SM5LE , 1296 MHz , pictures .   Updated : 13 Apr 2008            Back to  SM5LE Homepage

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Power divider for driving two PA:s and include phasing lines in one (1) "channel".

To achieve 50 Ohm output from the phasing lines I did use an isolator.

The output is apr. 2x20 W @26V and 4.5 A.

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My Sun Noise measurement apparatus.

The Sun Noise is measured on the cable coming from the LNA housed in the dish head.
I am using isolators on both cables , to LNA and for input on RX (TS-2000x) , as they not have a good 50 Ohm (I assume).

The Attenuator need to see 50 Ohm otherwise it shows not correct value. Also I am using a huge panel meter to easier read exact spot.

The panel meter is connected to a HP 400FL AC voltmeter ; connected to the speaker on TS-2000x having full SSB BW ~5 kHz.

Of course AGC off and RF gain backed off to 14:00 a clock on the TS-2000x

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Avoid rotator cables to twist (when elevation) : Use "thrust bearing" for cable support to SPID rotator.

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With a 2.5 m long ruler , I adjust the dish for 90 dgr                             Then mechanicly adjust  the fiber-pole and Septum to (0) zero dgr

(try to do that on a 10 m dish - hi).                                                                                                                                                                       

Then , if the sun will shine for once , I can check if the shadow from Septum is in center of the dish.  ... but

no more sun-measurements , sun to low. Have to wait to next summer. The sun-noise is "covered" with man made noise in low sun-elevation :(=

Is my Septum in the dish center ? I just happened to notice that the shadow from the choke ring not was in center of the dish when max sun-noise occur. It has to be adjusted...

Azimuth OK but elevation has an offset ~3degrees ! No good ...

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 Happen to have an old IFR AM/FM 1500. Frequency only covers to 1000 MHz not to 1296 MHz. :-(

By using a mixing procedure it easily will do nice frequency measurements on 1296 MHz.

SM5LE can now measure the TX frequency within some 10 Hz when transmitting WSJT signaling. :-)

A frequency counter with digital readout goes crazy , can measure CW only.

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The final LNA pictures :

The cut from LNB soldered to the cavity.

The coax-switch and an extra relay to make the Coax-switch "PTT behaving" and one for "TX confirm".

All in a box made of Cu laminate (what else - hi).

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Now the "Super Trick" ;  How to match LNA1 to LNA2

Normally the LNA1 does not have 50 Ohm output and LNA2 not 50 Ohm input , they are just optimized for Gain and NF. Here is the trick how to make a good transformation in between LNA1 and LNA2.

By cutting the cable length in between LAN1 and LNA2 one can have Gain and NF optimized, at the same time as it is a connection cable for LNA1 and LNA2. I did cut the 50 Ohm PTFE double shielded coax (3mm in diameter) in one (1) cm cuttings! A rather time-consuming maneuver, but it relay paid off! The coax-cable was resoldered on a small patch.
The absolute cable length for your LNA´s , you have to finde out your self, this is only showing how to do it.

One can see that minimum NF and max Gain almust came at the same length. The shadowed part is when the whole thing did oscillate. The graph shows only that part of the cable that was cutted in between the two patches.
The total length in my case becomes 26.5 cm.
 

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Cavity LNA competition :

Very little benefit for the Ag cavity vs. Cu . "Hairpin" input of course came 3rd.

Maybe the Ag will last longer without oxidation. 1st place Ag cavity; Gain 20.2 dB and NF 0.30 dB and better oxidation stand ; 2nd place Cu cavity gain 20.0 dB and 0.32 dB NF and ;

3rd "hair-pin" input , Gain 17 dB and NF 0.4 dB.
And remember the 0.30 0.31 etc are very close to measuring accuracy...

Output coil 10 turns on 1mm diamater. FET marked "V".   Id 10mA  @  -Ug 0.55V
 

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mA vs Gain and NF for V=1.5V and FET marked "V", cavity input.     ( -Ug adjusted for the wanted mA).

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Cavity input LNA made from copper sheet and screening box parts.

Parts :  Polished copper 0.5 mm and parts from tinned screen box, top and bottom (30x30mm).   Height 40 mm.

Rod 30 mm , 9 mm diameter.

  All soldered together. Gain 20 dB, NF=0.31dB. FET marked "V". 15mA @ 2.5v -Ug=0.63V

 Tested also small inductance in-between output from cavity to input to FET.

 Tested also different resistance on output from FET.

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1296 MHz BP-filter made of dubbelside Cu laminate. Cutted and soft soldered together. Insertion loss < 1dB, ripple < 0.5 dB and +/- 8 MHz 3dB bandwidth.
The filter is from "InderDigitalFilter" software at VK3UM Homepage. The rods were shortened 20% (~5mm) to have more tuning range.
 

