Category Archives: EB3FRN

Retuning the DMC DRO locked oscillator to use as LO in 24GHz

Now I’ m looking retune the DRO locked oscillator modules to 23616MHz to get a IF of 432Mhz at 24048MHz. To get 23616MHz I can use 98.4MHz (x240) and 105.42857MHz (x224). As I have a xtal of 105.43857Mhz I wish use the same in the two units, but have in one unit dosen’t works.
The unit that originally have a xtal of 99.04MHz dont accepts xtals more high than 100Mhz, and the units that originally have a xtal of 105.99MHz dont accepto xtals of less of 100Mhz. Comparing the units, looks that the issue is in the wire inductors located near of the xtal.

DMC DRO locked oscillators opened

DMC DRO locked oscillators

To check the reference inside of the unit exists a SMA located in the upper right that gives the ref freq x4. After modify the coils now and retuning the filter located in the bottom right , the unit that only accepts xtals up to 100MHz locked now can be used with the 105.43857MHz xtal.

DMC DRO locked oscillator test

DMC DRO locked oscillator xtal

New 24GHz toys

Recentlly I purchased some DMC microwave modules tu build a 24GHz transverter. This modules are designed to work at 22 / 23GHz but can work well at 24GHz with a minumum work and be purchased in ebay.

24GHz DMC modules

The set is composed by a DRO locked oscillator, upconverter, downconverter and LNA. The DRO locked oscillator, uses from 90 to 110 MHz as reference. The upconverter uses a 310MHz IF input and outputs over 15dBm ( 30 mW). The downconverter have a IF output of 1.4GHz, and have a second donwconverter to convert from 1.4GHz to 70Mhz. Finall the LNA have over 15dB of gain and a NF over 2.5dB / 3dB

24GHz DMC RX test

All the modules use 8.4V dc except the LO that uses 8.4V and -5V. Googling a bit, I found some info about the modules:

http://www.xertech.net/Tech/DMC/DMC_main.html

http://www.qsl.net/w6by/parts/dmc.html

http://af4jf.blogspot.com.es/2012/06/even-more-24ghz-toys.html

http://af4jf.blogspot.com.es/2012/07/power-supply-for-dmc-modules-24ghz.html

Ephemeris for planetery space probes

The next images, I’m comparing the data using my ephemeris in the upper side and Horizons ephemeris in the lower side. Remember that Horizons dont give data for planetary probes, and are using the data of the planet that is orbiting the planet.

Data for Mars Express

As you can apreciate, in the upper side, the range calculated using SPICE and the mission kernels is smaller than the range of the MARS calculated by Horizons. Then the MEX space probe not is eclipsed by the planet and then detectatble for our stations in the earth! Check the difference of 60 KHz in the predicted frecuency and doppler too.

Data for Mars Reconnaissance Orbiter

Now the inverse case, the MRO probe is more away from the earth, then the probe is eclipsed by the planet.

Another issue observed is a small position difference from JPL/Horizons to my ephemerris using SPICE. It happend, because JPL/Horizons uses TDB as time reference and I’m using UTC. Then, exists a difference of few secconds produced by the leap seconds.

Cooking epehemeris at home

As I was write in my last post, one of the challenges of the amateur-DSN stations is get the ephemeris of the space probes to get the position and deldot for the doppler. JPL Horizons helps, but dont give info about the planetary space probes. How solve it? The solution is use the same data and tools that are using the mission control 😉 Every mission, have a dataset called kernel that contains info about position, instruments and clock onboard, mission operations, etc… this data is public and is controlled by NASA / NAIF and can be obtenied from here.

JPL / NAIF website

The Nasa NAIF, proces a toolkit called SPICE to use this data. This toolkit is available in a lot of programming languages and have a good documentation. Using a small piece of code from Achim Vollhardt DH2VA that he was send-me in 2006 and after some years googling a lot, finally I build my own planetary probes ephemeris generator.

