"Roy Lewallen" wrote in message
...
I'm glad to see that my chiding has had a positive result.

Be sure you calibrate your S-meter on each band you'll be using it on,
and that the RF gain control and any preamplifier and input attenuator
settings are the same as they are when making measurements.

Especially when comparing horizontal and vertical antennas, you'll
likely have to make several measurements over a period of time. I've
seen many cases where one antenna is a good 20 dB stronger than the
other, then over the next minute or so their relative strengths reverse.
This is due to polarization rotation of the received signal. On 40 and
80 meters at least, this is common and often has a period of around a
minute or more. Really makes me chuckle when I hear "Ok, this is antenna
1. Now this is antenna 2. Which is stronger?"

If neither antenna is consistently stronger than the other, you can put
a fixed attenuator is line with one of the antennas and the step
attenuator in line with the other to make comparison easier.

People who blindly assume the marks on their S-meters are 6 dB apart
should take a good look at your calibration results.

Roy Lewallen, W7EL

Mike Coslo wrote:
Based on another thread a few weeks back in which Horizontal dipoles
were being compared to Vertical antennas, and from a little chiding from
Roy, W7EL, I decided to do some testing on my own personal versions of
the two.


My setup is:

Icom IC-761
Antenna 1 - Homebrew OCF dipole at ~ 50 feet.
Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground.


Part one of this experiment is to calibrate the S-meter. I found that
trying to calibrate the thing with on-air signals was a nuisance, and
probably wouldn't be as accurate, so I used a signal generator.

I started out with a +20 signal, then worked my way down.

+20 start
S9 -18 db
S8 -23 db
S7 -26 db
S6 -29 db
S5 -32 db
S4 -35 db
S3 -37 db
S2 -39 db
S1 -41 db

All in all, I would have to say that the meter tracks very well from S8
to S4, and the only place that wasn't that great was from S9 to S8. But
considering the transient nature of the signals we are receiving, I
would have to day that the S-meter is of reasonably close accuracy.

With my newly calibrated S-meter I am ready to start looking at what the
two different antennas are doing for me. I have a coaxial switch to jump
back and forth between the two. My initial impressions are that there
are some surprises. The difference in noise levels varies by antenna by
band. On some bands the vertical is noisier, and on others it is the OCF
dipole. Especially intriguing is that on PSK mode, where I can see
several signals at one time, switching between antennas will attenuate
some signals, while other signals increase in strength. I think that my
vertical works better than I gave it credit for, but If I definitely
want *both* antennas.

Next installment will be the band to band comparison of the two antennas
with some numbers.

Installment three will be an investigation of that PSK signal strength
business.

- 73 de Mike KB3EIA -


Man, this is Ham Radio at its best!

west
AF4GC

Roy says,
People who blindly assume the marks on their S-meters are 6 dB
apart
should take a good look at your calibration results.

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

The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do
with which antenna produces the stronger received signal. It is purely
a comparison. Just use the same meter throughout the tests.

Roy, you must be still be using that ancient receiver. No doubt it is
working fine. But you still refer, quite arbitraliry, to your personal
S-meter as the North American Calibration Standard. Must everybody
else fall into line? Not me!
----
Reg.

Reg Edwards wrote:
Roy says,
People who blindly assume the marks on their S-meters are 6 dB
apart
should take a good look at your calibration results.

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

The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do
with which antenna produces the stronger received signal. It is purely
a comparison. Just use the same meter throughout the tests.

Roy, you must be still be using that ancient receiver. No doubt it is
working fine. But you still refer, quite arbitraliry, to your personal
S-meter as the North American Calibration Standard. Must everybody
else fall into line? Not me!
----
Reg.

I hate to call a liar a liar, but sometimes it's hard to take. You're
lying again, Reg.

I've never referred to my rig's meter as a calibration standard. I've
used it as an example many times of a meter whose response is far from
the 6 dB per S unit many people assume. It's my argument that any S-Unit
"standard" at all is of no use, except by misleading people into
thinking that it has some relation to the markings on their S meters.
Mike's measurements serve the same purpose.

