Monday, March 10, 2014

Pondering the Unknowable

There are events like Field Day and Jamboree On The Air, JOTA, that you might be willing to invest more time on an antennas and run more than QRP. I had an opportunity like that this Saturday at a local home show. In  short, I used the Icom 7100 between 20 and 40 watts and an elevated doublet using the SGC 237 Tuner. It was handy to remote the tuner and the antenna from the operating position. I was able to sustain ops at that level for about 4 hours on a 15 AH LiFePO4 battery. The battery had plenty of juice left as I only used 6 AH but the 7100 started shutting down due low voltage around 11.5 while tuning.  I looks like operating on battery for Field Day with the 7100 would be tough. Note, I did get through the entire Field Day last year with the KX3 and the same 15 AH battery.

Likewise, would I have done about as well with the Alexloop as the elevated doublet. I did operate at the home show last year. I looked back and I had about the same rate of QSOs with the KX3 and the Alexloop. So are the extra power and the more extensive antenna worth it? The answer is unknowable, but I rarely feel that I did better with the extra power and larger antennas. I think there is a level you might reach where you command the frequency with a amp and a beam. But if you are hunt and peck the rate is pretty constant.

I see operating as a continuing series of imperfect experiments. Based on these experiments I can make my choices for future operating opportunities. In fact, for the April 5th RaDAR contest I am going with Alexloop exclusively while last year I used end feds antennas and  a 31 foot poles. This will minimize setup time and will be easy to transport by foot the required one kilometer between locations.

In any case, I enjoyed operating outdoors at the Home Show and the weather was nice. The antenna setup was fun. The bleachers helped get the 44 foot doublet about 45 feet high at the peak. The doublet was made from 300 ohm feedline and split for 22 feet on each side. The SGC 237 at the bottom of 31 foot Jackite pole. Then 70 feet of RG8X to Icom 7100. The doublet tuned fine 30 meters and up but would not tune 40 meters. 6 AH was used over four hours for 16 QSOs using between 20 and 40 watts. The rig started shutting down on transmit at key down to tune volts about 11.5. Battery had lots of life left with voltage at 13 volts on receive. So I switched to KX3.

20 QSOs:
30m CW 1,
20m CW 3,
17m CW 1 SSB 3,
15m CW 6 SSB 1,
12m CW 1 SSB 1,
10m CW 1 SSB 2.

DX Canada, Netherlands, Hungary, Puerto Rico 2. 
States MO 2, NJ 2, MA, MN, MI 2, TX 2, ID, NY, VA and KS.

Oh yes I had a relay QSO with Marcus NX5MK via KD2AJT Louise. His Alpha Loop was doing well to NY.

44 foot doublet

SGC 237 Tuner

Icom 7100

Last year's setup for Home Show