Spice tookit code

In the next post the results…

The JPL Horizons ephemeris system

One of the challenges of the amateur-DSN stations to track planetary and solar system space-probes is the position and frecuency accuracy. Currently all the stations are using the ephemeris provided by the JPL Horizons system. This is a cool system and can be used online using telnet, using a web interface or via email and provide-us the position, range and deldot of the select target, then using this data can track easy the probes and calculate the doppler.

JPL Horizons

Due that the JPL Horizons is a service for the main public basically for amateurs and space anthussiastas, they can not provide ephemeris for probes or missions that are orbiting a planet because this kind of missions not are static and depends of the stage of the mission.

The solution provided by Horizons is track the planet is orbiting the probe, for example to track MRO, MEX and MO have to track Mars. It works because the position difference is minimal, a typical difference of less of 0.05 deg and it not makes a sense in our small dishes. The amateur-DSN members are detecting space propbes that are orbiting a planet during years with good results, but we have some troubles like taht we dont know when the probe is eclipsed by the planet and, and we dont know the exact frequency where is the probe, because the probe and planet have a differnt deldot. Now I’m working in generate my own ephemeris, to get the data of the probes that are orbiting planets.

A interesting issue about Horizons that I discovered recently is that dont give the data in UTC time, it gives the data in Barycentric Dynamical Time.

New mixer for the 8.4 GHz downconverter

Today I continued updating the downconverter for X-band deep space probes. Having the local oscillator selected, today was the mixer selection. Up today I was using a RHG mixer purchased in 2006, but from the 2006 up today I purchased another units, but not tested up today.

RF Mixer testing, test setup

After test the 5 units, looks that I have a unit perfect for 8.4 GHz 🙂 it is a Aertech 8500 this mixer look more of 4 dB better that the RHG mixer used up today.

RF Mixer comparation

Now only need check the low noise amplifier to see the performance and decide if I build a new one. I’m very anxious to receive space probes again!

This weekend 24GHz !

In the middle of 2009 I bought a 26GHz transceiver to use in amateur-DSN. It was to try to receive the 25GHz downlink of the Lunar Reconnaissance Orbiter spaceprobe. After much time without succes and after the confirmation of Paul J Marsh, that he never has received the probe too I decided give a new life to the module and try to use in 24GHz amateud band.

Thales TGTR-26 trasnceiver

The module is a THALES TGTR-26 and googling a bit, looks the some Autralian amateurs are using the module without problems. The first was get a suitable local oscillator , this unit should accept a frequency range from the 10 to 14Ghz. The idea is ise a IF of 1.3Ghz then need a LO over 11.45Ghz. Using the cavity and electronics of a Magnum MC PLS22 that accepts 10MHz input reference and the SRD and output filter of a Magnum MC PLX31 that cover from 10.4 to 10.7GHz, I put all totgether and after retuning the SRD I get a nice brick of 11.36 GHz, pefect to use as LO.

Magnum brick oscillator

The TGTR-26 uses +5V (1A),-10V and +8V to enable the TX branch. One time solved the power issues, the unit was start to receive very well, giving a conversion gain of 29dB aprox. To test the RX branch I was use the Marconi / Aeroflex 6203 microwave test set as signal reference.

RX Test setup

Marconi 6203 tuned at 24.050GHz as RX reference

Marconi 6203 tuned at 24.050GHz -90dBm

IF at at 1.3Ghz, signal at -63dBm

After to verify the good results of the RX branch, is the time of the TX branch. To put the transceiver in TX only need aply +8V in the TX pin. The result was amazing, receiving peaks of 32dBm, it can be more than 1.5W! This test has ben used a 10dBm IF at 1.3GHz.

TX Setup

Signal generator as TX IF

TX Signal plot

TX Image signal plot

The unit is suitable for amateur use in 24GHz. Really amazing how this modules that can be purchased in ebay and can be recycled to give a new life.

