5.7 GHz poor guy transverter

Not so many simple transverters for 6cm band seen up to now. So here is one, really simple and working, with minimum parts required and poor guy like me did find all the parts within the pile of microwave "LEGO bricks".

The architecture is traditional and straightforward, no bells and whistles in this design. The core of the transverter is the mixer. Simple as it can be, SKY-60 double balanced mixer working up to 6GHz with affordable price, new through the e-bay purchase. Drive on the IF port 0dBm @ 432MHz, +7dBm @ 5328MHz for the LO port. On the output RF port we have LO, LO+432MHz and LO-432MHz signal present. To get rid of the unwanted signals the mixer is followed by the filter. Here we can use many types of filters but the pipe cap was a simple and cheap solution, can be tuned easily even with no special measuring equipment. Tune to peak method will give good results. Of course the frequency is 5760MHz. This filter will be used both , for RX and TX operation. PIN diodes, RF switch, relay, resistor splitter or Wilkinson divider. Well, the Wilkinson divider was appropriate and simple enough for this approach. More over, no switching required for RX/TX operation. I made mine from the old 1.8GHz cellular equipment easily cutting out the peace of the PCB with the printed divider. Simple calculation, sharp x-act knife and the divider legs were modified to L/4 @ 5.760MHz. This way I end up with two ports, one for the RX and the other for the TX side of the transverter. For the RX front end i choose not the best, but cheap and simple MMIC block with the MGA-86563 declared to work up to 6GHz with not so bad performance. The MMIC was biased for the maximum gain with 8V power supply. On the transmitting side there is also a MMIC block, simple Sirenza SNA-586 good up to 6GHz biased for the maximum gain with 8V power supply. 

So this is it, a simple transverter, of course with the limited performance but good for the quick qso with the neighbor station or somebody on the hill within the line of sight. To operate this transverter we need some kind of local oscillator and a simple electronics handling the power and antenna switching. Crystal oscillator with the chain of multipliers can give us maybe better phase noise but better stability and more flexibility in choosing the IF insure the synthesizer built fir microwave frequencies. I choose the VK3XDK Si-4133 synthesizer version with the 16 programmable frequencies. The synthesizer is locked to high quality 10MHz double oven oscillator granting excellent stability and lower phase noise comparing to the cheap 10MHz canned oscillators. I prefer to use the 70cm IF so the LO was programmed to 1776MHz. The 13dBm output was attenuated with the 7db attenuator to safely drive the 3x multiplier box producing some 15dBm of the signal @ 5328MHz. Again 7db attenuator between the multiplier and mixer to bring the signal to the required mixer level. At the same time the mixer was very happy to "see" the 50 ohms impedance at any port. For this experiment i choose the IF 432MHz, but much better will be 434 or higher. Not more than 0dBm is required on the mixer IF port, so the 27dBm (500mW) signal from the FT-817d was reduced with the 26db attenuator at the sequencer board. Sequencer is also switching the power for the MMICs in the transverter as well as the power for the coaxial relay at the output. RF sensing and PTT ports insuring high protection. If the coaxial relay or RF electronic switch is not available we can use two separate antennas for the RX and TX. With this arrangement the setup is ready for the smoke test and initial qso testing. The output power is low, not reaching not even 1mW and the conversion gain is also poor just a few db so some extra amplification is required for serious work. 

Good LNA will lower the noise figure and improve the conversion gain and on the other side a few MMICs on the TX side will give us pleasure to work some distant stations. Just for the test I add another SNA-586 on the TX side bringing the signal up to the 3dBm. Not much, but at the same time I add another pipe cap filter between the MMIC blocks to reach the cleaner signal at the output. Result can be seen at the video. The same approach can be used to build the transverter for the other microwave bands, so no excuse for the low activity at the microwave bands. 

