Tuesday, October 28, 2014

Playing with the ELCOM Ceragon DFS-1201



The easiest way to get a descent local oscillator for the microwave bands is purchasing the synthesizer fabricated by the Elcom technologies Inc. Most of mine units are purchased through the E-bay from well know Israeli vendor. To be honest, I was not so lucky with that as most of the units are not working or not working properly. It is well written that the vendor does not guaranty that the units are working properly, so it is on us to decide to buy or to skip... From time to time there are some new units available, sealed, followed with the documentation. This is the way to go. True, the price is almost double but buying four units and having one descent is even more expensive :-)


Let say you get lucky and you have your unit in order, you will need the controller to run this brick. Most of the guys are using Dave - WW2R design. What yo need to know is that you have to multiply the required output synthesizer frequency by 3 and edit the ASM code just using the first 4 digits, compile the HEX and program the PIC 12F675. Plug the power and the lock LED should blink once and lighted. BINGO.
This happens if all is going by the book.

The first sign that something is going wrong may be a LED not locking the ON state. The first thing is to check if the math was ok. Let say you want to program the 11800 MHz frequency. 11800 x 3 = 35400
So you need to program the ASM two lines with the 3540. Of course, the Dave HW is supporting two frequencies, so program another convenient one.
Still not working?
Well, do not expect to have the units working out of the indicated range. Many guys are looking to have the DFS-1201 running on 12.023.333 MHz (for the 24GHz beacon) but mine experience is that the units can lock from 11.250-11.860 MHz, so even narrower than declared.

Surgery - getting a screwdriver (better a battery one :-)
You can always open the brick. If you are lazy to unscrew all those screws, check the picture:


Simple as beans soup :-) The VCO is running on 2.8-3.0 GHz. There is a buffer right after followed by the resistor splitter for the PLL and MMIC doubler 5.6-6 GHz. There is a high pass filter and another 6Ghz MMIC amplifier to provide enough power to drive the x2 multiplier diode. A long 12GHz filter then is followed by 2 stage FET amplifier. The total multiplication factor is 4. Clear ?

Guys owing the Alcatel White box 23GHz equipment needs the oscillator running on 5.9GHz. This is not so common surplus e-bay unit. DFS-1201 can do that ! All you need to do is to run the 6GHz signal from the amplifier just before the diode doubler to the output SMA connector with a peace of semirigid coax placed where the diode multiplier, 12GHz filter and 2 stage amplifier sits. All this multipliers and amplifiers (except tha last 12Ghz stage) are Sirenza S1 and S2 (ERA-1 and ERA-2 mmics) so you will have more than enough power for your White box 24Ghz transverter.


I did not play around the PLL side so much, but briefly, the reference oscillator is running on 100 MHz and heated as per above picture. The signal is then multiplied by x9 and filtered with two ceramic filters. Another mmic multiplier by x3 using INA10386 mmic followed by 2.7Ghz hairpin filter. This signal is then going to the mixer on one side and the signal from the VCO from the other side and we have the mixer output of 100-300 Mhz going to the lowpass filter and then after to the PLL. The complete picture of the digital part is here.



Most common problem is that the frequency is odd. Of course, aging of the crystal with the constant temperature is resulting to have the output frequency shifted (in my case 23khz @ 12Ghz). Just above the crystal there is a small part looking as the trimmer capacitor, so this may be re-tuned, I think so.

I had some other problem, when cold, the unit lock properly, but after some time when heated, if the unit is switched on/off I can not get the lock state and no output at all. This remain to be investigated.

On some DFS-1301 unit I can not get the lock state at all, even when cold. Checked the VCO control voltage from the charge pump and the 6V measured. It should be 5V. After playing around VCO transistor (marked 420) i manage to get the lock, VCO control voltage drop to 5V. After restarting the same problem.
This should be also investigated. And yes, to run the DFS-1301 from the Dave board, the output frequency should be multiplied by 2 or divided by 5. Funny math, you get the same first for digits :-) to program the ASM code.

So that's all for now, at least my DFS-1295 is working properly if nothing else :-)



22 comments:

  1. I also have a DFS1301 which does not lock. Did you find out the reason why yours didn't?

    73 Barry G8AGN

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  2. There is a mmic in the PLL part just after the lowpass filter going to the PLL chip. Found out, on several units that this mmic in unstable or not working. Replaced the same with the simple MAR-6 (different layout) together with the new bias resistor (do the math). After that the DFS unit lock perfectly.
    Let me know if you have the same problem.

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  3. Many thanks for the hints. I'll look into this.

    73

    Barry, G8AGN

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  4. Have only just started to look at my non locking DFS1301. There seems lots of signal from the VCO which reaches the mixer H285 but the signal from the reference oscillator seems very low. The S3 mmic which amplifies the reference signal after the 2.7GHz hairpin filter seems to have a gain of about 10dB. The data sheet gives a typical gain for this device (S3 = Sirenza SNA386) of about 20dB. The output from the H285 mixer is on the correct frequency but is very low. The charge pump voltage goes up to about 10.3V after switch on so the VCO goes to one end of the tuning range. Does this behaviour seem similar to that which you saw?