  50 MHz/10dB / div.

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Can I use a FET (HEMT) from an LNB ? Yes ! It  looks likely.   Here : some more FET-s tested  and L/C on output.

First I build a test board. As I am not a mechanic man I use double clad laminate and soldering iron. First a silver plated cavity cylinder and a feed trough capacitator in the bottom for the bias. (Yes , stolen idea - hi). This is NOT an exact building description, it is just how I do my tests.

And some laminate for walls

The input capacitance soldered on a SMA inner pin.

Laminate capacitor, from under- and from upside. Photographed trough a magnifying glass.  Diameter 10 mm . Teflon board 0.125 mm thick.

The laminate capacitor is long enough to pass the wall so the FET experiment can be done outside the cavity.

The top of cavity is fixed with M3 screws ( one wall still missing - hi). The SMA input connector has a soldered nut on inside so one can adjust the capacitance (the distance to the cavity cylinder).

The FET is taken from a LNB and cuted out as it is difficult to unsolder the FET itself, so why not take some laminate as well.

  The gate for the FET was first soldered with a small lead (only 1.5 mm) and the FET was lying (soldered) on the PCB ... BUT !

... the resonance frequency was 40 MHz to low !

Then I lifted the gate lead up in the air and no extra lead ... and see; it was on right frequency, 1296 MHz.

And this is what the NF meter showed !  NF 0.25 dB !

You have to subtract 10dB for the NF and add 10 dB for the gain as I have a 10dB attenuator (well calibrated) on the input. 

But remember that this is only a NF meter reading ...

  I think that the letter "L" stands for Mitshubishi MGF4310 series (GD-4  package).

  The test setup. More FET´s and "cuts" from LNB´s will be tested later on ...

Only 1st stage (one FET was tested).

The output cirquit is just a 10 wound  "HF-choke" to + Ud and 47 pf in series with output.

Some data : Uds = 2.0 V ,  Id = 12 mA @  Ug = - 0.33 V.

The cavity appr. 30x30x40 mm and cavity cylinder 30 mm and 6 mm diameter. Tuning cap input/and top 10 mm diameter.

Tnx to all hams that have given me materials and infos ! TNX ! Tnx to : WA6PY, SM0DFP,OK1DFC, JA4BLC and those ten I forgot - hi.

Most ideeas whas taken from "1296 MHz-LNA with cavity input" by DF5J/EA6ADW 1296MHz Low Noise Preamplifier and more from the WEB.

KEEP THE SOLDERING IRON HOT !

Some more "FET-cuts" tested.

By cutting the FET´s out it is easier to handel ... it is so small things nowadays ...

Here is some results :

 It looks like selection in the same type number area makes more NF improvements than looking for the best type number. If I buy an "up to date" LNB 0.2 dB NF I got this selected FET. For apr. 20 EU:s LNB I got 3 FETs, one for each polarization and one for 2: nd stage (selected ones).

Can enyone tell me what "Gd" and "Fe" stands for (Type nr), pse mail me.   /Sven SM5LE

No more FET´s to be tested.

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Did test different output coil (RFC to +V). Two different innerdiameters 1mm and 2mm was tested.  The test object : FHX35LG .

Did test different output capacitor (serie output)

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I did cut my 12cm deep choke ring down to 9 cm and measure Cold Sky vs. Ground Noise and Cold Sky vs. Sun Noise trying to find out what is best deep. The position behind rim was kept to 3.5 cm. No moon was available. Ring diameter 40 cm.

I did study Paul’s, W1GHZ, paper "Enhancing the OK1DFC Square Septum Feed With a choke Ring" 2007, to ensure what I was doing - hi.

It was very small amount of dB and difficult to get precise measurements, but this is the result anyway :

  I did stop at 9 cm.

The grounding for the ring is made of beryllium copper braid that makes it easy to move back and forth.

As the ring is made of copper and the feed of aluminum it is a "oxidation situation", but by using beryllium the "oxidation potential" are smoothed out a little (I hope - hi).

Ring position behind rim vs Sun Noise (SN) and Ground Noise (GN) was measured ( to cold sky). No moon avaible.

This curve shape  is close to fig 11 in the paper "Enhancing the OK1DFC Square Septum Feed With a choke Ring" 2007.    My f/D is 0.34.

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0.75 kg mesh septumfeed :

   Made of  :   Brass mesh , Cu epoxy laminate , Cu metal sheet.

 Not round not square, but an "eight (8) corners".   All soft soldered together...

  And backplane made of double clad epoxy laminate.

  Saw and dust making the septum wall.

  Leaving some epoxy strip to support the wall for stability.

   Back plane and septum wall soft soldered together. Note that the cons were not in final construction. Difficult to adjust length...

  And together.

  Instead off coons , I used monopoles with top cap.

  Front photo.

  Side view.