And you've claimed your rig has an adjustment allowing calibration of
its S-meter to 6 dB per unit, but have never been willing to share the
type of rig or what the adjustment control designation is. Frankly, I
believe you're fabricating that, also.

It's sad -- you have a lot to offer, but somehow feel compelled to come
up with pure fabrications from time to time. It makes some of us view
everything else you say with some skepticism.

Roy Lewallen, W7EL

And you've claimed your rig has an adjustment allowing calibration of
its S-meter to 6 dB per unit, but have never been willing to share the
type of rig or what the adjustment control designation is. Frankly, I
believe you're fabricating that, also.


This thread raises a possible marketing opportunity for someone. Yes,
it is quite unlikely, due to their non-linear construction, that an
analog meter would properly display S units in 6dB increments.

So..... someone ought to design a nice little digital unit that could
somewhat easily be hooked up to most radio Rx circuits, and be capable of
displaying S units or microvolts (selected at push of a button) and also
have a fully adjustable means to calibrate the S unit readings so that
they would, in fact, display in linear 6dB increments, and actual
microvolts at Rx input, too. Probably wouldn't sell cheap, but there
would be those hams who'd love to have such a device.

I suppose just a display for microvolts would suffice, though, and
that isn't hard to do at all. or just calibrate and re-paint the S meter
face to match...



Ed K7AAT

Roy, you appear to have mislaid your sense of humor. Hope you recover
it soon. ;o)
----
Reg.

Reg Edwards wrote:
Roy says,
People who blindly assume the marks on their S-meters are 6 dB
apart
should take a good look at your calibration results.

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

The calibration of S-meters, 3dB or 6dB per S-point, has nothing to do
with which antenna produces the stronger received signal. It is purely
a comparison. Just use the same meter throughout the tests.

It does allow me to make a stab at comparing those two antennas. As I
continue on this test, it would be nice to have something that has some
sort of calibration. Otherwise we might as well just go to say "works
great" or "doesn't work well for all measurements.

- 73 de Mike KB3EIA -

The hour is growing late and the urge to tell a story is upon me. Note,
that unlike others, I never imbibe alcoholic beverages. This is a true
story.

A large, expensive, rotatable LPDA was erected on a tall tower and
tested in an informal way with a receiver and short-wave broadcast
transmitters as signal sources. Nulls were where they were supposed to be.
F/B was roughly what was expected. Front lobe seemed about right.

A month went by and it was time to perform more careful measurements. A
180 swing while listening to a distant carrier suggested that there was more
gain off of the back than off of the front! Wise men pondered that this
must be a measurement error.

Impedances were very close to expected. The scheme that was used to
determine that the antenna needed to be brought back to earth were these:

(Keep in mind that this is a LPDA and not a Yagi.) A 6db pad was put in
the line to ensure that the nonexistent impedance changes with no change in
frequency would not affect things. An accurate, step attenuator was then
added in the line. (Should sound familiar.) Antenna was pointed towards a
known very high power broadcast station with a known location such that the
expected receiving take-off angle was about 6 degrees. Bandwidth was made
very narrow and centered on the carrier. Enough attenuation was added to
get the S-meter to average either side of a mark. The attenuation was
varied by one db up and down with several minutes at each level. Then the
antenna was rotated 180 degrees and the change in attenuation to return to
the same indication was noted. Ouch. Repeated several times it became
clear that the antenna had reversed direction and (are you listening?) a
number for the difference in gain (at the angle involved) and the
uncertainty in that number was crafted. Lord K. should have said - and may
have said - that all measurements comprise at least two numbers: an
estimate expressed as a number and an estimate of the uncertainty in the
first number expressed as a number.

The evidence was conclusive that something had happened. A search for
causality took place with the assistance of NEC. With a good deal of
speculation and noting how the largest elements were constructed, it was
speculated that one of the rearmost elements (or a part of one of the
rearmost elements) may have become detached electrically. An NEC simulation
was produced that fit the data. No, this is not proof, but it did furnish
additional support for the need to lower the antenna. More support came
from measurements at the high end of the frequency range where no anomalies
were noted and where the long elements would not be expected to play much of
a role.

