

OTOH, I raised my all-HF-band dipole only once and achieved
a decent match on all HF bands without an antenna tuner.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil,
But did you see my 'tongue in cheek'? Looked
sort of like a ball player three months behind
with his 'Red Man'...
'Doc

Cecil,
Miracles do happen!
'Doc

'Doc wrote:
But did you see my 'tongue in cheek'?

Nope, I didn't, Doc. "Seeing" is not one of my strong
points lately given cataracts and macular degen.
--
73, Cecil http://www.qsl.net/w5dxp



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Jack,

Have you determined that the radio is actually putting out 100W? The light
bulb test should give some indication. When I first got licensed on HF I
went through a bunch of antennas at less than 20 feet with essentially 0
results. For starters, unless you are DX, nobody will talk to you on 75 or
20 m SSB unless you are 5-9. I made my first contact half way across the
country on 15 m by using a 3 el 6 meter beam at 12 feet (In the attic of a 1
story house). Try getting out during a contest, but you really want to get
the wire at least 30 feet up. I don't think you mentioned what the antenna
is, or what bands you have tried.

Tam/WB2TT
"Jack Twilley" wrote in message
...
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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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"Tam" == t-tammaru Tam writes:

Tam Jack, Have you determined that the radio is actually putting out
Tam 100W? The light bulb test should give some indication.

I have an MFJ Versa Tuner II which has a power meter. It's not
laboratory certified, but the needle does go all the way up to 100
when I tune up and transmit.

Tam When I first got licensed on HF I went through a bunch of
Tam antennas at less than 20 feet with essentially 0 results. For
Tam starters, unless you are DX, nobody will talk to you on 75 or 20m
Tam SSB unless you are 5-9.

This disappoints me, and I really hope it's not true.

Tam I made my first contact half way across the country on 15 m by
Tam using a 3 el 6 meter beam at 12 feet (In the attic of a 1 story
Tam house). Try getting out during a contest, but you really want to
Tam get the wire at least 30 feet up. I don't think you mentioned
Tam what the antenna is, or what bands you have tried.

I can't get the wire any higher than it is right now at this current
location. This is pretty much the best I can do, and this little
antenna already totally fills my yard and the yards of each of my
neighbors (with their permission). It's a multiband fan dipole with
three pairs of legs, cut for 40, 20, and 10.

My current goal is to acquire a noise bridge and see where the antenna
resonates, then trim the antenna as necessary until it resonates in
the right places. After that, I'll look into feedline length
modifications as necessary. Hopefully those two approaches will
resolve my current issue.

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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Jack,

Just some comments. I think you have the right kind of antenna with the fan
dipoles. You say it is lower than the house; can't you prop up at least some
of it to the height of the house, or a couple of feet more. Have you
determined that the radio puts out the same power on SSB (whistle) as when
you tune up (on CW?) ?

I made most of my early contacts during contests, by answereing calls from
people who did not have big pileups. If they hear you, they will come back
to you. I did get my SSB DXCC with a Junior beam at 28 feet.

To trim a multiple dipole like yours, you have to trim the lowest frequency
first, and work your way up. I have a 40/17/12 antenna like that, and this
is the only way I got it to convege in EZNEC.

Tam/WB2TT
"Jack Twilley" wrote in message
...
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"Tam" == t-tammaru Tam writes:

Tam Jack, Have you determined that the radio is actually putting out
Tam 100W? The light bulb test should give some indication.

I have an MFJ Versa Tuner II which has a power meter. It's not
laboratory certified, but the needle does go all the way up to 100
when I tune up and transmit.

Tam When I first got licensed on HF I went through a bunch of
Tam antennas at less than 20 feet with essentially 0 results. For
Tam starters, unless you are DX, nobody will talk to you on 75 or 20m
Tam SSB unless you are 5-9.

This disappoints me, and I really hope it's not true.

Tam I made my first contact half way across the country on 15 m by
Tam using a 3 el 6 meter beam at 12 feet (In the attic of a 1 story
Tam house). Try getting out during a contest, but you really want to
Tam get the wire at least 30 feet up. I don't think you mentioned
Tam what the antenna is, or what bands you have tried.