The PHI / Notcar SDR

One of my challenges is detect a pulsar using my small dish antenna. The pulsars are vey weak radiosources and not easy to get for the amateurs, maybe be the most difficult signal to detect. The only way to detect the strong pulsars with my antenna is using a massive bandwith. Looking the sdr radios market dont find any radio that give-me more than 20Mhz of BW inside of the PC to process it, the trouble is the bootleneck is the USB and Ethernet. But in the middle of 2012 appears a new sdr radio called PHI from a young canadian company called Pervices. Looks that can give me the bandiwth that I need to detect pulsars.

The PHI / Notcar is a 8x PCI-E with two 125Msps ADC and one 250Msps DAC handled by a Altera FPGA. The card gives up to 250Mhz of bandwitdh and a throughput of 5Gbps. The card have two RX branches one working in base band with real type signal ideal for IF, and a I/Q type signal in a direct conversion setup that covers up to 4GHz.

The PHI SDR card

The most important before to start the card, is get a very power PC. You will need a lot of horsepower to process the high samplerate that handle the card. In my case I’m using a Intel I7 3770k that is performing very well.

The first impression is very good, is a card with a lot of potentail, but is important to say that it not is a plg&play finished product, really is a open development platoform. To get good results, you will have to put a good rf frontend.

This are the screenshots of my firsts tests:

Full FM band, centered at 108Mhz

Digital TV signals at 660Mhz

I developed a small rtlsdr server tha handle any input, that I’m using to feed the SDR# from the PHI:

PHI SDR# setup

Here one of my firsts success, this a screenshot from a L-band Inmarsat satellite, showing in realtime from 1520 to 1560Mhz, getting more than 15fps:

L-band Inmarsat transponders

Now I’m learning to use Sigproc and Presto, to use it with the PHI.

Note: Recentlly Pervices has upgraded the PHI card with some new features, and now the card is called Notcar.

Phase noise tests in brick oscillators

After the dish controller rebuild, now I’m updating the X-Band downconverter.
One question that rounds over my mind some times is how good is the phase noise of the Ma/Com brick that I’m using in the downconverter as local oscillator. The last year I was puchase in eBay a nice Ferranti brick oscillator.

Phase noise test

The two units are locked to a 10MHz rubidium reference. After some tests and tuning, the Ferranti beats the Ma/Com, it is much clear:

Macom vs Ferranti PN

Test Seup

Dish Controller Rebuild

Starting the new season, I’m doing a lot of improvements in my system. Now I’m rebuilding the dish controller. The idea is get more mechanical precision and reduce the backslash. I hope improve the security too.

Dish Controller

The selection of the speed and motion of the linear actuators was controlled by a ADAM 4068 relay module. It has been changed by a ADAM 4052 Digital input/output module, to reduce the reaction time and reduce the backslash. Now the ADAM 4068 relay module is used as watchdog to stop all if the comunication with the linux server is lost. I added a Emergency stop push button to the controller box.

Inside Dish Controller

Finally I added a RFI EMI power line filter and some ferrite core filters to reduce the RFI noise that was generating the controllner in HF.

Wind test: PASSED !

Currently I live in a nice rural village at 100KM from Barcelona. It is a clean RFI zone without strong near transmitters. This area is very good for weak signal radio like Radio Astronomy, Seti and EME activities, except for one point: the wind.

Wind peak from 2009 to 2013

Every January strong winds appears here, getting every year peaks of more than 100Km/h. But in 2009 we was get a explisive cyclogenesis with winds of more than 150Km/h destroying my 10 foot dish completely

10 foot dish destroyed

After the destruction, the idea was mount a new dish and mount capable to support very strong winds. Thanks to Paul J Marsh I was get the contatact of a Denmark guy that was sell me a professional Non-Penetrating Roof Mount, and from my friend Joan Coll I was locate a Prodelin 1251 dish here in Spain.

New dish mount

Prodelin 1251

This week, as every January we have get strong winds again getting the levels as in 2009. I was very worried about if the strong wind can damage the new dish.

Evolution of the wind in January of 2013

Well, one time the cyclogenesis has passed, the dish has not been damaged and it is in good shape! 🙂

After the storm comes a calm 🙂