So "Use them or lose them"

24 GHz transverter update

As I received a few queries regarding the transverter here is the update on done so far. I make some small modifications but nothing that is diverting from the original idea. I did have a big problems with the YIG PLL oscillator MTS1500 which was not working properly. I discovered that the YIG inside the whole unit is faulty, can not be locked neither controlled properly. After so many time devoted to this unit I quit and order the other YIG PLL oscillator DFS-1201 which is working as required, immediately after first start. More over I program two frequencies so the same unit can be used aloso as the LO for the 47GHz operation.

Briefly, here we have a DFS-1201 YIG PLL programmed for L.O./2 frequency to suit the 436MHz IF. DFS-1201 is controlled via the small PCB with the PIC microcontroler (directly on the DFS-1201 connector) where 2 programmed frequencies are available. The output signal is 14dBm and splited in two for upconverter and downconverter. No waveguide relay as mentioned previously, isolator is good enough to protect the downconverter from the 300mW which can produce the TRW upconverter.

The bottom PCB is switching the voltages for the units and acting as a small sequencer together with the IF attenuator and switching.

Power supply boards with the voltage stabilisers are attached to the left/right walls of the plastic housing.

The antenna is attached directly to the third isolator port through the short peace of the WR-42 flexible waveguide. The antenna is not so big and the radom has been dismantled to make this system light and easy for operating. Even not so big the antenna is quite sharp and careful pointing is required.

Some initial test were performed and overall feeling is that the transverter perform very good. The RX NF is very good and the YIG PLL stability after initial warming up of 5 minutes is excellent. Circulator instead of  relay seems to be a very handy because no headache and fear to burn the downconverter front end. No "smart" sequencing is required and loss are reduced to the minimum.

Present ODX is 168.5 km LOS qso during the summer with the humidity close to 90% over the sea path. Winter should be the right time to gain this distance.

73 and CU on 24GHz

W1GHZ cheap 3cm beacon board

Some time ago besides some other PCB's I ordered also the board for the simple 3cm beacon oscillator project from Paul, W1GHZ. The price was really affordable, and you never know when you will need some simple multiplier project like this. The latest, I heard that he is running with stock low of this board, so this means that people are building this stuff more and more. On the other side, not so many feedback on the web regarding the results obtained from this simple multiplier leaving idea that all this projects are working perfect with no problems or they are not working at all and people are giving up without an extra effort to tune properly this interesting approach to old fashioned multiplier idea.

So here it is, completed and tuned multiplier for 10368MHz. Of course, I did make some small modifications to get the best results from this board, at the end it is working. I saw that Paul published the update on this project, but maybe somebody will find my hints useful too. 

The first thing that can be noticed, my tuning screws are quite long, this is not necessary. I did use the same project for some other final frequencies (11808MHz) and I left the screws long enough also for the lower frequencies. The size of the screws: M4 brass for the first (3.5GHz) pipe cap and M3 brass for the other two (10GHz) pipe caps.

Secondly, I did use 9V power supply, instead of 8V. The only reason was the 9V voltage regulator that was handy for me. All MMIC bias resistors are modified to get the best results with 9V.  As there is enough place on the board, I have two resistors in series for each MMIC stage. This way I can easily tune the bias current and the dissipation on resistor is lower, even I am using 1208 SMD bias resistors.

About MMICs, I mount 3x SNA-286 and 2x NLB-310. I went through the data sheets quickly, and I noticed that ERA-1 is quite poor for the 10GHz and decide to use NLB-310. I don't know how Paul manage to get the 11dBm from ERA-1 on 10GHz, but this is not option not even in the data sheet :-)

So, this are all mods. done from my side regarding the original approach. Let's start with tuning...

I have to said that without Spectrum analyzer not reading the Paul's advice, tuning this multiplier can be quite confusing. So, at least any kind of power detector able to detect -10dBm @ 10GHz is a "must" to reach the final result. For the signal generator, I did use the handy Si-4133 generator where i have programmed 16 well known microwave frequencies. 1152MHz and 5dBm is what we need. 

