"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

"Ed" wrote:
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...
________________

Just don't expect that the S-meter so "calibrated" is reading the real value
of the incident field arriving at the rx antenna. It won't be, unless that
calibration includes (exactly) the real-world performance of the receiving
antenna system at each frequency, including line loss, local reflections,
and other factors.

Otherwise the reading still will be given in fairly meaningless, relative
terms -- the same as S-units.

RF

Just don't expect that the S-meter so "calibrated" is reading the real
value of the incident field arriving at the rx antenna. It won't be,
unless that calibration includes (exactly) the real-world performance
of the receiving antenna system at each frequency, including line
loss, local reflections, and other factors.

Otherwise the reading still will be given in fairly meaningless,
relative terms -- the same as S-units.


The bottom line for the Rx, all it cares about since it doesn't know
what kind of antenna is feeding it, is the signal strength at the
input.... so I'd say a calibrated microvolt reading reflecting that
strength is not very meaningless at all. Any changes in the antenna
system will of course change that, but the whole point of any antenna
work is to maximize the signal voltage to that rx input, so I'd think a
calibrated reading would be extremely useful over an S meter alone.


Ed K7AAT

Ed wrote:

The bottom line for the Rx, all it cares about since it doesn't know
what kind of antenna is feeding it, is the signal strength at the
input.... so I'd say a calibrated microvolt reading reflecting that
strength is not very meaningless at all. Any changes in the antenna
system will of course change that, but the whole point of any antenna
work is to maximize the signal voltage to that rx input, so I'd think a
calibrated reading would be extremely useful over an S meter alone.

I'm afraid it might require more than simple calibration. The S-meter
typically just shows the AGC voltage. The AGC response is only
approximately logarithmic, and depends on the gain characteristics of
the various stages being controlled. Gain characteristics are commonly
very temperature sensitive, so any calibration scheme would have to take
that into account, as well as the common deviation from true logarithmic
response of the various stages. Calibration would also be different on
different bands, with and without preamplifier or attenuators, etc.

Of course, you could make a receiver with very nearly true logarithmic
response, by use of one of the excellent, wide dynamic range log amps
which are available these days. But however much you or I might like
one, the vast majority of amateurs couldn't care less about what their S
meter is really indicating, so they wouldn't pay the added cost for it.

On top of that, most amateurs would consider a 6dB-per-S-unit meter to
be "dead", and would rather have it wiggle more.

Roy Lewallen, W7EL

"Ed" wrote:
The bottom line for the Rx, all it cares about since it doesn't know
what kind of antenna is feeding it, is the signal strength at the
input.... so I'd say a calibrated microvolt reading reflecting that
strength is not very meaningless at all.
___________

Received signal strength, whether in terms of relative S-units or the
measure of real incident fields, is at least as much the result of local
conditions as of the ERP of the transmission source on the path toward the
receiver, the frequency, and propagation conditions.

So the received signal strength indication, whether relative or "real,"
isn't a hugely significant indicator of any of these parameters.

RF

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 -