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UHF-Satcom.com - Ka-Band monitoring - Updated: (04/05/2009 19:07:42 +0100)
Update 14th April 2009 - Since the launch of the Kepler space-craft, some effort has been expended in putting together a 32GHz down converter from commonly available parts.
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The photos above show two views of the down converter assembly that is mounted at the dish feed. A scalar feed and associated 32GHz circular waveguide transfers the signal to the down converter unit which came out of a microwave link. On the back of the down converter are the DC-DC converters for FET bias as well as -24VDC generation for the phase locked oscillator. In this system, the local oscillator runs at 34.2GHz and high-side mixes, giving an IF in the region of 1GHz to 2.5GHz. The LO is derived from a 111.0389610MHz reference, which is multiplied up 308 times to reach the final LO frequency. The 111MHz reference is GPS locked for stability, and results in around 40-60Hz of signal wander at 32GHz. Sun noise is detectable albeit at very low levels of noise increase.
Update 4th May 2007 - Some time has been spent looking for Ka band signals from Skynet-5A and Syracuse 3B, none have been found yet. If you know the beacon frequencies for these satellites, please contact uhf-satcom using the details on the home page. Any other Ka-band beacon frequencies are welcome also.
Update 24th September 2006 - Ka LNB has now been chopped in half to produce two LNA units. The LNA has retained the existing Ka band feed, and now provides LHC and RHC outputs on SMA connectors. Useful gain has been measured from 17GHz to 22GHz. The pictures below show the modified LNB.
 Front view showing the Ka feed horn and 2X SMA outputs. |
 Back view showing RF screening assembly. |
Ka-band LNB now arrived - pending modification to use the LNA stages. Click on the large LNB picture to show the voltages and control points in the LNB. After careful study of the LNB design, it may be useful to know that the LNA stages should be useable at 24GHz.
 2 X Ka and 1 X Ku LNB from DirecTV. |
Click images for full resolution pictures.
2 X Ka and 1 X Ku port with septum feed |
 (above) Block Diagram of Ka-Band down converter. |
 (above) Ka-Band converter under test |
The block diagram above shows the basic concept of the converter - the local oscillator is generated from a 10MHz GPS locked oscillator, which is then multiplied up to 20GHz, resulting in a DC to 2 GHz IF. The 20GHz LO is generated with a modified M/A-Com phase locked oscillator, which generates 5GHz from a 100MHz reference. This 5GHz signal at around +10dBm is fed to a Celeritek X4 multiplier, resulting in a local oscillator signal at 20GHz (10dBm). The incoming RF signal, is mixed with the 20GHz local oscillator to give an IF in the 600MHz to 1.8GHz region. For testing purposes, the local oscillator has been set to 19.1GHz.
The IF is amplified using the usual MAR-6 specials, and fed to a communications receiver, which is also locked to the same 10MHz GPSDO as the local oscillator chain. Note: The AOR 8200 shown in the picture below was used for initial testing - this receiver is not locked to a GPS frequency standard. The receiver was used as an alignment aid for peaking the dish on the satellite. Since UFO-9 moves a few degrees in elevation, hourly peaking sessions are needed.
UFO-9 suffered an anomaly starting at 12:30z on 31st August 2006. The actual 20.7GHz beacon disappeared a few minutes after its initial anomaly. The satellite is now in a graveyard orbit and has been identified visually to confirm this. This satellite was a handy 20.7GHz test signal! The UFO-2 satellite which takes over from UFO-9 does not have any Ka capability for GBS or beacons. UFO-9 is listed as an uncontrollable space asset - its probably beyond recovery and should be considered inactive.
Some more info on GBS / UFO-9 is available on the restricted access pages.
 (above) Ka-band down-converter in test phase - listening to the GBS beacon from UFO9 |
 (above) Ka feed with AA battery for comparison.
(above) Ka feed and LNA on the dish! |
The front end now in use is a Direct-TV Ka band LNB that has had the oscillator disabled, and a SMA socket fitted to take the amplified 20GHz signal out. This is then fed via semi-rigid to the mixer as described above.
Ka band sky survey - 50 east to 50 east.
Satellite RF Freq IF Freq Modulation Position MHz MHz (19.1GHzLO) characteristics =========================================================================== Sicral-1A 20250.000 1150 Beacon with BPSK 16.1E 20914.800 1814.8 1MHz wide PSK Sicral-1B 20250.000 1150 Beacon / continuous carrier 13.3E Hotbird-6 19700.982 600.982 Beacon 13E 19729.18 629.18 Transponder 19748 648 Transponder 19748.36 648.36 Transponder 19825.08 725.08 Transponder 19842 742 Transponder 19844.26 744.26 Transponder Eutelsat-W3A 21404 TBA Beacon 7E 21462 TBA Transponder 21587 TBA Transponder Syracuse-3B 20249.976 1149.976 Beacon / continuous carrier 5.15W UFO-9 20699.994 1599.994 Propagation Beacon + FHSS Modem (carriers +-203.5KHz) 22.5W 20295 1195 Transponder QRT from 12:30z on 20415 1315 Transponder 31st August 2006 20475 1375 Transponder 20595 1495 Transponder (DVB GBS downlink - CNN & Fox news)
(above) 20699.994GHz (20.7GHz nominal) beacon from UFO-9 at 22.5 degrees West. Note in the FFT, traces of a FHSS modem can be seen.
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(above) The four photos above were emailed to uhf-satcom.com by a person wishing to remain anonymous. They are supposedly from a Ka band satellite over the USA (later confirmed as UFO-9's GBS transponder).