The first pipe cap should be tuned  to x3 = 3456MHz. This should not be a big problem because of the size of the pipe cap that does not allow to tune to the 2nd harmonic frequency. With the screw completely inside, backing the screw a few turns out the strong signal / power peak will be present at certain point at the first SMA tuning point. At this point you are at 3456MHz, all what we need from the first two MMICs and big pipe cap. Backing the screw more out you will reach another peak of the signal, almost the same strength, this is x4 = 4608MHz. If you have a sensitive power meter or detector, backing the screw almost completely out of the pipe cap you can observe some weak peak also on the x5 = 5760MHz frequency. So, this pipe cap can be tuned to 3 different frequencies, our goal is to tune to the lower (first) one.

This step was quite easy, the next one will require more precision and patience. The two 1/2 pipe caps should be tuned to 10368MHz. They are to small to be tuned to the x2 =6912MHz and they are too big to be tuned to x4 = 13824MHz so the only possibility is to tune them to x3 = 10368MHz. With the M3 screws completely inside slowly backing them, some where in the middle of the pipe cap you will notice the power peak at the output SMA. You will need to tune both pipe caps parallel to reach this point. Once you reach the peak, tune the both screws for the maximum output signal. This should bring you on the 10368MHz.

Looking nice, well more about this later :-)

Following this procedure the power I get on the 10GHz was only 0dBm, not even. The first thought was, where the f... I lost the 10dBm?? Driving the multiplier with the different power levels I found the +7dBm  @ 1152MHz gave the best output (+1dBm). But this is still far away from +11dBm...

I start to play with the first MMIC (SNA-286) bias resistors, and there was a nice improvement. I had to increase the resistor almost double to squeeze the maximum from this first multiplier stage. The output power went easily to +5dBm. I thought that same procedure with tuning the third SNA-286 bias multiplier will bring up the output power to desired +10dBm but this was not the case. Changing the bias did not bring any better results. Maybe SNA-286 are not so good in producing the harmonics at higher frequencies??

So, for the moment I stopped here, +5dBm @ 10368MHz is good enough for me, but for sure I will investigate the difference between the ERA-2, SNA-286 and some other MMIC candidates in producing high reach harmonics above 10GHz.

Let's go back to a nice looking signal shape from the picture before. Really nice ha? OK, there is another (fuzzy) shot of the Spectrum analyzer screen.

Not so perfect, ha? Well, believe it or not, this is the same signal from the previous picture. So where is the catch? To simply explain, I will compare this with the Miss universe competition :-) Looking from the balcony all those girls looking nice, but coming closer we can see that some of them are looking not so good as from the balcony. Same here, if you use the span of 100MHz you will get the first picture, if you use the span on the S.A. of 1MHz you can  get the 2nd, more realistic picture.

Well, this have nothing to do with the multiplier, but just want to give you an idea how Si-4133 signal looks after x9 multiplication. I want to gain that my Si-4133 oscillator is using the good quality Isotemp double oven 10MHz reference oscillator, so imagine how the signal will look using the cheap 10MHz canned oscillator.

I get the nice phase noise comparison measurement chart made recently on the MUD 2012 meeting compiled from Paul, W1GHZ. So all credits goes to him and the guy who measure it. Nothing more to add...

At the end, just a few ideas where to use this multiplier, of course the first idea will be a simple 3cm signal beacon source. I did use the same to generate the 11808MHz signal for one of my 24GHz transverters. You can hook up also the Comtech ATV TX tuned to 1161 MHz to reach 10450MHz. Driving this multiplier with the 720MHz can result with the output of 10800MHz which can be a simple L.O. solution for the 10368MHz transverter with the I.F. 432MHz (LSB). So many solutions for the simple multiplier.

By the way, if you manage to reach +11dBm of output power, let me know...

