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It's January
here in Queensland, Australia and that means it's hot - about 30-31
degrees Celsius according to the Weather Bureau... in practice more
like 35 degrees ... and the sun burns exposed skin quickly. I went
back to QG61OU / Beechmont in the Gold Coast (famous for its sun
& surf) hinterland for this year's Summer Field Day and even
though I wore a hat most of the time, the top of my head still got
sunburnt. The only time I didn't wear a hat was when I was turning
the antennas or starting the generator - and that was only for a
few minutes at a time. I guess that mentioning the weather seems
a strange way to start a report on the radio happenings on a Field
Day but when we have this type of event in summer, the heat is a
major factor. I was lucky though - no rain during the course of
the day or afternoon storm to chase me into packing up early.
This outing
was a little different from the 2009 field days ( details of each
from the menu at top of page) because this time I took a camper
trailer as the shelter from the elements - as the photos below show.
The radio gear had changed a little but not much. The radio gear
for 6 & 2 metres SSB and FM was still the Icom IC-7400, the
driver for the 70cm transverter was still the Icom IC-718 but the
transverter was new (more on that later). The homebrew 23cm transverter
and Kenwood TR751A transceiver were the same as last time and no
changes were made to the antennas at all. The power source was still
the 2 x 12v car batteries in parallel as used last time ( Spring
09 FD ) plus the same petrol generator. After all, the gear
worked out pretty well last time so why make massive changes.
Reading the
above makes it seem like nothing had changed from last year but
that isn't really true. A simple fact is that active VHF
& UHF FD stations seemed to be in the minority in South East
Queensland. I seemed to end up working the same dedicated stations
on each available band after the 3 hour repeat period and apart
from some brief bursts of sporadic E on 6 metres to VK2 & 3.
The best contacts were on 2 metres SSB - north to Glenn VK4BG at
Hervey Bay (318km) and to south to VK2MAX (330km). The high tension
powerline noise was a problem but it was different in nature - this
time it was near-constant while during previous visits it has been
"bursting" then quiet for a while as the wind gusted and
then eased.
One thing
very noticeable about the propagation on 6m this time around was
how quickly the signal "landing zone" was shifting. One
minute a signal (eg VK2 or 3) was S9 on the meter and the next it
was in the noise so people who didn't do a quick RST-serial and
grid exchange didn't get a complete QSO. Stations to the north of
me were often then heard exchanging/reporting the same station typically
at 59 after it had quickly faded here. There will be a number of
6m stations who may quote a contact with me in their logs but they
don't appear in mine simply because they took too long with "general
details" and the signals faded before the necessary
contact detail exchanges could be completed (and thus have the contact
validated). In those cases I was forced to simply delete the partial
details from the log using the "Clear" button in VKCL.
I wasn't
the only one with problems on 23cm but my LO was pulling with modulation
(read that as at high current drain) on SSB - so a number of the
later contacts on this band were conducted on FM on 1296.160, .170
or .200. Fortunately most of the 23cm operators could easily switch
to FM so it made the process even quicker than trying to resolve
the multitude of SSB signals that were supposed to be
on 1296.150 or .160.....
There was
a little breeze coming through the windows of the camper trailer
from time to time - but it was still HOT ! The windows were all
open, the door to the west was left open and the northern entrance
was simply left open too. The extra heat coming off the radios wouldn't
have even been noticed even given the high transmit duty cycle of
the IC-7400 on 2m & 6m SSB. Maybe I will try to find one of
those old rotating-style 12v car fans (provided it is a brushless
type) and add it to the field kit for future events.
The generator
was run for about 1/2hr at a time when the battery bank voltage
dipped below 12.0v so about every 1 to 1-1/2 hours towards the end
of the event, particularly trying to coincide the running with "slow
times" (i.e. between station re-works). The DC generator output
is rated at 8 amps for those who are interested in that aspect.
The power drain was all of the transceivers with varying transmit
cycles, the transverters (ditto) and the PWM charger for the Compaq
notebook computer - and it had accessories all demanding power.
All in all, the battery bank held up well.
As mentioned
above, the 70cm transverter was new. Very new in fact and only finished
2 days before the event. A few weeks before, it was an idea in my
mind then a circuit board layout on the PC and a number of plastic
bags containing mainly surface mount components with a major hope
that I would get the project ready in time for this field day. I
produced PCBs using positive resist material, mounted components
and finally powered it up one section at a time. Yes, I encountered
difficulties because I was not just copying an existing design but
melding from a few "idea sources" including a DEM 432/28
design, some from the Minikits 23cm design, plus some local work-ups
and making a complete unit from those ideas. In the creation process,
it appeared that at some stage I over-drove the Mitsubishi RA60H4047M1
RF power block and damaged that beyond repair (1st section blown,
output still ok). Mark from Minikits urgently despatched me a 30
watt RA30H4047M and I was able to install it and have the transverter
producing 30+ watts at 432 in time for the FD outing. I made mistakes
in its design but I think that it was good experience (if not costly..
RA60H..'s are not cheap.) and will give me a better background to
approach new projects using SMD components and techniques. More
details on my experiences in creating this transverter will appear
on another web page on this site shortly - after I have time to
document the final version.
The following
thumbnail images will enlarge if you roll your mouse cursor over
them....
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