First signals from AAUSAT-4

Today I woke up early to receive the signals from AAUSAT-4 as it passed over Spain for the first time. This satellite was launched from Kourou yesterday at 21:02UTC into a Sun-synchronous orbit. The main payload for the launch was Sentinel-1B, a 5GHz Synthetic Aperture Radar satellite from the Copernicus project of the ESA. The remaining satellites that were launched by the Soyuz rocket were Microscope, from the French CNES, designed to test Einstein's equivalence principle and the three cubesats in the Fly You Satellite! program: OUFTI-1, from the University of Liège, which carries a D-STAR amateur radio transponder, e-st@r-II, from the University of Torino, and AAUSAT-4, from the University of Aalborg, which carries an AIS receiver. Since the launch was into a polar orbit, the first pass of the Fly Your Satellite! cubesats over Spain was at 05:42UTC today.

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Outputting the crystal oscillator directly in the Si5351

I'm using a OCXO/Si5351A kit as an external 27MHz reference for my LNBF-based 10GHz receiver. At first, I intended to use a buffer amplifier to take out directly the 27MHz cyrstal oscillator in the kit. However, I finally configured the Si5351A to generate 27MHz, as that was simpler.

Taking a look today at the documentation for the Si5351, I've realised that it is possible to configure the Si5351 to connect some of its outputs directly to the crystal oscillator input, acting as a buffer and bypassing all the frequency synthesis stages. To do this, XO_FANOUT_EN, which is bit 6 in register 187 "Fanout enable", must be set to 1. The selector CLKn_SRC, which is bits 3 and 2 of clock control register (registers 16-23), is set to 00 (XTAL source) on reset, so this is already set correctly. It is probably a good idea to set CLKn_IDRV to 11 to get the highest drive strength on the output pin.

Adjusting TX gain in the FT-817ND

If you've been following my latests posts, you'll know that during the last V-UHF contest I detected reduced output power on the 70cm band in my FT-817ND. The output power was only about 60% of the maximum 5W in SSB and CW, but in FM mode it reached 5W. This problem only happened on the 70cm band. On all the other bands, the radio reached 5W output power in every modes. After spending some time studying the service manual, I came to the conclusion that the problem was that TX gain in the UHF band was too low. This is a software calibration parameter, so, in the end, fixing this problem has been rather easy.

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Replacing the fuse F1002 in the FT-817ND

On last Saturday's V-UHF contest I observed reduced output power on the 70cm band in my FT-817ND. I spent the next day poking inside the radio with the oscilloscope trying to see where the problem was. While doing this, at some point I completely lost output power in all bands. I found that the problem was that F1002, an SMD fuse, had gone open. Here I describe said fuse and the replacement procedure, which I found much easier than I thought.

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Concurso Costa del Sol V-UHF 2016

Yesterday, my father and I hiked to Cerro de San Pedro, SOTA summit EA4/MD-020 (1425m), to work QRP in this month's national V-UHF contest: Concurso Costa del Sol. Since the forecast for Sunday was rainy, I decided to go up on Saturday's afternoon. The summit is a short hike from a nearby road. We arrived to the summit around 14:25UTC, so I could work in the contest for a bit more than two hours until we started packing at 17:00UTC before it got too dark.

Activity seemed a little low, although this is not surprising, given that the national RTTY contest was also running at the same time. I also get the impression that there is more activity on Sunday mornings. Nevertheless, my results have been better than in March's contest. I did fewer QSOs, but got more points and worked more DX. In fact, I could work almost everybody I heard. In the map below, as always, my location is marked in red, the stations in blue are those worked only in 144MHz and the ones in green where worked both in 144MHz and 432MHz.

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