Simple 6cm - 5760 MHz beacon

This is just another simple beacon for 6cm band that came out as a result of raining afternoon and a desk full of various microwave components. Of course, this can be done on many different ways but I choose to use the parts that are cheap and available to every microwave builder. As most of my designs this project is also modular where every component can be replaced with some other, resulting maybe better, maybe worst performance but at the end the output signal level will be within the range of a few dB of difference.

This is a block diagram of the beacon oscillator from my scrapbook. After so many simple project I start to take a notes with at least few measurements so If I need these data later, they are always here in the notebook. Th PC is nice but notebook is better.

So no detail electrical diagram this time because all blocks are explained already through my previous designs. The beacon is built around well known S53MV crystal oscillator used in his beacons or ZIF microwave radios. The 720MHz signal is attenuated to a level of approx. 5dBm to drive more efficiently the 6cm multiplier explained on my blog. As we are dealing with the multiplying factor  of 8, not much of the signal is left at the required frequency of 5760 MHz. This signal is amplified with a two MMICs blocks, the first one withe the NLB-310 and the second one with the SNA-586. The output power is around 10dBm or 10mW. The filter is optional, but recommended, reducing the output power to 8dbm+

Going from the left, the 720MHz oscillator (still not screened) is starting with the 20MHz crystal. This is a common value where also cheap computer grade crystals can work. There is a tuning inductor and trimmer capacitor with possibility to tune desired frequency, in my case at the beginning of the band, but leaving enough room for EME operators. after the multiplying chain (x3 x3 x2 x2) we end up with decent level of 11dbm+ for the next stage.

Maximum allowed input level for the multiplier is +10dbm, so attenuator was required in between. Playing with the attenuator values I found that the 6db attenuator will give the best results, higher output of the multiplier for the 8x multiplying factor.

The multiplier was driven with the 5dBm of the signal for the best performance. Even better results are possible by changing the value of the bias resistor in the first MMIC multiplier stage. Usually higher resistor value will give up to 3dB better output signal for desired input frequency. I did not play with that in this project, so there is room for improvement. I got -9dBm of signal after the multiplier.

MMIC blocks are simple and cheap and they have a decent gain. I choose the two different MMICs to see how they perform at 6GHz. The first one with NLB-310 is working very nice with the 11dB of the gain producing almost +2dBm of the signal. The second one, SNA-586 gives another push to +10dBm with the gain of just litle bite more than 8dB on 6 GHz.

The filter is optional but can be very useful if you plan to use this beacon on remote high location. 3/4 pipe cap filter can be the easiest solution. Just tune the filter to maximum signal and this is enough. Place the filter between the MMICs to isolate them with the I.L. of the filter. After initial attempt my pipe cap filter was inserting 4dB of loss, a bit high. Then after fine tuning I was able to reduce the I.L. to only 1.6dB @ 5760MHz. Inserting the filter the output drops to +8dBm.

The last component (gray)that can be seen is directional coupler. This is not a part of the beacon oscillator. It was used just to simultaneously monitor the signal on the frequency  counter and the spectrum analyzer.

This is the core of the 6cm beacon. The rest of the parts that are required are beacon keyer, power supply and the antenna. The keyer is already explained on the blog, where multiplier stage should be keyed with the positive voltage. Power supply can be anything that can give you 500mA @ 13,6V. The antenna type depend on the requirement, simple horn or slotted waveguide can be a solution or if you want to go really cheap and simple, a simple vertical Wi-Fi 5.7GHz band can be good also but vertical polarization will produce less signal for H-pol weak signal users. For a home use, this is the best-buy option.

