Sunday, December 16, 2012

ARRL 10 metre contest

I had decided a few months ago already that I wanted to make a serious entry with a view to putting in a good QRP score on SSB, operating portable-style from my usual seaside location.
I’d done a lot of prep work with the 10m antennas, trying out 2 element and 4 element designs, with a 2 element phased design in the works. I had the option to use the FT-1000 MkV Field in order to do SO2V, the poor man’s version of SO2R, CQing on one VFO and doing s+p on the other. So I was quite prepared.
At the beginning of the week prior to the contest, conditions were very poor, but the NOAA forecast was that it would get better, with an SFI forecast of 130 and low absorption. However it just didn’t happen and on Saturday morning, SFI was at a meager 95. Great for low bands, not so hot for high bands....
I trundled on down to the port and set up. In the end I used my Kenwood TS850, since I hadn’t had time to set up the audio on the Field and also it didn’t fit in the car. I set up the quarter wave on the car and the 2 element vertical yagi and had a tune around. Heard JY4NE and called. And called. And called. He finally pulled me out of the noise. No such luck with VK6IR. Or with RT4RO. After an hour, and only one more QSO in the log, I realized that there was no way I was going to get any kind of record on QRP, so I cranked up the wick to 100w. This time I managed to get VK6IR and a couple of others in the log but really not a lot happening.
I decided that since there was nothing happening, it might be a nice idea to try out the new phased design. This is based on the notes in the WX0B stackmatch. Basically it consists of two identical half wave verticals, in my case centre fed. If they are spaced a half wavelength apart, when fed together using a 0.41 wavelength phasing line from the phasebox to each vertical, it will give a broadside pattern with 4dB gain over a single vertical. It can also be fed to give endfire in both directions, with up to 6dB gain with a half wave of spacing. With the centre fed antennas, I used a third fishing rod in the centre to support the box. This meant that I was able to get full spacing (5m between verticals and 2m80 lines means the box cannot be on the ground!) and also keep feedlines quite horizontal to avoid feedline radiation. Unfortunately the clamp was too big and I needed to tape it all up provisionally. This is what it looked like:
How did it work? Well to be honest I noticed very little difference on RX. And there was hardly anyone to test it with on TX. I decided to take it down again and put up the 2 element parasitic I’d started with, on the basis that it was almost less work getting out of the car and moving the reflector every once in a while. This may be a design to think about for a more permanent installation, or for a band where antennas are so big they need to be guyed, or radials need to be moved, etc. But for vertical dipoles on 10 and maybe 15, I think the parasitic design is a better all round solution.
The day wore on and we continued to have what Bob K8IA calls “spotlight propagation”. I would hear one loud Finn, for example, for about 5 minutes, but only one. Then a state might come up out of the noise for a few minutes. Some were even less, the exchange having to be quick and not be left with one of us shouting,….”number?...number?....numberrrrrr?????????????!?!?!” At the end of Saturday, I’d worked all continents, 33 multipliers, but only 53 QSOs!
And that was how it ended. I got up on Sunday and saw the SFI had crept up to 100, but I decided to spend the time doing other things instead. I kept an ear on the radio at home and heard the states coming in at dusk, but in spite of that I think I took the right decision. Next year will be better, right??
Points to note:
 - I might try to recreate the 2 ele phased array using end fed antennas, easier setup which would allow the phase box to sit on the ground.
- End fed antennas also take out the guesswork on whether your feedline is horizontal enough and if its affecting the performance.

- In the afternoon a strong gust of wind blew the reflector down and the SWR went up. I checked, and on the rig it showed resonance at 29.4. I double checked on the analyzer and it showed the same. Something local affecting the SWR? Or did I screw up when I was labeling the elements after putting away the 4 element last time? 
- I plugged in my 12V to 19V DC to DC converter for the netbook and zas! S5 to S9 of QRN. Trying to remember what I used to power the PC last time. And thinking, last time was on 40m, maybe it was making that noise then and I hadn’t noticed? On marginal 10m, you can tune across the band even with S2 noise and think there is no one there. Need to check whether the netbook will charge on 12V straight connection to the battery.

Next contest….um, not sure. ARRL DX for sure, but maybe something in between?

1 comment:

EA2CCG Joaquín Montoya said...

A good choice good be UBA Contest next January.

I was looking for this contest and when I scanned the band I give it up.

Today conditions were better :(