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

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