UHF-Satcom.com - Ka-Band monitoring - Updated: (18/03/2015 19:45:21 -0000)

The picture to the left shows the HughesNet LNB. This unit was from eBay, and is actually really great value for money. The LNB was intended to work in the 19.7GHz to 20.2GHz band for satellite based Internet, as part of the 'WildBlue' systems which are sold in the USA and Canada. The DRO operates at 9.75GHz is filtered and fed through a Wilkinson divider to the 2 sub harmonic mixers. The LNB is dual polarity and is switched with a 27MHz signal applied to the IF output. The RF devices are p-HEMTs from Mitsubishi and NEC. Front end NF is around 1.2dB at 20GHz.The oscillator can easily be retuned to 19.2GHz, giving a coverage of 20.2GHz to 21.2GHz, with virtually no loss of input sensitivity, despite a band pass filter being in place. The dimensions for the waveguide input face of this LNB can be found here. There is a reasonably high resolution picture of the LNB's PCB here.
Another modified LNB is the Inverto unit originally intended for Saorsat in Ireland. The modification here includes the removal of the bandpass filters for each polarity, and the addition of an LO injection point. This allows the full Ka band to be covered. IF gain is good from 600MHz to 2.5GHz.

Ka band sky survey - 80 East to 60 West.17.3GHz to 22GHz

Satellite		RF Freq		Modulation
Position / Name		MHz		characteristics
72.5E			20295		Transponder
UFO F-10		20415		Transponder
			20475		Transponder
			20595		Transponder
			20700		Beacon

60E			20700.000 	Beacon, TT&C on +-1024kHz of centre, carriers +- 2048 kHz of centre
WGS 2			20847.275 	Multiple Carriers, poss. ranging tones
			20870.705 	Multiple Carriers, poss. ranging tones

52.5E 0032		20201		Carrier
Yahsat 1A		20202		Carrier
			20390		QPSK data 27MHz wide

47.7E 0135		17.810014	TT&C
PAN 35815		20298		Carrier
			20402		Carrier
			20700		Carrier
			21102		Carrier
			Note: This satellite transmits some massively wideband data which appears as a huge lump of noise
47E 0074		20245		Carrier
Syracuse 3A 		20870		OQPSK 2500Ksym
			21083 		FHSS OQPSK 8MHz wide
44E 0094		17810.065	TT&C

37.8E			18705		QPSK - 10000Ks/s DVB-S2
Athena-Fidus		18790		QPSK
			20171		RCS type traffic
			20200		Beacon
30E 0210		20700		Carrier
Milstar 5

24.8E 			19704		Carrier (part of TDP5 propagation experiment)
Alphasat		39402		Carrier (part of TDP5 propagation experiment)
23.5E 0268		20199 V		Carrier 28 dBW average EIRP
Astra 3B	

20E			20250 		BPSK 2Mbps Encrypted.
16E			20250		Beacon + TTC
Sicral 1		20899.750	Carrier
			21041.750	PSK
			21042.775	PSK 500KHz wide
			21093.275	UHF TPX loop - Downlink from 293.275MHz uplink
			21108.175	UHF TPX loop - Downlink from 308.175MHz uplink	
11.99E 0387		20250		Beacon + TTC
Sicral 1B		20535		DVB-IP data 8682Ksym, FEC 1/2 - Network Name: Selex EHF Beam. 		
			20660.190	OQPSK 2000Ksym
			20855		DVB data

9E 0418			19995		QPSK
KA-Sat			20120		QPSK
			20185		QPSK 25031Ksym

7E 0438			21404		Beacon
Eutelsat-W3A		21462		Transponder
			21448.35	QPSK 1724Ksym
			21449.65	QPSK 1900Ksym
			21539		QPSK 1714Ksym
			21564		OQPSK 2857Ksym
			21567		QPSK 714Ksym
			21580.85	QPSK 2480Ksym
			21586.5		QPSK 1860Ksym
			21599.1		QPSK 1500Ksym
			21587		Transponder

5.15W 0584		20249.971	Beacon / continuous carrier
Syracuse-3B		20762.375	200KHz wide PSK

7.5W			19700.982	Beacon	
Eutelsat 8WC		19729.18	Transponder
			19748		Transponder
			19748.36	Transponder
			19825.08	Transponder
			19842		Transponder
			19844.26	Transponder

12W 0672		20219		DVB data
WGS-3			20251.200	QPSK 1048Ksym
			20310		DVB data
			20700		Beacon, TT&C on +-1024kHz of centre, carriers +- 2048 kHz of centre
			20735		DVB data
			20780		DVB data
			20829.396	QPSK 2048Ksym
			20836.600	QPSK 2048Ksym
			20838.425	QPSK 348Ksym
			20843.120	QPSK 2079Ksym
			20889.500	OQPSK 2500Ksym
			20899.775	QPSK 1.2MHz wide
			21097.27	Beacon
			21161.500	QPSK 2.5MHz wide
			21196.23	Beacon

22.5W			20699.994	Propagation Beacon + FHSS Modem (carriers +-203.5KHz)
UFO-9			20295		Transponder 
QRT from 12:30z on 	20415		Transponder
31st August 2006	20475		Transponder
			20595		Transponder (DVB GBS downlink - CNN & Fox news)

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.

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.

The current Ka band "LNB" is shown to the right; (You can click the picture for the full sized version). The LNB consists of a ~5GHz phased locked oscillator from M/A Com, the output of which feeds a X4 multiplier.

This gives an LO around 19-21GHz. The LO is fed to a mixer / IF amplifier that came out of an old DMC microwave link operating at 22GHz. The input filter has been suitably modified and the IF section completely replaced with a pair of MMIC broadband gain blocks. The entire unit runs from 24V DC.

The 'front end' is the usual Direct-TV Ka band LNA.

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.

(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.

(above) The four photos above were received from UFO-9's GBS transponder.