  Reflection port "A"  -25 dB. Note that 1296 MHz is not in center. I am using HP 8444A Tracking gen. and HP8554B specified for up to 1000MHz only. Reference is the red line. Hor. 20 MHz/div, vert. 10dB/div. The directionel coupler (for measuring "SWR") is HP97300B 1-20 GHz.

And port "B" -24 dB.

This is the coupling between port "A" and "B" - 19 dB.

  I did measure the "opposite" attenuation by using two helix antennas

 wounded in different ways.

  This is the reference, the right (wound) helix was used.  

  This is port "A" ("B" terminated) to opposite wounded helix.Apr. -25dB.

  And this is port "B" ("A" terminated) and next opposite wounded helix.

  And for rain protection put on some folio.

Some measure here: The monopole; length 39 mm, 3mm thick. The top cap 10-11 mm (has to be tuned).

Distance to back plate 55-60 mm (has to be tuned).

Diameter 170 mm and length 600 mm (limited by the material).

The septum wall is a scaled VE4MA 4 step.

Weight 750 gr (0.75 kg)

This special feed is going to be tested at SM0FOB this summer.  http://web.telia.com/~u85003229/

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Spectra. Hor. 100MHz / div. and vert. 10 dB / div. Max sigs  ~ -40dBm in to TS-2000 . At least something good with bad QTH -- hi

Hard life for an EME:er - this is the main swtich for 230 v AC.   It should stand 40 A !? Heeelp what did I do ...  hi.

ATF54135 , very small !

   SM5LE shack. To the left IFR signal gen. locked to rubidium. In center (the rack) from bottom: Power supply for PA. Sequencer, including switching 230v AC to switched PA power supply. On top PC/Laptop with GM4JJJ software and controller to SPID rotator. To the right TS-2000 included 1296 MHz module.

Curiosa: The TX/RX switching current out from TS-2000 is 10mA and to turn on and off the PA power supply is 4A that is "52 dB gain”! Hi.

Tripod with frame made of  TV mast tubes. The round plate is for the parabol mounting. Alfa SPID rotator with elevation.

Simple LNA with "hair-pin" input coil.   NF ~0.4dB (reading on a NF-meter). Gigatrim capacitors on input.

Going from 20x20 mm mesh to mosquito mesh does +1.2 dB in theory. The mosquito mesh is fitted outside the 20x20mm mesh with glue-pistol and adjusted with a mould to get the right shape.

SM5LE QSL card. Note the nice cap !

Do not trust PC's , rotator interface's and software's - please put in a mechanical end stop , a micro switch or something.

Do not trust PC's , rotator interface's and software's  - I use a baby sitter camera in front of a mechanical scale and a monitor indoors so I can calibrate the tracking. This equipment is not running when listening for the moon. "Absolute encoder" , one (1) degree is 5 mm on the screen !

PA made of 6 surplus 900 MHz cellular phone base station modules        The PA has 3 blowers for component side and 6  for the cooler.

availably from different companies.

The power dividers and combiners made of Sage Wireline and Wire Pack. A sort of semirigids with 2 innerconductors.   

Data: Pin 6W , Put 350 W , 45 A @ 32 V.                                                                                       

Using plumbers Teflon tape for isolation on 1296, makes the right cable "speed”, not air but Teflon.

Make your own 30 dB coupler from a semirigid or tefloncoax.  1. Cut isolation away.   2. Tin.    3. Saw up the braid  ~2cm (for 30 dB @ 1296 MHz).   4. Clean.   5. Make that procedure for two cables.   6. Solder together the openings toward each other.   7. Measure.  Should be refl. coeff. 25 dB and ins. loss "zero".

I did try to tune the phase to get max output ... hi !

How close shall I put the blowers to the cooler ? I did measure the DC out from a small blower placed to "air output" and pulled the 6 blowers forth and back to optimum DC and find that 0.5 to 1 cm was best.

Parabol was "meshed" indoors.                A mould to "tune" the mesh.                                   The chicking mesh was very stiff.

    The mesh was bended to get the right shape.

Completed dish .  2.2 meter diameter.     F/D = 0.34                     And an opening to get it out trough the door !

Make a ”Latching Transfer Switch” to a "PTT Switch" without logic or other active element. Needed: One extra 24 volt  relay one electrolyte capacitor, resistors and one diode.

28 volt on (RX mode) = pos2 (28v to pin 1).

28v off = pos1 (TX mode).

When the 28v goes off, there is a pulse putting the “latching coax switch” in pos.1. The switch will stay in TX mode (pos1) when all DC is off.

This schematic is OK for other ”Latching Transfer Switches” but depending on coil current might other capacitor value needed.

And here an Excel sheet for making a dish  (sorry , in Swedish).

Values for : 2.1m  - 2.2m - 2.3m - 2.4m - 2.5m  :   dish.xls

You can put in your own diameters and F/D.