Modification TOKO 5HW-1150-45F filter for 23cm band

I have this nice and small (and expensive) helical filter in my drawer for some time. Looking the TOKO filter data-sheet this is very nice filter for the 1152 MHz local oscillator project, but I want to use the same one in my 23cm transverter, for filtering 1296 MHz. The data-sheet states that it is not possible to tune to the desired frequency. Of course, there is another filter covering that particular part of the band but my drawer is not TOKO store :-)

 Going back to the data-sheet... It is clear that this is double tuned helix type filter, center frequency 1195 MHz with the coupling done through the window inside the metal shield. The connection diagram (F connections) in the data-sheet does not give a real situation of the helix inside the shield. From the diagram we can see that there is a helix between the hot end and the ground connection and a small part of the helix continuing after the hot end pin connection. Basically, the idea is just to short the helix to bring the resonance higher using cut and try method, but following the diagram there is nothing much to cut on F version.

On the other side I got the hint from Goran AD6IW that he make the mods. on the same filter very easy and simple and this should work, so this was good reason to try and see what is going on inside the "mystery helix".

Do not be afraid, this is going to be very quick and simple modification. You do not need not even a soldering iron, just a small sharp cutter and a small flat screwdriver. Each of the helix is secured inside the housing with the 4 dents, 2 on each side. Using a tip of a sharp flat screwdriver bent vertically all 4 dents to free the brown helix former. Pull out the the  helix former, and you will have the same situation as from the following photo:

You probably ask yourself the same question I ask myself too, WTF is worth 20$ inside this helix filter ?! Do not look and search for any other parts inside the metal shield, there is nothing else inside except the tuning screw :-)

First thing that you may notice is that the real situation is not the same as on the diagram. The "helix coil" between the hot end and the ground pin is just a bridge from one pin to another, no any helix turns at all, as showed on the diagram. The helix is then extending from the live end pin around the coil former exactly 5 turns. What we need to do is just short the helix to bring the center resonance around the 1296 MHz. Cut and try method was the simplest one and gave excellent result. The helix is soldered on one end to the connecting pin and the other free end is just bended wire inside the gap of the coil former. To bring the resonance up, simply cut and remove just 1/4 of the last wire turn from the helix using the tip of the sharp cutter. The wire is stiff enough to stay on the coil former, but if you feel that the helix will be unwound secure the helix with the drop of super glue. I did not use this method because I didn't know what effect can cause the glue to the coil resonance and Q factor (if any?).

Use the same procedure for the other helix in the filter. After all, insert the coil formers back to the shield and secure them with the same 4 dents from the beginning of the modification.

So that's it, just a 1/4 turn shorter helix solved the problem and the filter is tuning smoothly to the 1296 MHz with almost identical response curve. I did check the filter directly soldering the SMA connector to the live pin and ground shorting the ground pin and shield. This was much simpler than soldering the filter on the special PCB. The proper way of tuning will be using the network analyzer but this is not so common among the HAM experimenters so simple generator, oscillator on 1296 MHz and LNB diode detector can do the job also.

Finally, check this cheap and dirty approach, the LNB IF MMICs (C1H & C1E) board with the modified TOKO filter. -13dB of input gives out filtered +12dB of signal on 1296 MHz. You can use this board both way, for RX & TX, so simple, the half of the 23cm transverter is already here :-)

5.7 GHz with Microwave LEGO bricks

Microwave lego bricks for 5.7 Ghz

Just downconverter part:

L.O. = Si4133 pll Fout=1776 MHz  (10Mhz reference triple oven)
Multiplier x3 = SNA386 + SNA586
I.F. = 432 MHz

1st brick = MGA86576
2nd brick = Pipe Cap filter 5.7 Ghz
3rd brick = MGA86563
4th brick= Mixer SKY-60LH

Simple LNB diode marker (harmonic multiplier)

Based on G3PHO marker generator.

Double LNB mixer diode can be used as well, but only one diode from the pair. Leave the third pin NC in the air.

Tested up to 24GHz, check the video, 1152MHz / 13dBm input = 10368MHz out

And the second one, 1336MHz / 13dBm input = 24048 MHz out (18th harmonic!!!)

If more signal required or wider range, place the diode across the Vivaldi type UWB antenna....