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VK8AA - Northern Territory 2006 (CQWW SSB
Contest)
By
David Burger, VK2CZ
Operating as VK8AA,
Zone 29
This years operation was planned with doing something I had
never before attempted
or experienced, both in antennas and operating challenges.
Having explored some
interesting remote island operations for the past 3 years (google
VK9XD), the
infrastructure and support needed on this operation was not
(economically) available
at VK9X, VK9C and VK9L.
Having a lot of support hardware still in storage with Mark
Sellers VK8MS, Darwin
became a focus due to the small incremental amount of effort
needed to carry off
something large. Practically the only challenge was to tackle a
larger antenna.
Establishing the venue at the Darwin Surf Lifesaving Club was
pretty straightforward,
and securing the construction crane from Sitzler Brother
constructions proved more
challenging. Darwin is in the grip of a major construction boom,
and it came down to
my prior experience as a client that tipped the scales to get
this handy temporary
tower for a weekend.
Next was to work out what the something interesting and
challenging was. Always
wanting to use a 40m beam of any description, a few commuting
trips to work with
the laptop established a full size 40m beam was OK. Projecting
my 65' long yagis I
had used in Sydney (on the 10m band), I worked out that a 5
element yagi was the
target performance I wanted.
The design came down to the design shown in Figure 1. The design
shown in Red was
implemented. While the design shown in black is marginally
better, it turned out that
there was not enough open real estate to assemble it. Finding
over 600 square metres
of open space is more difficult in cities than you think.
Darwin is arguably the only airport in Australia not subject to
a curfew, so logically
arriving or departing Darwin is mostly midnight through to 3am.
Arriving at 00:30
local on Thursday 23rd, it wasn't until 2am before getting into
bed with bags and
rental car in hand. Sleep deprivation day 1.
Getting the material to site and access to the Lifesaving Club
venue happened around
3pm, and managed to get the boom assembled by dark. Ninety five
percent of
materials were sourced locally in Darwin in the previous months,
with a major
delivery of small aluminium tubing from Adelaide.
Friday 24th, the measure and assembly of the 5 elements sounded
easy. With around
100m of elements to be made in the blistering tropical sun and 9
litres of sports drink
consumed, the balun, hairpin and feed cable happened literally
with the crane
rumbling onto site. In 20 minutes, the antenna was in the air at
around 80' ... BUT,
the droop on the all elements meant it was not possible to lower
the antenna to
perform a mechanical balance adjustment OR a feedpoint match
adjustment.
The mechanical design of the yagi concerned me more from getting
things physically
balanced and not introducing yet more stress into an already
heavily stressed
structure. A lateral approach to getting an 'automatic' balance
with 5 degrees of
horizontal worked out perfectly once it was in the air. Note -
it was simply not
possible to lift the yagi beforehand to even do a test balance.
For those of you who have worked in the tropical heat, you will
understand that the
mind plays serious tricks... the result was having to re-work a
couple of elements due
to jamming, mis-measurement, errors and other silly mistakes. I
will discuss these
only over a beer.
Having read of others having real hassles with yagi matching on
40m, I applied what
I'd learned of this simple match on the 10m and 15m bands. The
result was a flat
VSWR response from 7150 thru to 7300khz. Down at 7020 however,
the VSWR
was about 2.5:1 - so mental note to keep that as my lower SSB
limit. [ I know many
CW pundits will scream at this point, but here in VK, SSB at
7020 is still legal, and as
CW is no longer officially recognised here, so too the CW
segments will become
softer ].
Saturday 28th. Arrive on site around 7am after a breakfast of
watermelon, mango,
banana and coffee. Manage to setup a low dipole for the 40m band
about 100m away
from the big yagi with an A/B switch. I know I had promised YT6A
and CN7J
some time on 75m, but that antenna succumbed to the tropical
brain fade I had
yesterday.
Setting up the gear, I had borrowed a tired TL922 amp from Mark
VK8MS to keep
transport issues simple. One tube was effectively black and a
quick power test showed
it was struggling to make 300watts output ? just a fraction too
much to be classed as
low power. At this stage of exhaustion from Friday, I was
entirely grateful to have
any amplifier. Sleep deprivation day 2.
