I would suggest that anyone that strapped for cash use transmission line
segments for impedance matching. That is about as cheap as it gets.

"Art Unwin KB9MZ" wrote in message
m...
Seems like a lot of hams with limited resources are still compelled
to operate on many bands with just a long wire and a tuner.
The wire is inexpensive but the tuners are not. Thus my present
project.
I was given a Palomar enginnering balun with 5 female connenection
which by selection can match a antenna in steps from 5 ohms to over
450 ohms
in a series of steps. I am presently rigging it up so that all
steps can be switched thru remotely by a single motor. The switching
arrangement
is the main challenge since inexpensive means simple.
Now I have not measured losses of the balun before hand because the
switching
challenge is what is driving me.
Anybody have any thoughts about what I should expect from this
balun other than knowing that it is not a tuner as is generally known
since
it does not have the ability to obtain the priceless 1:1 condition
that so many desire?
Regards
Art

On Thu, 31 Jul 2003 17:07:10 -0700, wrote:

Given that a 1dB change is NOT SUSPOSED to be noticed (without a meter, in
hearing, sight, ect. ), anyhow, Just what would be the Noticeable effect of
/ = .1 dB in the real world ? Would , say, 2/10's really kill you, or
1/100th dB extra get you that last DXCC country? As I say, am very cynical
when ANYTHING gets into these kinds of numbers! Jim NN7K

KB7QHC wrote:
-------------------------------------------------
50:12.5 Ohm with an insertion loss of around 0.1dB or less over the
interval of 100KHz to 30MHz.
AND THAT IS NOT THE BEST EXAMPLE OF LOW LOSS!
73's Richard Clark, KB7QHC

Hi Jim,

Cynical? This 0.1dB corresponds to about 2% error from perfect where
too many think that 5% error is the worst they have to suffer from
making a power measurement with their Bird (which actually doesn't do
nearly that well in the first place due to these accumulations of
error). It doesn't take long for error to accumulate to the 10's of
percent where you couldn't convince the bench tech that he has too
many places of precision in his pronouncement of measuring 104.5W
(when it was in fact closer to somewhere between 85W to 115W).

I can well anticipate the "so what?" rebuttal. "Who needs 5%
accuracy?" being another. The general rule of thumb demands that your
standard exhibit 3 times the accuracy of the instrument being
calibrated (the Bird is already dead on arrival using this 0.1dB loss,
if it were not characterized already). With an out of whack Bird, you
barely qualify any power measurement to within 15% (and there are more
sources of error than the BalUn used to isolate the Bird). Again, I
am being generous with the 3 times rule (professionals generally seek
5 times and are more comfortable with 10 times). But this is all
really the provence of the professional Metrologist, not the Amateur.
For the Bench Tech that confidently made the 104.5W measurement (not
knowing it was in fact closer to 60W) would hardly know it through
contacts where they barely noticed the less than 1 S-Unit difference.

Returning to this 0.1dB, it also represents a heat burden of 20W (or
more, I am being generous) for each 1KW passing through. This is a
lot of heat for small packages carelessly regarded as being trivial
(after-all, who can see 0.1dB on their S-Meter?). There have been
more than single reports of Hams writing here in astonishment of their
BalUns exploding. Blame the BalUn seems to be a popular ballad played
to that audience. Others pronounce with hushed tones of reverence
remonstrating mankind for drifting from the true path of the air wound
BalUn (or choke, what will you) mindless of the same loss, but
gratified through ignorance of the greater heat mass.

This 0.1dB in the wrong hands is clearly an example of extravagant
dismissal or myopic attention. And speaking of hands, how long would
you consider it trivial if you had to hold onto the sucker for 20
seconds?

73's
Richard Clark, KB7QHC

Jimmy wrote:
I would suggest that anyone that strapped for cash use transmission line
segments for impedance matching. That is about as cheap as it gets.

Yep, I bought an SGC-500 amp and didn't want to spring for a high power
tuner. So I vary my window-line length to obtain a match.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
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"Jimmy on reading the postings over time I see a lot of
people asking about the G5RV which is an inexpensive way of
of operating on many bands. I thought that maybe a inexpensive way
of matching such an antenna would be a cheap sort of tuner.
I don't need a tuner, it was just an idea that popped
into my head. Clark raised the subject of excess heat
that I hadn't thought of but I am enjoying the challenge
of putting together suitable mechanisms that would not be
subject to breakdown, that one could place at a antenna feed point.
If it explodes it would be more spectacular than having a
neon light blinking during radio operation !
If one must have 1: 1 SWR at all times then they can spend a $200
amount or more to buy the SGC tuner ( I thing that in the name
of the automatic tuner which I believe is limited with respect
to power.)
The mechanism I am making is a star shaped wheel with a slot in
each point.
It has a interconnecting rotary switch that sweep each transformer
connection and when it has rotated once engages the star wheel
so that it rotates a distance equal to the transformer connection
where it stays in place for the next rotary switch rotation.
Making the parts from a plastic sheet used to replace a glass
window pane plus the use of a small hand grinding tool.
Duing this in the garage to escape the heat




Jimmy" wrote in message r.com...
I would suggest that anyone that strapped for cash use transmission line
segments for impedance matching. That is about as cheap as it gets.