I can't get the wire any higher than it is right now at this current
location. This is pretty much the best I can do, and this little
antenna already totally fills my yard and the yards of each of my
neighbors (with their permission). It's a multiband fan dipole with
three pairs of legs, cut for 40, 20, and 10.

My current goal is to acquire a noise bridge and see where the antenna
resonates, then trim the antenna as necessary until it resonates in
the right places. After that, I'll look into feedline length
modifications as necessary. Hopefully those two approaches will
resolve my current issue.

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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"Tam" == t-tammaru Tam writes:

Tam Jack, Just some comments. I think you have the right kind of
Tam antenna with the fan dipoles. You say it is lower than the house;
Tam can't you prop up at least some of it to the height of the house,
Tam or a couple of feet more.

Nope, I meant what I said when I said I can't get the wire any higher
than it is right now at this current location.

Tam Have you determined that the radio puts out the same power on SSB
Tam (whistle) as when you tune up (on CW?) ?

No, but I'm not really concerned about SSB versus CW -- I'll operate
CW if that's what it takes, and it'll be incentive to finally learn.

Tam I made most of my early contacts during contests, by answereing
Tam calls from people who did not have big pileups. If they hear you,
Tam they will come back to you. I did get my SSB DXCC with a Junior
Tam beam at 28 feet.

My situation is that I can't make a scheduled contact with someone
twenty miles from my house while we're on the phone. "Can you hear me
on this frequency? Let me key up and you tell me if you can hear me."
That's the kind of thing I'm talking about. Worrying about how to get
lots of contacts is way way in the future -- I'm fixed on worrying
about whether my equipment is even working.

Tam To trim a multiple dipole like yours, you have to trim the lowest
Tam frequency first, and work your way up. I have a 40/17/12 antenna
Tam like that, and this is the only way I got it to convege in EZNEC.

That's the plan, once I get the noise bridge. My environment is too
complex for me to attempt to model it with EZNEC.

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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"Jack Twilley" wrote in message
...
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Tam Have you determined that the radio puts out the same power on SSB
Tam (whistle) as when you tune up (on CW?) ?

No, but I'm not really concerned about SSB versus CW -- I'll operate
CW if that's what it takes, and it'll be incentive to finally learn.

That's what I am concerened about. You may have a bad mic, or just not
modulating due to some failure. When I wasn't able to get out, I could
alwayds talk to locals. Try CW/carrier with your friend. He doesn't have to
know CW if you are on the phone and he knows your frequency. I would do it
on 10m, away from anybody else. You know you can get 20 miles on CB with 5W,
and you have 100.

Tam/WB2TT

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"Tam" == t-tammaru Tam writes:

Tam Have you determined that the radio puts out the same power on SSB
Tam (whistle) as when you tune up (on CW?) ?

Jack No, but I'm not really concerned about SSB versus CW -- I'll
Jack operate CW if that's what it takes, and it'll be incentive to
Jack finally learn.

Tam That's what I am concerened about. You may have a bad mic, or
Tam just not modulating due to some failure. When I wasn't able to
Tam get out, I could alwayds talk to locals. Try CW/carrier with your
Tam friend.

I've tried just keying up and I could be heard a mile away, but not
twenty.

Tam He doesn't have to know CW if you are on the phone and he
Tam knows your frequency. I would do it on 10m, away from anybody
Tam else. You know you can get 20 miles on CB with 5W, and you have
Tam 100.

Excellent point.

Tam Tam/WB2TT

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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Keep us posted as to what you find out. We could try a sched if it works at
all. I have a lot of free long distance on my cell phone for coordination. I
am in NJ.

Tam/WB2TT

There is no zero or dollar sign in comcast.

Jack Twilley wrote in message ...
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"Tam" == t-tammaru Tam writes:

Tam Jack, Have you determined that the radio is actually putting out
Tam 100W? The light bulb test should give some indication.