At significant cost and effort, the antenna was lowered and it was found
that one of the mechanical connections of a sleeve with normal screw had not
been tightened in a rear element. The conclusive proof was that the screw
had not "cut." Apparently, a month of very sight corrosion had isolated
part of an element.

So, be my students and find the lessons in this tale. Make a list.

73 and I am off to bed, perchance to dream of antennas, Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"

J. Mc Laughlin wrote:
The hour is growing late and the urge to tell a story is upon me. Note,
that unlike others, I never imbibe alcoholic beverages. This is a true
story.

Despite his enjoying wine, I believe Reg's stories to be true also! 8^)

A large, expensive, rotatable LPDA was erected on a tall tower and
tested in an informal way with a receiver and short-wave broadcast
transmitters as signal sources. Nulls were where they were supposed to be.
F/B was roughly what was expected. Front lobe seemed about right.

A month went by and it was time to perform more careful measurements. A
180 swing while listening to a distant carrier suggested that there was more
gain off of the back than off of the front! Wise men pondered that this
must be a measurement error.

Impedances were very close to expected. The scheme that was used to
determine that the antenna needed to be brought back to earth were these:

(Keep in mind that this is a LPDA and not a Yagi.) A 6db pad was put in
the line to ensure that the nonexistent impedance changes with no change in
frequency would not affect things. An accurate, step attenuator was then
added in the line. (Should sound familiar.) Antenna was pointed towards a
known very high power broadcast station with a known location such that the
expected receiving take-off angle was about 6 degrees. Bandwidth was made
very narrow and centered on the carrier. Enough attenuation was added to
get the S-meter to average either side of a mark. The attenuation was
varied by one db up and down with several minutes at each level. Then the
antenna was rotated 180 degrees and the change in attenuation to return to
the same indication was noted. Ouch. Repeated several times it became
clear that the antenna had reversed direction and (are you listening?) a
number for the difference in gain (at the angle involved) and the
uncertainty in that number was crafted. Lord K. should have said - and may
have said - that all measurements comprise at least two numbers: an
estimate expressed as a number and an estimate of the uncertainty in the
first number expressed as a number.

The evidence was conclusive that something had happened. A search for
causality took place with the assistance of NEC. With a good deal of
speculation and noting how the largest elements were constructed, it was
speculated that one of the rearmost elements (or a part of one of the
rearmost elements) may have become detached electrically. An NEC simulation
was produced that fit the data. No, this is not proof, but it did furnish
additional support for the need to lower the antenna. More support came
from measurements at the high end of the frequency range where no anomalies
were noted and where the long elements would not be expected to play much of
a role.

At significant cost and effort, the antenna was lowered and it was found
that one of the mechanical connections of a sleeve with normal screw had not
been tightened in a rear element. The conclusive proof was that the screw
had not "cut." Apparently, a month of very sight corrosion had isolated
part of an element.

So, be my students and find the lessons in this tale. Make a list.


Lesson #1 - Put the thing together correctly. Check the connections.
Check it again.


Lesson #2 -some people needed to hone their troubleshooting skills. If
the antenna had performed well during the initial tests, using an
analysis program is probably the last thing to do. The time to do
analysis was long past.

I don't know much about antennas, (which is why I'm here) but I do know
troubleshooting. All the numbers that popped up on the tests and the
simulations were just blind alleys for y'all to go down and get beat up
in. Something changed in that month. Is it likely that the laws of
physics changed? Much more likely something in the installation was at
fault. The antenna should have been lowered when the second tests were
so different than the first ones. Of course following rule #1 would have
obviated the need for that!




73 and I am off to bed, perchance to dream of antennas, Mac N8TT

8^) -73 de Mike KB3EIA -

ORIGINAL MESSAGE:

Mike Coslo wrote:

So, be my students and find the lessons in this tale. Make a list.



*********** REPLY SEPARATOR ***********

My very first thought was you were receiving an LP signal instead of
SP.

Shows how a DXer thinks. :-)

73, Bill W6WRT