"Art Unwin KB9MZ" wrote in message
m...
Seems like a lot of hams with limited resources are still compelled
to operate on many bands with just a long wire and a tuner.
The wire is inexpensive but the tuners are not. Thus my present
project.
I was given a Palomar enginnering balun with 5 female connenection
which by selection can match a antenna in steps from 5 ohms to over
450 ohms
in a series of steps. I am presently rigging it up so that all
steps can be switched thru remotely by a single motor. The switching
arrangement
is the main challenge since inexpensive means simple.
Now I have not measured losses of the balun before hand because the
switching
challenge is what is driving me.
Anybody have any thoughts about what I should expect from this
balun other than knowing that it is not a tuner as is generally known
since
it does not have the ability to obtain the priceless 1:1 condition
that so many desire?
Regards
Art

W5DXP wrote in message ...
Jimmy wrote:
I would suggest that anyone that strapped for cash use transmission line
segments for impedance matching. That is about as cheap as it gets.

Yep, I bought an SGC-500 amp and didn't want to spring for a high power
tuner. So I vary my window-line length to obtain a match.

Cecil, the idea that you have is quite unique but I was thinking
of the newby ham. To capture the future hams of tomorrow we must
enable them to get them on the air as quickly and cheaply as
possible and not dissuade them in any way as to how much they
will be paying in the future, and that is where my thoughts lie.
If a newcomer is to put up a G5RV so that he can get on the
air quickly,I thought that buying a RF transformer would be a
quick way of getting on the air and getting the taste for ham radio.
To be honest Cecil no newby is going to struggle with your method
in his early days.
If one could arrange a way to run thru a series of impedance ratio's
with just one knob then we have hooked those who are curious, even
when using the most plainess of wires or the gutter we have fed the
mind, remote control systems can come later. Frankly when you are
hooked by ham radio money ceases to become an issue.
Art

I think it all boils down to signal to noise.
If you are trying to communicate with another station and he is putting out
100 watts and is not being copied and then he puts out 110 watts and you can
copy him that is what counts.

Bill N4WC

wrote:
Given that a 1dB change is NOT SUSPOSED to be noticed (without a meter, in
hearing, sight, ect. ), anyhow, Just what would be the Noticeable effect of

/ = .1 dB in the real world ? Would , say, 2/10's really kill you, or

1/100th dB extra get you that last DXCC country? As I say, am very cynical
when ANYTHING gets into these kinds of numbers! Jim NN7K




KB7QHC wrote:
-------------------------------------------------
50:12.5 Ohm with an insertion loss of around 0.1dB or less over the
interval of 100KHz to 30MHz.
AND THAT IS NOT THE BEST EXAMPLE OF LOW LOSS!
73's Richard Clark, KB7QHC

"Bill" wrote
I think it all boils down to signal to noise.
If you are trying to communicate with another station and he is putting
out
100 watts and is not being copied and then he puts out 110 watts and you
can
copy him that is what counts.

===============================

Bill, sorry to be so pessimistic.

If, because of bad signal to noise ratio you can't copy him when he's using
100 watts, then, as sure as eggs don't bounce off concrete, there's no hope
of any detectable improvement by increasing power to 110 watts or 0.4 dB.

Suppose when he's using 100 watts you can hear only 25% of words (or morse
characters). So you can't copy him.

If he doubles power to 200 watts you will still read only 40% of what he
says. So you still can't copy.

If he doubles power again to 400 watts you will be able to copy 60% of what
he says. You will still be in big trouble.

At 800 watts 80% of words (or characters) will be OK but it's not solid
copy. Requests to repeat will be common.

At 1600 watts 99% of words (or characters) will be OK and that's solid
enough.

There are many assumptions in the foregoing crude analysis. But as many have
experienced it is typical.

Claude E. Shannon's (of Bell Labs) original classical paper on the subject
of "Communication in the Presence of Noise", Jan. 1949 can be downloaded (I
have just discovered) by doing a Google on the title. Radio and phone
engineers had been trying for 40 years to describe in precise mathematical
terms the effects of noise and cross-talk in a communication channels. The
transistor had just been invented. So had PCM pre-war. But progress in the
design of the vast communication digital networks then envisaged and which
we now see was being impeded by the lack of understanding of the effects of
ever-present random noise.

It was basically a problem in Statistics. But Shannon went off at a tangent
back to Geometry where Pythagorus the ancient Greek had begun. He translated
the statistical problem into one of calculating the number of small spheres
which can be packed inside a much larger multi-dimensional sphere. The
calculating procedure acquired the everlasting name of "Ball Packing". It is
not difficult to understand. It was Shannon's dazzling multi-coloured flash
of inspiration which did the trick. His name has gone down in history. Think
of him the next time your electric light dimmer-switch goes faulty.
Following Shannon progress forged ahead. In-words such as signal-to-noise
ratios and error-rates became very popular.