I have an MFJ Versa Tuner II which has a power meter. It's not
laboratory certified, but the needle does go all the way up to 100
when I tune up and transmit.

Well, you know the radio works...



I can't get the wire any higher than it is right now at this current
location. This is pretty much the best I can do, and this little
antenna already totally fills my yard and the yards of each of my
neighbors (with their permission). It's a multiband fan dipole with
three pairs of legs, cut for 40, 20, and 10.

Your antenna is *very* efficient on those three bands, unless you have
coax or connection problems and power is not making it to the antenna.
BTW, the 40 legs will work 15 ok, if you tweak the match with the
tuner...Will be pretty efficient on 15 also as a 1.5 wl dipole.

My current goal is to acquire a noise bridge and see where the antenna
resonates, then trim the antenna as necessary until it resonates in
the right places.

Good idea. You shouldn't really need the tuner.

After that, I'll look into feedline length
modifications as necessary.

Should be unneeded. If coax length radically varies SWR, you need a
1:1 balun or choke to cut radation from the shield.

Hopefully those two approaches will
resolve my current issue.

Actually, I don't think you have a problem, assuming no coax or
connector problems. Does the receive noise level, and signal levels
sound fairly normal, or dead? I think the main problem is trying to
work locally using ground wave, with an antenna that is poorly suited
for that. But, you should usually be able to work 40m in the day,
being it's mainly NVIS. 20 miles is a long way for a low horizontal
dipole to work locally without the help of skywave. A purely
horizontal antenna has no groundwave, if no vertical feedline
radiation, etc. It has a space wave, but it's going to be hard to work
20 miles over the noise. If both of you had verticals, it would
probably be easy. As far as comparing antennas, all you have to do is
use a antenna switch, and see which is best on receive. Operation is
reciprical 98.8 % of the time, so a transmit test is unneeded. You
should be having no problems working 40m in the day, or even 20m to
stateside stuff. 10m local will be very tough, but you should be able
to work some skywave. A vertical is much better for 10m local. 20 ft
high is high enough to work for medium distance skywave. Maybe not a
barnburner, but it should be working for general gov work...I've run
many lower than that when camping, and had no problems. If you can't
hardly work *anyone*, I would check your connections, and coax , etc.
Also, if you use the tuner for now, use the bare minimum inductance to
get a usable match. That will help reduce tuner losses, which can
climb to 20% or so if too much coil is used.
I would eventually tune the antenna up, and dump the tuner. There is
no real need for it, unless you go off far from where you normally
have it tuned. IE: work some CW when the antenna is tuned for the fone
band. MK

Jack Twilley wrote in message

BTW, if you have the legs in the same direction, and close together,
coupling can be a problem. As one mentioned, always start with the
lowest band first, and go up band by band. If you have a coupling
problem, it will almost always be one of the higher band legs being
effected by a lower band leg. You can usually get a usable match if
you vary the wire length. Try to get each band under 2:1 SWR. I run
multi leg dipoles here, but I run mine in different directions and
have few coupling problems. IE: if I had a 40 dipole braodside E/W,
I'd run the 20 dipole N/S. Sometimes if you do have a coupling
problem, just moving the higher band leg a few feet can cure the
problem. You will almost never see a higher band leg effect a lower
band to any great degree. MK

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"Mark" == Mark Keith writes:

[...]

Jack I have an MFJ Versa Tuner II which has a power meter. It's not
Jack laboratory certified, but the needle does go all the way up to
Jack 100 when I tune up and transmit.

Mark Well, you know the radio works...

At least enough to move that needle, or to come in on my friend's
DC-to-daylight receiver as I previously mentioned.

Jack I can't get the wire any higher than it is right now at this
Jack current location. This is pretty much the best I can do, and
Jack this little antenna already totally fills my yard and the yards
Jack of each of my neighbors (with their permission). It's a
Jack multiband fan dipole with three pairs of legs, cut for 40, 20,
Jack and 10.

