Ah indeed Richard -- some Ham DXers use stereo headphones where the
earpieces are out of phase.

--
Caveat Lector



"Richard Clark" wrote in message
...
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

It may be possible to get even more improvement by slowly adjusting the
frequency setting of the Steppir over a wide range. The would steer its
nulls around and let you find the best s/n.

Bob W8ERD



In article ,
Allodoxaphobia wrote:

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

Excellent point. That might account for my "odd observation". I have
usually seen the effect when noise levels are high -- mostly due to storm
activity -- and the noise is probably directional in these cases.

Bill
W2WO


"Crazy George" wrote in message
...
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

NO RF GAIN CONTROL -- HERESY

--
Caveat Lector



"Bill Ogden" wrote in message
...
I always operate CW this way --- always have since my first S-85 receiver.
I fully agree that it improves CW readability. On SSB, I sometimes turn
the
RF down (on my Omni 6+) until the meter reads zero on the background
noise.
This seems to help a little, but not to the extent it does for CW.

The absence of a full-time RF gain control has caused me to delay ordering
an Orion; I am still thinking about it.

Bill
W2WO

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

There are several possible causes here.
Probably, on the design frequency, its antenna is probably matched to 50
ohms , for good transmission. A matched antenna does not necessarily give
the best S/N for reception, and usually a mismatch does. Its hard to
calculate.
One filing mentions the possible change in pattern, and therefore a possible
change in S/N.
Suggestion- make a number of measurements, and if it hold up, send a note
about it to QEX. Include as much info as you can, especially the SWR or
better the antenna impedance on the different frequencies.
w4mb

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


There are several possible causes here.
Probably, on the design frequency, its antenna is probably matched to 50
ohms , for good transmission. A matched antenna does not necessarily give
the best S/N for reception, and usually a mismatch does. Its hard to
calculate.

Although this can be true at VHF/UHF, where the receiver noise
dominates, it's not true at HF, where the observation was made. At HF,
external noise dominates, so the quality of impedance match makes no
difference in S/N ratio.

One filing mentions the possible change in pattern, and therefore a
possible change in S/N.
. . .

I'm certain that's the explanation (assuming it's not a mistaken
subjective observation) -- the noise is coming pedominantly from one
direction, and by tuning the antenna a pattern null was created in that
direction. Signals from other directions are then stronger than the
reduced noise.

I've often directed my 40 meter 4 square array toward the southwest to
put a null toward the U.S. Midwest and Gulf Coast, where a lot of
thunderstorms occur in the summertime. VKs jump out of the noise when I
do that. Rotatable loop receiving antennas are often used in the same
way, to null out noise coming from one direction.

Roy Lewallen, W7EL

I am not satisfied that the original poster has not made a "mistaken
subjective observation"

Don't think we have heard from him on this aspect.

--
Caveat Lector



"Roy Lewallen" wrote in message
...
bob wrote:
Expressed another way, is a non-resonant antenna sometimes better for
reception than a resonant antenna?


There are several possible causes here.
Probably, on the design frequency, its antenna is probably matched to 50
ohms , for good transmission. A matched antenna does not necessarily give
the best S/N for reception, and usually a mismatch does. Its hard to
calculate.

Although this can be true at VHF/UHF, where the receiver noise dominates,
it's not true at HF, where the observation was made. At HF, external noise
dominates, so the quality of impedance match makes no difference in S/N
ratio.

One filing mentions the possible change in pattern, and therefore a
possible change in S/N.
. . .

I'm certain that's the explanation (assuming it's not a mistaken
subjective observation) -- the noise is coming pedominantly from one
direction, and by tuning the antenna a pattern null was created in that
direction. Signals from other directions are then stronger than the
reduced noise.

I've often directed my 40 meter 4 square array toward the southwest to put
a null toward the U.S. Midwest and Gulf Coast, where a lot of
thunderstorms occur in the summertime. VKs jump out of the noise when I do
that. Rotatable loop receiving antennas are often used in the same way, to
null out noise coming from one direction.

Roy Lewallen, W7EL