A one-dimension sphere is a dot. A 2-dimension sphere is a flat circular
disk. A 3-dimension sphere is a ball. Followed by N-dimensions, all of which
have a surface area and and a volume involving Pi.
----
Reg.

And we can look at it going the other way. I can
run my FT-817 with its 5 watt signal for a lot
less money than my friend Jim can operate his
kilowatt. If the band is open The difference
between my 5 watt signal and his 1000 watt signal
is 2 or three S units at the far end of the
circuit. Not enough to be really noticeable. If
the band is closed, nobody is talking long
distance, the band is closed. Now when conditions
are marginal he has a decided advantage. Right
now I am happy burning a kilowatt of power
purchased from the electric company every 15 hours
while he gets about 20 minutes operating time for
his station for the same dollars.

--
73 es cul

wb3fup
a Salty Bear

"Ian White, G3SEK" wrote in
message ...
Reg Edwards wrote:
Suppose when he's using 100 watts you can hear
only 25% of words (or
morse characters). So you can't copy him.

If he doubles power to 200 watts you will still
read only 40% of what
he says. So you still can't copy.

If he doubles power again to 400 watts you will
be able to copy 60% of
what he says. You will still be in big trouble.

At 800 watts 80% of words (or characters) will
be OK but it's not solid
copy. Requests to repeat will be common.

At 1600 watts 99% of words (or characters) will
be OK and that's solid
enough.

There are many assumptions in the foregoing
crude analysis. But as many
have experienced it is typical.


Typical for a machine, but not for a human
being. For humans, "copying"
very weak speech or Morse is mostly about
*understanding* it as
language.

In conversational speech, we don't always hear
every word. Our minds are
remarkably good at filling in gaps by using the
broader context of the
whole sentence. Even if you don't hear a word
clearly, you can hear a
word was there and your mind will automatically
make a good guess, based
on what we did hear before and after. It happens
all the time, in
conversations both on and off the air, and you
don't even notice
yourself doing it.

It's more obvious when copying Morse, where we
more often fill in
individual letters, but sometimes also whole
words. We make very clever
guesses about what the letter could have been,
based on what we did
manage to hear.

Often there is a threshold effect. Below that
threshold, you can hear
quite a lot but it doesn't make sense as
language. Just above the
threshold, it clicks into context and you can
understand a whole
stretch... and then maybe we lose it again.

It's also like listening to a language we only
"half" know. That doesn't
mean we understand a certain percentage of
individual words, as a
machine might. The way it really works with
human beings, we're suddenly
delighted to find ourselves understanding whole
sentences... and then,
just as suddenly, we lose it again completely.

The exceptions are for certain key items like a
callsign, name, QTH or
contest exchange. These items come one by one
(without context) and must
be logged with 100% accuracy, so then it's
rather more mechanical like
Reg describes. But even for key words like
phonetics, there is a
threshold between hearing a sound, and that
sound resolving itself into
a recognisable word.

As any DXer knows, the threshold between
"getting it" and "losing it"
can indeed be as little as 1dB. The more serious
you are about working
right down to that threshold, the more that last
1dB matters.


--
73 from Ian G3SEK 'In Practice'
columnist for RadCom (RSGB)
Editor, 'The VHF/UHF
DX Book'
http://www.ifwtech.co.uk/g3sek

"Art Unwin KB9MZ" wrote in message
. ..
W5DXP wrote in message
...
Jimmy wrote:
I would suggest that anyone that strapped for cash use transmission
line
segments for impedance matching. That is about as cheap as it gets.

Yep, I bought an SGC-500 amp and didn't want to spring for a high power
tuner. So I vary my window-line length to obtain a match.

Cecil, the idea that you have is quite unique but I was thinking
of the newby ham. To capture the future hams of tomorrow we must
enable them to get them on the air as quickly and cheaply as
possible and not dissuade them in any way as to how much they
will be paying in the future, and that is where my thoughts lie.
If a newcomer is to put up a G5RV so that he can get on the
air quickly,I thought that buying a RF transformer would be a
quick way of getting on the air and getting the taste for ham radio.
To be honest Cecil no newby is going to struggle with your method
in his early days.
If one could arrange a way to run thru a series of impedance ratio's
with just one knob then we have hooked those who are curious, even
when using the most plainess of wires or the gutter we have fed the
mind, remote control systems can come later. Frankly when you are
hooked by ham radio money ceases to become an issue.
Art

Actually I would think a newbie would be the one most likely to embrace
Cecil's method. Its the guys who have been around a while who want
everything controlled at their armchair(like me). This is not to say that
Cecils method could not be controoled from the shack, Just replace some of
those switches with relays and maybe make some custum impedance feedline for
even a better match that what he shows though you dont really need it. This
sort of setup could even be controlled by a lot of radios that provide for a
means of automatic antenna switching.