Mark Your antenna is *very* efficient on those three bands, unless
Mark you have coax or connection problems and power is not making it
Mark to the antenna. BTW, the 40 legs will work 15 ok, if you tweak
Mark the match with the tuner...Will be pretty efficient on 15 also
Mark as a 1.5 wl dipole.

Providing the wires haven't stretched too much over the past six
months, or something else that might be wrong. Oh, and yes, all of
the dipole legs are coplanar, and I can't change that, so I'll have to
be careful when I tune them.

Jack My current goal is to acquire a noise bridge and see where the
Jack antenna resonates, then trim the antenna as necessary until it
Jack resonates in the right places.

Mark Good idea. You shouldn't really need the tuner.

I acquired an MFJ noise bridge with the help of Dave Platt, and here
are the results from some rough measurements at the rig (not at the
antenna!):

Frequency Depth R X Expander Resistance Reactance Impedance
3.750 4 D +25 No 122 28.67 125.32
7.150 2 A/B -25 No 14 -20.17 24.55
14.175 0.5 A/B +175 No 14 30.85 33.88
21.225 4.5 E +150 Yes 903.88 663.97 1121.54
28.850 0.5 A/B -100 No 14 -38.54 41.00

"Depth" is a rough estimate of how deep the null was when the
measurement was taken -- my rig has a 0-10 scale and the measurements
began when the noise was around 7 or 8, usually. The next three
columns were my readings, and the final three columns are the reported
values, in ohms.

The first thing to note is that the readings which resulted from the
deepest nulls are the readings which provide the most reasonable
impedances. This tells me that I'm getting sensible readings,
although I do need more practice with the device -- it's terribly
twitchy.

I plan on trying to find the resonant frequency of the antenna over
the next couple of days, with the goal of shortening (or lengthening)
the individual wires this weekend.

Jack After that, I'll look into feedline length modifications as
Jack necessary.

Mark Should be unneeded. If coax length radically varies SWR, you
Mark need a 1:1 balun or choke to cut radation from the shield.

I have two chokes in my feedline currently -- one about a foot from
the antenna feedpoint consisting of eight or nine turns of coax about
an air core (a Folger's coffee can was used for wrapping), and one
about a foot from the rig consisting of three large type 43 ferrite
toroids with three loops of coax passing through all three toroids.

Jack Hopefully those two approaches will resolve my current issue.

Mark Actually, I don't think you have a problem, assuming no coax or
Mark connector problems.

When conditions change for the worse with no obvious reason, I start
to consider the possibility that a problem exists. I can't blame
sunspots for everything, so I'm looking into how my antenna may have
changed since it was installed.

I just completed another test of my antenna. I set the antenna tuner
to "bypass" so I could use its SWR meter without affecting the
tuning. Then, for each of the five bands I want to use, I tuned up on
the dummy load, then switched over to the real antenna and checked the
SWR. Here's the results:

Frequency Dummy Antenna
3.750 1:1 infinity
7.150 1:1 2.5:1
14.175 1.05:1 3:1
21.225 1.1:1 3:1
28.850 1:1 1.9:1

There may be a correlation between these SWR measurements and the
impedance values shown above -- the three bands which had lower
impedance values also have lower SWR values, but none of them look
particularly healthy.

Mark Does the receive noise level, and signal levels sound fairly
Mark normal, or dead?

My experience aside from working from this location is limited to
Field Day, which isn't really helpful. On some bands I get tons of
receive noise, on others I get less.

Mark I think the main problem is trying to work locally using ground
Mark wave, with an antenna that is poorly suited for that. But, you
Mark should usually be able to work 40m in the day, being it's mainly
Mark NVIS.

NVIS is still a mystery to me, and I need to learn more about it.

Mark 20 miles is a long way for a low horizontal dipole to work
Mark locally without the help of skywave. A purely horizontal antenna
Mark has no groundwave, if no vertical feedline radiation, etc. It
Mark has a space wave, but it's going to be hard to work 20 miles
Mark over the noise. If both of you had verticals, it would probably
Mark be easy. As far as comparing antennas, all you have to do is use
Mark a antenna switch, and see which is best on receive. Operation is
Mark reciprical 98.8 % of the time, so a transmit test is unneeded.

