I have a new SteppIR antenna to play with and I noticed an odd response. If
I set the beam for 17 or 15 meters but listen on 20 meters I seem to have a
better S/N ratio on signals. If I then switch the beam to 20 meters (while
continuing to listen on 20) the background noise and the signals go up but
the noise goes up more than the signals.

Expressed another way, is a non-resonant antenna sometimes better for
reception than a resonant antenna?

This may be a well-known effect, but it is new to me.

Bill
W2WO

Bill - I have a fairly new 3 element SteppIR and that is not the case with
mine. I wonder if you've done a Calibrate in Setup mode to see if that
makes a difference?

K8AC


"Bill Ogden" wrote in message
...
I have a new SteppIR antenna to play with and I noticed an odd response.
If
I set the beam for 17 or 15 meters but listen on 20 meters I seem to have
a
better S/N ratio on signals. If I then switch the beam to 20 meters
(while
continuing to listen on 20) the background noise and the signals go up but
the noise goes up more than the signals.

Expressed another way, is a non-resonant antenna sometimes better for
reception than a resonant antenna?

This may be a well-known effect, but it is new to me.

Bill
W2WO

On Wed, 26 Jan 2005 10:22:55 -0500, "Bill Ogden"
wrote:
If I then switch the beam to 20 meters (while
continuing to listen on 20) the background noise and the signals go up but
the noise goes up more than the signals.

Hi Bill,

It seems highly unlikely there would be any alteration of S+N/N by a
passive device. More likely is trusting your senses to make this kind
of measurement (which is a poor standard).

Perhaps you can testify this was observed by S Meter readings. Well,
even then, this is another failure in trust unless you have calibrated
your S Meter against a known standard. Problem is that most S Meters
are not linear against their own scale.

This is all a function of the actual ratio being distorted as the
overall levels climb through the meter readings. Let's consider if
you started with S3-S5 (noise-signal+noise, a presumable 6dB
separation) and pushed that up through tuning to achieve S7-S8(a
presumable 3dB separation) then you need to confirm your meter. Is
the S3-S5 separation in fact twice the S7-S8 separation? Feel free to
substitute your own readings (if in fact you based your observations
on this method). The further apart the readings, the more likely you
are to suffer the distortion of meter scaling inaccuracy.

73's
Richard Clark, KB7QHC

On Wed, 26 Jan 2005 10:22:55 -0500, Bill Ogden wrote:
I have a new SteppIR antenna to play with and I noticed an odd response. If
I set the beam for 17 or 15 meters but listen on 20 meters I seem to have a
better S/N ratio on signals. If I then switch the beam to 20 meters (while
continuing to listen on 20) the background noise and the signals go up but
the noise goes up more than the signals.

Expressed another way, is a non-resonant antenna sometimes better for
reception than a resonant antenna?

This may be a well-known effect, but it is new to me.

Not expressly addressing your circumstances: But, I sometimes will
switch to a different antenna on receive to get a better S/N ratio --
even if the sigs drop in level.

E.g., When on 15M, I might switch to the 80/40M dipoles for RCV.
Or, when on 80M, I might switch to the tri-bander for RCV.

( Then, like a klutz, I'll forget to switch back on XMIT. :-)

73
Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK

My observation was based entirely on my ears --- a very subjective
measurement I know. However, the effect was rather striking. It might have
been due to the high noise crashes (when the beam was tuned to the "right"
band) that create more subjective interference due to overloading the ear.

I have heard from others now who mention that using the "wrong" antenna
sometimes appears to improve signal readability. (Of course, this could be
due to polarization differences, etc, etc, that are probably not involved
with the SteppIR setup.)

It is all very subjective and probably not worth a technical debate.
However it would be tempting to utilize the effect if the band changes on
the SteppIR were just a bit faster ---- an if I could remember to retune the
antenna every time before transmitting.

Like most of us, I have noted many times that the ability to clearly copy a
signal (i.e., a comfortable S/N situation) is often not correlated with S
meter readings of the signal or the noise.

Bill
W2WO

Try turning the AGC off, turn the RF Gain way down and the AF Gain up
considerably. Then advance the RF gain until the signal is just copyable in
head phones. Repeat for the two antenna conditions. Make sure your audio
levels are equal.

Military and Ham operators operate this way and claim a SUBJECTIVE increase
in signal to noise over that of a wide open receiver. Technically this
should not be true, Signal to noise ratio should not be reduced by
decreasing receiver gain

But the human ear with its threshold levels, logarithmic hearing, and brain
filtering may account for this.

--
Caveat Lector



"Bill Ogden" wrote in message
...
My observation was based entirely on my ears --- a very subjective
measurement I know. However, the effect was rather striking. It might
have
been due to the high noise crashes (when the beam was tuned to the "right"
band) that create more subjective interference due to overloading the ear.

I have heard from others now who mention that using the "wrong" antenna
sometimes appears to improve signal readability. (Of course, this could
be
due to polarization differences, etc, etc, that are probably not involved
with the SteppIR setup.)