Contest kicks off at 09:30 local.. signals from EU require
pre-amp to hear and then
gone by 10:30am. Flick to 15m for a few QSOs on the low dipole
and manage 2
QSOs on 40m by 3pm. By 4.00pm local, I have 12 countries and 8
zones in the log
from Central & North America - and the sun is still way up in
the sky !
Manage around 270 QSO's the first night, I still did not have a
feel for how the yagi
played. It was evident however, that I was working anything that
I cared to point the
yagi at. The gravity of this observation had not yet sunk in
until I wanted zone 38
and 39... which I got within 5 minutes of 'walking' the yagi
toward Africa.
There is a fond term used by the RAAF at Jindalee near Alice
springs where they coin
the term ?Walk the Array?.. effectively a 3km running track
around the OTHR array.
Walking this 40m 5 element yagi around with ropes was remarkably
similar, where I
think I walked about 3 km in circles under the big yagi holding
a rope over my head.
The yagi inertia was also much higher than imagined too, no
sharp movements,
gradually nudging, almost like manoeuvring a 90? sail boat in a
harbour ? by hand.
Sunday 29th. Make the realisation that I could compete with the
big guns on 40m
[NQ4I, VE7SV and others], I decided to hold a frequency in a
couple of sessions in
the US band and later the JA/EU band area. After being subject
to the worst verbal
abuse ever heard in a contest by the ZL6QH station, I figured I
had annoyed him
somehow, but as I do not accept being spoken to in such a
fashion, deserved or
otherwise... well lets say they did not get zone 29 on 40m from
me...
Also witnessed the stress of a 'top' USA station 40m operator
from the 3 district who
actually tried to push me off 7080 ish.. and actually responded
to by QRZs on 7080
ish by activation his callsign voice keyer for about 40 seconds
!! That would have
needed deliberate 'CHANGE' or VFO swap action... so it was far
from the
accidental out of band incursion which happens... I know I would
not be afforded
similar courtesy if I tried to keep 2 frequencies clear on 40m
during any contest.
The correlation of big M/M station operators being courteous is
now in ruins on the
noise floor of my receiver. mmm... ZL6QH was also a big M/M
station too... maybe
they do not screen their operators skills..
Moving to positive experiences, I managed close to 600 QSOs in 5
hours after dusk,
defending my run frequency, and working key targets like JT. The
IC756 Pro 3
suffered some weird behaviour too... competing with full scale
signal (60dB) over S9
signals in the broadcast segment and that was with 18dB of front
end attenuation
made the rig need a power on reset a few times! Not sure if this
is normal.
Unfortunately many stations had me logged as VK9AA even with
persistent attempts
at correcting it. VK9AA was not active on 40m at all during the
event. I wish big
stations would take less notice of their super check partial
database... probably more
their loss once they realise.. I wonder how to say 8 in
Italian.. there it is again.. big
stations !!
With about an hour before the big yagi came down, I still did
not have traditionally
easy Countries like France and Croatia. Focusing on EU in pounce
mode, I rounded
them out... missed other easy nearby countries, VK9s, Maldives,
Solomons, Papua
New Guinea, New Caledonia and Vanuatu.
The crane needed to be back on site by 7:00am Monday, so the
yagi was on the beach
at 6:15am, with 3 hours left in the Contest. Weigh up making a
handful of QSOs on
the dipole or use the cool morning twilight to dismantle the yagi before the
scorching sun comes up. Dismantling the yagi by 9:00am without
heat exhaustion was
the best decision. Sleep deprivation day 3.
On dismantle, little things were observed with the yagi being in
the air for 60 hours. Some pop rivets had sheared, two of the elements had shifted
position about 50mm
and all unexplained. The clamps were very tight, pop rivet joins
were all duplicated or
triplicated... left me wondering.
With nowhere to store the big yagi parts, I had to cut up about
25kg of aluminium and
toss it, hairpin, some clamps, 40m wire dipole etc in the metal
re-cycling bin.
Managed to keep some parts to bring back to Sydney, but
saddening none the less.
Flying out of Darwin at 00:30 local on Tuesday morning took me
into Sleep
deprivation day 4, where I slept like a lamb.
Initial tallies look I have touched or possibly surpassed the
Australian record on 40m
SSB. I guess it will come out in due course.
What's next ?? |
