Synthesizer with ADF4351

I have discovered interesting synthesizer modules on eBay:

I have also found an interesting project from Alain, F1CJN on the Internet.

This synthesizer can easily be controlled by Arduino Uno and a Shield with LCD Display:

Final result is here. A synthesizer that can be programmed for many stored frequencies. Following picture shows one of them:

I will upload more about this wonderful synthesizer shortly. Hoping to use it for a small local beacon for 23cm.

73 Herbert

UPDATE 2016-06-07:

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Nothing is perfect. Not even synthesizers. There is a serious problem with spectrum purity when used for frequencies above ~ 1.1GHz. See following pictures.

We need 960MHz reference signal for a Microsource YIG that generates 23GHz. Spectrum around 960MHz seems to be OK:

However, 1296MHz seems to have a problem with spurious signal only 25MHz away and only 39dB suppressed:

Workable solution seems to be to generate the beacon signal on 1/2 frequency and double it. That would require 648MHz. Following picture shows reasonably clean spectrum for that. You can see the 2nd harmonic on the spectrum analyzer already:

Looks like I have to work on frequency locking in my lab - frequencies shown on my RIGOL analyzer are little off the frequencies shown on the Arduino. Luckily, this synthesizer allows (wonder of all wonders) locking to a 10MHz reference!

(to be continued)

73 Herbert

AF4JF

UPDATE 2016-06-10:

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I have retrieved my old 23cm filter that I built long time ago with the idea of using Flex 1500 with IF between 28 and 50MHz in mind. This filter was made per W6PQL description and is described incl. pictures and frequency response in my other posting here.

Wonder of all wonders, it fixed the problem! The 1296MHz signal is a little weaker (6-7dBm) but all unwanted peaks seem to be suppressed more than 55dB:

In fact, I can't identify them in the noise floor anymore. Definitely good enough for a small local beacon! I will follow that idea soon ...

73 Herbert
AF4JF

Another Synthesizer Issue

I have published my findings with a MICROSOURCE synthesizer here some time ago. That synthesizer is working fine, along with several  other ELCOM LCDFSL-1201 units in my shack. I thought that ELCOM interface is pretty transparent - until I decided to use LCDFSL-1101 programmed for 10.8GHz (10.368 + 432 = 10.8). Well, it isn't.

I have browsed Internet for a while and discovered that many others would like to know how to program that unit. There even is a new controller board for it on a web site in Australia. Hmm .. maybe later, perhaps in winter time. For now, I have found easier solution. Use ELCOM DFS-1101 instead.

The DFS-1101 does not have connector for external reference. There is an internal Xtal used (I believe 100MHz) instead. This unit uses funny frequency calculation: you have to divide the wanted frequency by 5 and add 1024 to the result. In my case (need 10.800GHz):

10 800 / 5 = 2160

2160 + 1024 =  3184 ..... 31 84 00 is the code the interface needs to generate 10.800GHz

I will keep looking for a solution compatible with my LCDFSL-1101 unit. Until found, this cheap DFS-1101 will do the job.

 DFS-1101 unit (left) with my test board with PIC (WW2R design)

Frequency ~ 10.800GHz, voltage 14.7V (before stabilizers), current 646mA.

Unit works with +6V (some ELCOMs require 8V)

MICROSOURCE Synthesizer Issue

I have obtained two MICROSOURCE synthesizers some time ago. Label on that device says:

       FREQ:   10.2 - 13.35 GHz

I was told by several other HAMs that this unit is practically identical to ELCOM unit and can be controlled through a device with 12F675 processor, such as described by Dave WW2R here. The only difference is supposed to be the oscillator type - ELCOM uses "DRO" while MICROSOURCE uses "YIG".

I am not a beginner with ELCOM synthesizers. In fact, I already have a 24GHz transverter based on DFS1201, so I thought that using this new MICROSOURCE unit to generate signal for 24GHz beacon would be piece of cake. Well ...

The synthesizer simply refused to cooperate. I tried to program it for various frequencies above 12GHz, but it always generated 12GHz output signal (note that my counter isn't locked to GPS yet):

I spent hours researching Internet and checking my wiring, switching synthesizers .. nothing. I even contacted Dave WW2R by email, but he didn't have "hands-on" experience with this model. After quite some time I finally remembered that Michal OK1VM published something about this synthesizer on his web site, so I have sent him an email.

OK1VM told me that he has some recent experience with this synthesizer. He also mentioned that although the label on the MICROSOURCE unit says otherwise, it ONLY responds to programmed frequencies in the 11.2 - 12.0 GHz range. So, I have modified my programming to 11.88GHz and here was the result:

OK, the synthesizer works. I can't use it for a small 24GHz beacon, but there are many other ways how to utilize these wonderful devices. 

Again, no matter what the label says, both of my MICROCOM units let me set them to a frequency in the 11.2 - 12.0 GHz range ONLY, exactly as DFS1201 from ELCOM.

So, before you decide to buy such a unit (mine came from eBay), be aware that your synthesizer might have the same limitation as mine does.

Thanks to Dave WW2R and Michal OK1VM for their help with solving this mystery!

73 Herbert

Even more 24GHz Toys

Thanks to recommendations from  Eda, OK1EM, I have obtained some more microwave modules useful for building 24GHz trasverter for ham radio use. These modules are called "DMC" and I have bought them on eBay:

This is a TX-mixer combined with an amplifier. It works well with IF on 432MHz, but requires local oscillator around 23.76GHz about 8dBm. Output on 24192MHz is between 20-40mW. Note that you have to use a filter between the mixer and the amplifier. This module conveniently provides SMA-connection points for such a filter.

This is a RX-mixer. Disregard the 1510MHz label, it works with 432MHz too. We only use the input section that ends with "1510MHz Output", the other section converts the signal to 70MHz and we don't need that, so disregard the cable jumper on 1510MHz.

This is an oscillator. It is based on a DRO element on 1/2 frequency (around 11.8GHz) and a crystal around 104MHz, depends on a model and on output frequency.


DMC modules are more common in EU. Following links show some basic info from web sites of  two HAMs in the Czech Republic. Links open in new window:

OK1EM  and  OK1VM

Please pay attention to block diagrams here and here. Nice and very explaining picture also here.

I have also gotten a nice dish antenna right for 24GHz, made by MACOM. It even comes with a radome.

Open antenna with a feed

This shows the entire assembly

One more 23GHz antenna assembly from eBay - I am going to use this with my "small test station" (described here). This little antenna has a circular waveguide feed.

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Following device is not directly related to 24GHz, but it will be used to adjust oscillators for all microwave bands. Following picture demonstrates a temperature regulator (works with a temperature sensor and a relay that controls power for a heater plate):