The active frequencies are stored in the scanner memories (Figs. I found my local active frequencies by scanning the air/marine bands and searching online. The amplifier covers 47-826MHz, and the gain is set to ‘low’, to prevent overloading the scanners.
“A dual-band 144MHz/446MHz antenna feeds the scanners, via a 4-way wideband TV amplifier.
My monitoring station on the Rock has three scanners a Uniden UBC355CLT monitoring the 446 PMR channels a Realistic PRO 2021 scanning the marine band and a Realistic PRO 2045 for the air band. Kev writes, ‘Gibraltar, being surrounded by water on three sides and having its own airport, has very active marine and air bands. It is great to hear once more from Kev Hewitt in Gibraltar. “An overview of current spacecraft, which can be received can be accessed at this URL: “We have a Yahoo Group for coordinating Amateur DSN activities, discussing microwave hardware and so forth. 2) of a signal I received, from the YUTU Lunar Rover, which landed on the Moon on the 1st December 2016, and which was tracked by amateur observers from shortly after launch. However, a 1.2m offset would be a great start for some of the closer spacecraft. A diameter of two to three metres is ideal. The old saying of ‘bigger is better’ certainly applies in this case, and you should use the biggest dish antenna you can reasonably get away with.
“Usually it is possible to get within a couple of kHz of a downlink frequency, enabling you to use a narrow span (10-20KHz) in your software radio application to visualise the signal. This is measured in km per second and can be fed directly into my frequency calculator spreadsheet to provide the correct tuning frequency. The Horizons tool mentioned above provides the ‘delta-dot’ parameter or range rate. For other spacecraft, such as those in orbit around Mars, the relative velocity can alter dramatically. For spacecraft like STEREO-A, the shift is small because the spacecraft is operating in the same orbital plane as Earth. “Since the spacecraft we are interested in tracking, are moving relative to the motion of the Earth, there will be a Doppler Shift.
Once you have apparent azimuth and elevation figures in 5-minute intervals, it's very simple to align your dish with a compass and precision elevation level prior to full automation here, I used this technique for 13 years! This can be automated, once your station is established and offers ‘point-and-click-DX’.
“This allows monitors to enter key station data (latitude, longitude, height above sea level) and compute accurate pointing data for any spacecraft, planet, asteroid and so on. Antenna pointing is another interesting area and has been made significantly easier with the availability of the JPL solar system dynamics tool ‘ Horizons’, at this URL: “Frequency standards are a huge area of interest and it's easy to become fanatical about accuracy. As a fall-back, a GPS-disciplined rubidium oscillator is available. The entire converter’s frequency reference comes from a shack-based 10MHz source, which is locked to GPS timing and is therefore extremely accurate. Figure 1 shows my downconverter, currently in use for receiving Deep Space Network (DSN) spacecraft. “There are a number of solutions that can help here, mostly with off-the-shelf GPS locked-frequency sources.
Frequency stability and accuracy is extremely important often you will be looking for a signal in a few kHz of bandwidth at 8.4GHz, and this may be a dB or two over the noise floor you will have ‘antenna pointing uncertainty’ to factor in as well, so it's worth addressing frequency stability and accuracy. “Some technical knowledge will be required to build and optimise the Low Noise Amplifier (LNA) and down-converter. Paul continues with his explanation of what’s involved: Readers who were ‘with us’ last month may remember that Paul Marsh had kindly shared some information about his station for tracking spacecraft in deep space. If you haven’t emailed so far, then please do – it would be really great to hear from you. Thank you so much to those readers who have taken the trouble to introduce themselves and write with details of what they enjoy listening to! It’s fascinating, and I have already learned plenty and have been inspired. This month, scanners enthusiast Tim Kirby continues his mini-series on receiving signals from deep space, reports on scanning in Gibraltar and revives an old Yaesu VX-1R.