10 GHz SUN NOISE MEASUREMENTS 20 July 1996 Vernon, CT N1BWT & N2LIV Solar flux: 68 at 2800 MHz 219 at 8800 MHz 498 at 15400 MHz Calculations of antenna efficiency are using solar flux interpolating between 8800 and 15400 MHz using the program NOISE version 2 by Mel Graves, WR0I. Estimated receiver noise temperature (Te) = 230K, with a high confidence that 188K < Te < 250K. Antenna efficiencies are shown in paranthesis for the first few entries to show the effect of this range of noise temperature. Call Dia. Feed Sun Noise Antenna Efficiency Te = 250K ----- --- --------------- ------- --------- N1BWT 30" mod. Chaparral 3.5 db 65 % (54-71) K2STO 48" [*]W2IMU dual mode 3.2 21 % (18-23) [Note: dish f/D~0.4] N2LIV 31" [*]Chaparral 3.0 48 % (39-52) KG2BB 28x40"offset rect. horn 4.2 73 % est 32" equiv? N2OBH 30" [*] (?) 2.9 48 KD1DU 22" [*]Chaparral 3.0-4.2 [bogus] N1BWT 18"offset rect. horn (QEX) 3.3 [bogus] N1BWT 18"offset Chaparral offset 1.6 63 N2LIV-2 30" [*]mod.Chaparral 3.0 51 KD1DU 30" [*]Chaparral 3.0 51 N1RDK 48" [*]4-ring Chaparral 5.9 57 WA1MBA 24" [*]Prodelin 1.0 21 K2RIW 33" [*]Chaparral 4.3 71 N2UZM 24" [*]Chaparral 3.5 [bogus] N1BWT 25" Chaparral 2.6 61 N1BWT 18" Clavin 1.9 63 KH6CP 24" Homebrew Chaparral 2.6 65 N1BWT -- std. gain horn (43%) 0.6 [*] includes feedline - see Comment 5. COMMENTS -------- 1. Measuring sun noise is difficult in a paved parking lot with cars and people around. The pavement seems to reflect much more than grass, which seems to behave more like a black-body radiator at ambient temperature. On the pavement, it is very difficult to get a good ground noise reading to calibrate the receiver noise temperature, leading to the uncertainty. 2. We also had some problems at this gathering with folks demonstrating their transmitters, etc, and possibly other interfering sources, leading to bogus readings (efficiency >100%) for a few antennas. Apologies to those whose antennas were unable to have good measurements. 3. Results were very encouraging. Even with measurement uncertainty, we should consider an efficiency around 50% as good performance, and efficiency over 60% as excellent performance. Almost all the antennas were good or excellent, and the others learned that they need to improve. 4. The lowest efficiency measured was a commercial antenna from Prodelin. This should be a reminder that commercial antennas are not always designed for maximum gain and efficiency, so finding a complete commercial antenna is NOT a guarantee of good performance for ham communications. 5. Some of the antennas included a feedline, such as a "Shepherd's Crook" arrangement, while others were measured at the feedhorn. Adding feedline loss to the others would reduce gain and system efficiency.