23 cm Beacon monitoring: IC-9700 with minimalistic antenna

2021-11-18

Complainment about the need of having an elevated location and large antennas to become QRV on 23 cm with an IC-9700 inspired me to compare my regular equipment of:

  • Flex-1500
  • TV 144 MHz
  • TV 1296 MHz
  • LNA 0.35 dB NF
  • 3 m EcoFlex 15
  • Ringfeed
  • 3 m dish on top of the mast

with my IC-9700, usually in use for 2 m and 70 cm and a minimalistic antenna:

  • IC-9700
  • 5 m RG213
  • Ringfeed for 1296 MHz, just on a metal step on the roof

The dish in the upper right and the ringfeed to be seen in the lower left on the metal step, both beaming south. As signal source the beacon HB9BBD/B on 1296.050 MHz has been chosen, 323 km away, on the Rigi Scheidegg in Switzerland, 1670 m above sea level. It is transmitting 10 w into an array of 3 dipoles beaming north.

As the whole air space between Mainz, JN49CV, and Rigi Scheidegg, JN47GA26, is visible, a lot of reflections on airplanes can be expected.

The signal of HB9BBD/B is very strong in Mainz, 40 dB over the noise usually. The gain of the dish is estimated to 28 dBD. The gain of a ringfeed may be 2 dBD and as it has just been layed down on a metal step on my roof, I assume the difference to be more than 30 db.

As expected, the signal could be received with the IC-9700 as well. It is deep in the noise, but increasing, when airplanes cross the path, audible most of the time.

Wide Graph of WSJT-X is a nice tool to display weakest signals and I very often use it to monitor distant beacons. I recommend it to anyone, who want to start beacon monitoring.

Deep in the noise is the signal at the ringfeed and the IC-9700 at about the same time as on the screenshot before. But it is always there and many reflections can be seen, increasing the signal level. Interesting is that different reflections dominate in the two screenshots. That is caused by the different beam widths of the antennas.

The conclusion is, that there is no point of not to try on 23 cm with an IC-9700 and asmall antenna. In this example the difference of the receiving systems is assumed to be more than 30 dB. When using a LNA and a 3 m yagi with the IC-9700 the difference will be not more than 10 dB, resulting in 20 dB stronger signals.

Aircraft scatter relativizes the disadvantages of locations in valleys and urban areas.