Stew Perry Topband Challenge - Warmup
Call: K1LT
Operator(s): K1LT
Station: K1LT
Class: Single Op HP
QTH: EM89ps Ohio
Operating Time (hrs): 10:20
Summary:
Total: QSOs = 294 Total Score = 1,042
Club: Mad River Radio Club
Comments:
Since the Stew Perry Topband Distance Challenge "Warm-Up" is the first
160 meter contest of the season, I have to catch up with my logging of
my 160 meter station developments.
I've decided to abandon the 8-circle array project for the time being.
The array works, but it doesn't have sufficient output to drive
Softrock style SDR receivers, and one can't do beam steering with a
circular array anyway. You can electronically rotate the pattern, but
steering the beam between the preferred directions causes the pattern
to very rapidly deteriorate. I started to build an electromechanical
steering box (using K7TJR's schematic) but I just didn't get it
finished.
The 8 element broadside/end-fire phased array works very well, so I
decided to repeat that success and build another array broadside to
Japan, to fill in one of the "holes" of the existing array. The
existing array is broadside to North Africa, and as the beam is
steered north, the pattern degenerates to a bidirectional pattern with
directivity about the same as a short Beverage.
The easiest way to build the new array was to put it closer to the
house so I can reuse some of the feedlines from the 8-circle. The new
array is (so far) a 4 element broadside/end-fire array, with
sufficient room to add another pair of verticals to make each
broadside element a three element end-fire array. So the ultimate 6
element configuration has almost as much directivity as the existing 8
element array. In the 4 element configuration, the beam can be
steered to any heading without using relays, which means software can
examine signals from all directions simultaneously. If only the
operator could do the same.
I finished the outdoor part of the construction exercise 2 days before
the contest. However, I found that both of my spare Delta-1010LT
cards had developed some deafness on some channels. It turns out that
some of the very numerous electrolytic capacitors on these cards had
dried up and gone to very low values. Since I don't need very low
baseband frequency response, I was able to use some junk-box tantalum
capacitors to replace the worst of the electrolytic caps. All three
1010LTs are now working adequately, although I should order a complete
set of replacement caps. By the way, I found a schematic of this
board online. If you need it, email me.
I was able to update the software sufficiently to run either receiving
array on the same computer one at a time, but not both simultaneously.
I might need a motherboard upgrade to handle 2 instances of my phasing
program running at the same time. Alternately, maybe some software
optimization is more appropriate. But its more fun to buy new
hardware.
Finally, I discovered that the much lamented northwest noise is
actually two separate noises. One noise actually comes from a set of
poles about 1000 feet southeast of the southern end of the 8 element
phased array. This noise also makes a racket in the 150/300 degree
2-wire Beverage in either direction. Apparently, the noise source is
sufficiently close that it just couples directly with the affected
antennas. All of my 2-wire Beverages are center fed and use the
cheap-and-easy "one end open and the other end grounded" method of
converting the common mode received signal into a differential mode
signal that makes use of the 2 wires as a transmission line to get the
signal to the feed point. Anyway, grounding the open wire at the
Southeast end makes the noise coupling go away, but also makes the
received signal from the northwest go away. I wound a reflection
transformer which seems to reduce the noise coupling, but there is
less received signal than with the open/grounded scheme. More
experimentation is needed here.
The other northwest noise is apparently some very strong but very
short range noise emanating from my neighbor's property. This noise
is just noticeable on all of the Beverages, but mostly on the 300
degree Beverage and second most on the 270 degree Beverage. This
noise gives me great grief trying to receive the Pacific Northwest,
Alaska, and Japan. The noise is apparent on the 8 element phased
array, with greater pick-up on the northern verticals as compared to
the southern elements. On the new phased array, there is a dramatic
difference in output, even between the 2 verticals that are only 60
feet apart. In fact, the output from the most affected vertical is
almost to the point of overloading the ADC.
This noise also sounds a little different than all of the other
power-line noise. It is impulse noise, but the timing of the impulses
is not stable like regular power-line noise. The noise cycles on and
off like a heater might, although the transition is not abrupt. The
noise must be related to some appliance. The noise also has a
spectrum that rolls off very quickly with icreasing frequency. I
can't hear the noise above 80 meters. Perhaps a small DF style loop
and a portable 160 meter receiver will be necessary to go hunting for
this source.
So for actually operating the contest, I didn't use the new phased
array to make any contacts because the neighbor noise was on most of
the time and because I couldn't quickly switch from one array to the
other.
I found that conditions seemed to be "short". The west coast was very
audible and DM grid stations started showing up well before their
sunset. Europe was weak, although occasionally some stations were
moderately strong. I didn't hear anything east of grid KN although I
heard N1LN work a Ukrainian station that I could hear but not copy.
DX worked: DL, E7, F (2), FM, G (4), GM, I, KV4, KH6 (2), PA (3), SM,
VE (many, of course) and XE (2). Much less DX this year than last
year.
After the contest I observed that one OK1 requested that I "listen for
Eu" at a time when I was, in fact, listening for Europe. Also, I was
spotted by a VK, so maybe there was some propagation that I missed. I
didn't hear anything west of KH6. Both of these spots make me think
that I wasn't hearing normally.
I find sitting still in front of the radio at night makes me very
sleepy. So I pushed the office chair out of the way and dragged over
the lounge chair and arranged things so I could just push keys and
flip the audio routing switch while reclining and CQing. This
arrangement kept the sleepiness from being overpowering and allowed me
to stay by the radio longer than otherwise. Of course, when a weak
signal showed up, I'd have to sit up to try different antennas or
adjust the filters. But when such signals appear only once every 10
minutes or so, then the lounge chair might be a decent trade off.
More experimentation needed.
The amplifier needs new tubes. I have a spare set that have been
sitting on the shelf for 8 years but I need to get another set so that
when I return this borrowed amplifier, it has unused tubes.
Equipment: K3, homebrew panadapter (a work in progress), 8 element SDR
receiving system (still need a name for this concept), ETO 91B (thanks
K8ND), 6 2-wire Beverages for coverage every 30 degrees, 65 foot Tee
antenna with 75 125 foot radials under the grass.
Posted using 3830 Score Submittal Forms at: http://www.hornucopia.com/3830score/
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