I don't have any antenna against which to compare this one, though.

Mark You should be having no problems working 40m in the day, or even
Mark 20m to stateside stuff. 10m local will be very tough, but you
Mark should be able to work some skywave.

I'm currently unemployed, so I've got time for this kind of testing.
Tomorrow, I'll try 40, 20, and 10 in the morning (eight to ten), in
the afternoon (two to three), at sunset (five to seven), and at night
(nine to ten). I'll post the results tomorrow night.

Mark A vertical is much better for 10m local. 20 ft high is high
Mark enough to work for medium distance skywave. Maybe not a
Mark barnburner, but it should be working for general gov work...I've
Mark run many lower than that when camping, and had no problems. If
Mark you can't hardly work *anyone*, I would check your connections,
Mark and coax , etc.

I've already talked about having checked connections. I really think
the next step is to change the lengths, but I want to make sure I
understand the noise bridge's results first.

Mark Also, if you use the tuner for now, use the bare minimum
Mark inductance to get a usable match. That will help reduce tuner
Mark losses, which can climb to 20% or so if too much coil is used.

I've always done that, but mostly because that's what the antenna
tuner documentation says to do, not because I knew why. :-)

Mark I would eventually tune the antenna up, and dump the
Mark tuner. There is no real need for it, unless you go off far from
Mark where you normally have it tuned. IE: work some CW when the
Mark antenna is tuned for the fone band. MK

That's exactly why I bought the tuner -- that, and so I'd have an SWR
meter in the shack.

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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"Jack Twilley" wrote in message
...
I tuned up on
the dummy load, then switched over to the real antenna and checked the
SWR. Here's the results:

Frequency Dummy Antenna
3.750 1:1 infinity
7.150 1:1 2.5:1
14.175 1.05:1 3:1
21.225 1.1:1 3:1
28.850 1:1 1.9:1
Jack,
I don'r have any experience with the noise bridge, but based on the SWR
readings, I would do the following:

Since you have no 80m radiator, ignore that band for now. Measure the SWR at
7.0 and 7.3+ to determine whether the 40m wire is too long or too short, and
trim to size. Repeat at 14.0 and 14.3+, and 28.0 and 28.5(?), assuming you
want the most used part of 10m. I guess you are useing the 40m radiator on
15.

Tam/WB2TT

On Tue, 16 Mar 2004 22:58:46 -0800, Jack Twilley
wrote:

I just completed another test of my antenna. I set the antenna tuner
to "bypass" so I could use its SWR meter without affecting the
tuning. Then, for each of the five bands I want to use, I tuned up on
the dummy load, then switched over to the real antenna and checked the
SWR. Here's the results:

Frequency Dummy Antenna
3.750 1:1 infinity
7.150 1:1 2.5:1
14.175 1.05:1 3:1
21.225 1.1:1 3:1
28.850 1:1 1.9:1


Hi Jack,

If you can, move the Dummy Load to the end of the transmission line
and repeat the measurements.

73's
Richard Clark, KB7QHC

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Richard, moving the dummy load to the end of the transmission line is
an excellent idea, and I really wish I could do it easily, but the
paint can I used doesn't have a handle. I'll try to work something
like that out this weekend.

Jack.
(looks like I'll have *lots* of data)
- --
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 Wed, 17 Mar 2004 15:47:44 -0800, Jack Twilley
wrote:

Richard, moving the dummy load to the end of the transmission line is
an excellent idea, and I really wish I could do it easily, but the
paint can I used doesn't have a handle. I'll try to work something
like that out this weekend.

Jack.

Hi Jack,

This is where you could as easily use a 50 Ohm resistor and your noise
generator. There would be less interfering signals to confuse the
data.

You could also throw a deliberate mismatch onto the end like a 200 Ohm
resistor. What value is that? If you measured 1:1, it would indicate
you have an extremely lossy line (which tends to smooth out mismatches
and gives some antenna inventors that warm snuggly feeling that they
have licked the experts).

73's
Richard Clark, KB7QHC