Sunday, August 19, 2007

The simpliest tool: a ruler

I made a post in early March In search of the featherweight tribander. I ordered a Mosley Mini-32-A in March with a special request that they make it to break down into 48-inch pieces. Because of this special request, I waited nearly four months for it to arrive and paid another $75 for labor to accomplish the alterations.
I had worried about things like Will it arrive in time for my trip?, How will I erect it on the island?, and Will it perform well enough to justify the weight? The last thing I was worried about was Is it really only 48-inches when disassembled? I didn't check that until this morning. OOPS. It isn't. Oh for goodness sake! I was so worried about checking out the antenna performance with fancy meters and on-air tests that I neglected to use the most simple and important tool: a ruler to see if the darn thing will fit in the case. Sheesh.
The reflector pieces that attach to the boom are both 52.5 inches long with no obvious way to make it shorter. I both angry with myself for waiting so long to verify the antenna dimensions, and a little bemused that nothing is easy with antenna makers! I will call Mosley in the morning and explain the situation. I hope that they will offer to send me a new set of pieces that do fulfill the 48-inch requirement. Otherwise, it doesn't go to St. Kitts. Of course, if they do send new pieces, they will have to be tested and run through the paces as I did with the antenna yesterday in the North American QSO Party. Speaking of which, here's how I did:

Band QSOs Mults
160: 0 0
80: 50 22
40: 149 31
20: 61 26
15: 1 1
10: 0 0
Total: 261 80 Total Score = 20,880

As always, claimed score is just that: my claim. The contest sponsor (The National Contest Journal) will compute my score after deducting all my miscues from the log.
I used this contest to put the new beam through its paces. The antenna assembled quickly and was upon the 20-foot mast and guyed in about 45 minutes. I also have a G5RV hidden in the trees so I could alternate between the two antennas to do A/B comparisons. I was surprised to find that the G5RV at 60+ feet with its arms in a flat-top configuration outperformed the beam most of the time. There are several reasons for this (though I am still working this out in my head). Here's my thinking:
  1. The beam was only at 20 feet - The G5RV was up about a half wavelength on 20m; the beam is obviously very low for that band. I don't know what that did to the takeoff angle of the beam.

  2. The beam was only "generally" pointed - Sure, the beam gives you some gain in the direction it is pointed, but as you move off to the side, the gain drops. I had it pointed WSW (or so I thought), but I wasn't all that careful. There were a couple of times that the beam was stronger than the G5RV during the contest. The two stations I remember talking with where the beam beat the dipole were both in the American Southwest (Arizona and Southern California). So, they were both very far away and in the direction I was generally pointing (maybe I had the antenna pointed too far South?)

  3. Maybe the beam takeoff angle was too low for a domestic contest - Maybe the beam's takeoff angle was too low for close-in contacts. When I'm on St. Kitts the beam width will allow me to point generally to Europe or North America and the low takeoff angle will work better with everybody I'm interested in far away.

  4. Maybe the beam takeoff angle was too high - Maybe it is just nuts to expect the beam to perform well if it is mounted so low. It is time to play with the antenna modeling programs.

As you might discern from the above, I have as many questions after yesterday's experiments as I had before them. The AntennaSmith showed good curves on the three bands. The antenna seems mechanically solid. It is about 8.5 pounds assembled (less mount) which is about what I expected. But, the performance was puzzling.

Finally, with all this antenna talk I've nearly forgotten to mention the other thing that got a shake-out yesterday: my backside. {grin} I attended Contesting University at Dayton this year and one of the points that was made repeatedly was if you want to win you have to keep your butt in the chair! I did just that yesterday. It was a 10 hour contest and I was in the chair all but maybe 10 minutes of it. (I refuse to do the waste dump in the bucket. I'm committed, but I have limits!) There is no way that I'm going to stay in the chair for all 48 hours of CQ WW, but I found working this 10-hour shift to be easier than I expected. And, as shown above, I was rewarded with my best score ever for this contest. So, though I obsess about all this equipment in this blog, it is important to remember that the most important component to your DXpedition is you and the commitment you bring. Just two months to go. I can't wait!


Blogger Richard said...

This comment has been removed by the author.

August 19, 2007 9:23 PM  
Blogger Richard said...

If you only lost 10 minutes for bio breaks in a 10 hour contest, that's only 1 minute per hour! I too have my limits, so that seems like a small price to pay for not needing a bucket! :)

Rich AB1HD

August 19, 2007 9:25 PM  

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