    73

    Barry, G8AGN

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  5. OOps! The S3 mmic is in the VCO chain, not the reference chain. This is OK as there is a big VCO signal reaching the mixer. So the question is whether the Ref signal at the mixer is lower than it should be?

    Barry

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  6. Barry, you probably know that the DFS-1301 needs x2 programming scheme, right?

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    Replies
    1. Yes, I know about the x2 as I already have another 1301 which works OK. I've just re-read your original posting about where the faulty mmic might be and will check the signal levels there.

      Barry

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    2. Well, I need to update the post. Meantime i found where is the problem and the part that should be replaced (modified). I found some odd behavior, the PLL does not lock when cold or the PLL does not lock when hot. I found the tre problematic is the small MMIC just after the low pass filter in the PLL chain. The mmic was not wirking properly and you can check that simply by measuring the bias voltage and current through the bias resistor. You can even try to heat the mmic with the hot air to observe the behavior. I remove that mmic and insert a simple MAR-6 with different bias resistor and the units start immediatelly. I experience that units where the lock is obtained much faster (lock state LED) are less problematic from the units where the LED blink is longer.

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  7. I've now got one of my faulty DFS1301 working by replacing the mmic which is just before the PLL chip, as you suggested. I used a Avago 52563 chip which is the same size as the original mmic and has 6 pins, 3 on each side so replacement is easy. I didn't change any resistor values.

    73 G8AGN

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    Replies
    1. That's nice. Not any DFS1201 or DFS1301 left on the e-bay. So what are your plans, 24GHz or 76GHz ?

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  8. I have working gear for 134GHz using a 1201 at 11.2GHz but will use two 1301 units for 76GHz (receive) and hopefully 241GHz(transceive using a 1301 at 13.39GHz. This is outside the official frequency range but one of my 1301 will do this). For Tx on 76 I plan to use a 1295.

    I also have some 1101 units which are faulty as the VCO is not working so will probably have to change the 420 (AT42086) transistor. The DFS1101 uses a 92.5MHz xtal. Some 1101 units are still available from Art in Part and do cover 11.2GHz.

    73 G8AGN

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  9. I have been told that the DFS1101 uses x2 programming but I haven't been able to check that yet.

    73 G8AGN

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  10. I found that one of my DFS1101 would lock up when no PIC was in the G4FRE programmer but wouldn't lock up when I put the PIC back in. I solved this by adding five extra commands "call delay1s" in the G4FRE code after the original ones.

    73 G8AGN

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  11. It lock probably in the center frequency range. This is already known. Introducing delay from your side is a smart idea. Have you check the actual output frequency?
    maybe the VCO is "lazy" and introducing extra delay helps.

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    Replies
    1. Without the PIC, the Elcom DFS1101 locks at the centre frequency of 11.0 GHz. With the extra delay, the Elcom locks at the correct frequency I programmed in which was 11.2GHz. I've checked the spectrum and it is very good.
      73
      G8AGN

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  12. Good to have some more info about DFS1101. I have seen some 50+ pcs left on ebay Izrael vendor stock.

    thanks
    Adam

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  13. I've been working on directly programming the PLL in the DFS1101,1201 and 1301. I've designed a programmer based on an Arduino Nano and it seems to work well. Details will be published soon in the UK Microwave Group's "Scatterpoint" newsletter.
    73
    Barry, G8AGN

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    Replies
    1. Barry that's nice. Accessing the PLL directly so you can program any frequency or still using the internal PIC and limitation 3.333MHz step ?

      Can you send me an email, have few more questions.. thanks..

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    2. I'm not using the internal PIC but taking wires directly from the 10 pin connector to the PLL chip. The Arduino Nano programmer plugs into the 10 pin connector instead of the G4FRE programmer and can store a list of many frequencies. These can be selected using a simple push button. The Nano LED flashes to tell you which frequency has been selected from the list. You are not limited to the original frequency steps.

      Barry

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    3. That is nice feature in deed. I think I fried one DFS1201 PLL trying to directly program the PLL through the pic 16f84. Did not work and I replace back the original PIC in DFS1201, but not working also. I found some surplus telecom boards using the same PLL so I may repair that PLL as there is no dfs1201 left on the market :-) Drop me email on adam9a4qv on yahoo mail

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  14. I now have a DFS1295 working in my 76GHz rig.Tx 75980, Rx 76410 (434 IF on low side). Best DX so far with G0EWN is 10km under very wet conditions so we should be able to work much further in good weather.
    The 1295 has not yet been modified for direct PLL programming but I will do so as then I can get frequencies like 75976 for Tx.
    73
    Barry G8AGN

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  15. Sorry, with 76410 the 434IF is on the high side - reverse Rx tuning. With a DFS1301 modified to program the PLL directly I can get 440 or 432 IF on the low side.
    73
    Barry G8AGN

    ReplyDelete