ARRL 160-Meter Contest
Call: K1LT
Operator(s): K1LT
Station: K1LT
Class: Single Op HP
QTH: Ohio EM89ps
Operating Time (hrs): 28
Summary:
Total: QSOs = 1353 Sections = 77 Countries = 30 Total Score = 310,407
Club: Mad River Radio Club
Comments:
I've done some more work with the Beam Steering Phased Array described
in QEX and reprinted on my web site after being stagnant for the last
couple of years.
Tracking Power Line Noise
As soon as the rain stopped and the weather turned cold, one of the
previously intermittent local noise sources went full-on adding more
than 10 db to the local noise floor. Earlier I bought an MFJ 852
"power line noise tracker" and now I had a chance to use it. I didn't
have to go far. Five poles down the road and around the corner I
found 1 pole under which the 852 would show full scale, even with the
whip antennas partial collapsed. Unfortunately, there was no way that
the power company would be able to fix the noise source before the
contest. I did not try whacking the pole with a sledge, as that
particular location has great visibility and I feared being accused of
being a terrorist.
Beam Steering and Noise Cancellation
Experiments with Eznec showed that one can create a second beam with
an array and add it out of phase with the main beam to add a null to
the pattern in some direction. Note that with only 4 end-fire
elements, the null is not very sharp or deep.
Since the noise source was very close to the phased array I thought
maybe I should just subtract a component from each element from the
overall array and tune the gain and phase of each element by hand. So
Friday afternoon I wrote some code to do that.
By repeated iterations I could reduce the level of the line noise to
where I could hear the normal background noise (other more distant
sources of line noise). I had to repeat this process for each of the
regular beam headings I have configured for the phased array (Europe,
North Europe, New England, Virginia, Caribbean, due West, etc.). I
didn't have time to do every pre-programmed direction, but I thought
if I covered the directions I most often use, I should be safe. I
also had to check that I wasn't canceling all of the received signal
my making sure I wasn't cancel-ling my own transmitted signal. I
figured no more than a 2 db reduction in my own transmitted when
noise-cancel-ling mode is turned on.
Interestingly, the #3 end-fire array did not receive much noise
signal, probably because that particular element is behind a small
hill with respect to the noisy power pole. The other 3 elements can
directly see the noisy pole. When the array is switched to the west,
elements #2 and #3 don't see much noise power, probably because the
noisy pole is directly in line with the #2 element, which can
attenuate the noise because of the element's cardioid pattern, and
because of the hill for the #3 element.
Finally, I found that the cancellation scheme was not very effective
for the directions where the linear phased array degenerates into a
non-optimal end-fire array, presumably because there isn't enough
directivity remaining to form much of a beam.
Noise Canceled Beam Steering Array in Combat
During the contest I found that the array seemed to operate reasonably
normally for the broadside directions, although the optimal beam
heading did not always seem correct for some stations. For example,
New England appears to have split in two, with the two parts migrating
North and South. The noise-cancellation was probably severely messing
with the shape of the beam.
Nevertheless, the noise cancellation made weak signal reception
possible. Turning off the noise cancellation showed that weak signals
would just disappear into the noise and buzzing.
The phased array was not at all useful for receiving signals from the
Caribbean, because the noise was not attenuated in that direction.
I'm sure I missed some Caribbean multipliers.
Although conditions to Europe were very poor, I did work about 11
stations the first night which proved that the noise cancellation
scheme worked. During the day Saturday, I added noise cancellation to
more pre-determined directions and fixed a bug which broke the array
performance in directions for which there was not to be any noise
cancellation. In other words, the first night I couldn't receive weak
signals from Florida or the Caribbean or from Minnesota because I
broke the software.
The second night reception from Minnesota was greatly improved
although I didn't spend much time hunting for Caribbean stations.
Contest Overall
Late the second night, conditions to Europe were more "normal" for
this point in the sunspot cycle. Several Europeans were even copyable
without resorting to ESP-mode. By the end of the contest, I worked 65
5 point stations, compared to 185 in 2010 and 238 in 2009. In fact, I
have to go back to 2006 to find a lower count.
I missed AK, NT, and SDG and didn't hear any VK, ZL, or JA. I was
timing how long to work WAS on 160, and the timer is past 42 hours
now, although I reached 49 states by working KH6 at 0456Z the first
night.
This is my lowest score since 2003, which was the first year I
operated from this location while the house was still being built.
I worked 32 duplicates. Doesn't anyone use logging software in this
contest?
DX worked: 9A (2 and 1 dupe), CE, DL (5), EU (2), F (3), G (8), GD, GM
(2), GW, HB, I (2), LZ, OK (10), OM (2), ON (2), OZ, P4, PA (2), PJ2,
SM, SP, SV, UA (2), UR (4), VP2M, VP5, XE (3), YN, YO, and ZF.
Equipment: K3, beam steering noise canceling phased array antenna /
computer / receiver thingy, ETO 91B (as always, thanks K8ND), 12
Beverages (totally useless because of the noise), 65 foot "Tee" over
80 125 foot radials on the ground, Writelog, and custom software
kludges to tie it all together.
Posted using 3830 Score Submittal Forms at: http://www.hornucopia.com/3830score/
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