It is all very subjective and probably not worth a technical debate.
However it would be tempting to utilize the effect if the band changes on
the SteppIR were just a bit faster ---- an if I could remember to retune
the
antenna every time before transmitting.

Like most of us, I have noted many times that the ability to clearly copy
a
signal (i.e., a comfortable S/N situation) is often not correlated with S
meter readings of the signal or the noise.

Bill
W2WO

Not odd at all. The noise source is in a side lobe in one case and in a null in the other. Antenna pattern changes all
over the place as you move away from the optimum frequency of a yagi. Happens all the time. I once found a condition
where my HF tribander pulled in a 2 meter signal better than a 10 element 2 meter yagi mounted several feet higher.

--
Crazy George
Remove N O and S P A M imbedded in return address

On Wed, 26 Jan 2005 16:09:34 -0800, "Caveat Lector"
wrote:

Military and Ham operators operate this way and claim a SUBJECTIVE increase
in signal to noise over that of a wide open receiver.

This has been true back when I taught it to my students in the Navy.

Technically this
should not be true, Signal to noise ratio should not be reduced by
decreasing receiver gain

Oh but it should. AGC will compress differences, thus lowering the
subjective ratio in comparison to a non-AGC perception. However, the
fluctuation of all signals will be wider. Myself, I've never been
afraid of automatic circuits, but often I find they are marginal to my
interests and for weak signal detection, I follow the conventions
you've offered.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 26 Jan 2005 16:09:34 -0800, "Caveat Lector"
wrote:
Try turning the AGC off, turn the RF Gain way down and the AF Gain up
considerably. Then advance the RF gain until the signal is just copyable in
head phones. Repeat for the two antenna conditions. Make sure your audio
levels are equal.

Military and Ham operators operate this way and claim a SUBJECTIVE
increase
in signal to noise over that of a wide open receiver.

RC wrote This has been true back when I taught it to my students in the
Navy.

CL writes -- Indeed Richard -- I learned this while in the US Navy in the
50's


CL wrote Technically this
should not be true, Signal to noise ratio should not be reduced by
decreasing receiver gain

CL Writes Here I was comparing S/N ratio with a wide open receiver to a
reduced RF Gain receiver -- both with no AGC. The S/N ratio should be the
same.


RC wrote Oh but it should. AGC will compress differences, thus lowering
the
subjective ratio in comparison to a non-AGC perception. However, the
fluctuation of all signals will be wider. Myself, I've never been
afraid of automatic circuits, but often I find they are marginal to my
interests and for weak signal detection, I follow the conventions
you've offered.

CL writes Ah yes AGC can cloud the issue -- using fast AGC can provide a
greater amplification of the noise (between words) than the signal (if the
signal is strong enough)

But on the other hand AGC can be a big noise reducer if used properly.
Tune in a strong SSB signal on 40M or 80M, with fast or no AGC -- assess the
noise between words. Now use slow AGC and listen to a greatly reduced noise
level (between words)

That is why I advised the original poster to use no AGC when assessing the
two different antenna conditions

But I agree -- use AGC as appropriate.

New operators are inclined to set the RF Gain to max, to read the S-meter.
But the technique of increased AF Gain and reduced RF Gain with no AGC is
used by many experienced ops. Disadvantage is, of course, when a big gun
jumps on the frequency while you are set for no AGC -- ouch my ears. Maybe a
small price to pay in order to pull out that weak one.

Also for weak signal detection, listening with headphones can make a big
difference in comprehension as compared to listening to a speaker. Using the
above techniques and head phones, top notch CW operators can copy code even
when the signal is about the same as the noise.

I can't do this though (;-(
old ears I guess (;-)

--
73 es gd DX -- Caveat Lector

On Thu, 27 Jan 2005 08:11:34 -0800, "Caveat Lector"
wrote:

Also for weak signal detection, listening with headphones can make a big
difference in comprehension as compared to listening to a speaker. Using the
above techniques and head phones, top notch CW operators can copy code even
when the signal is about the same as the noise.

I can't do this though (;-(
old ears I guess (;-)

Hi OM,

Well, back when I was in college physics (before the flood), my
professor put me and a buddy on a task to build the perfect detector.
It correlates perfectly with your advice to use headphones.

He had us build a Synchronous Detector (not a simple device to
construct from tubes and at 455 KHz). Some may be familiar with this
form of detection, and yet they may be ignorant of its best
implementation. For others, this kind of detector is also found in
color TV detection and color information separation. Often the block
diagramming or circuitry is described in terms of I and Q paths. I
won't go into the particulars of design, but I will offer that these
two separate paths when broken out to separate Audio channels, and
then fed to stereo head phones, they offer an unique signal hearing
experience.

Basically, the entire two channel system is completed by the brain
combining phases and providing a perception of the wanted signal being
"heard" in the middle of your skull, while interfering off-frequency
signals are perceive off to one side or the other. In a sense, you
hear an enhanced signal through phase reinforcement.

73's
Richard Clark, KB7QHC