Posts by PA3FYM

    Good, I'll try to dive into the matter in order to solve your airconditioning issue ; -)

    It now polls the status during mod TC, that has to be speeded up.

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    Oh, you mean an even smaller balloon? I haven't even considered that. My guess is that it would be below the measurement noise then, but I'll have a look tomorrow.

    Yes, these 'large spirals' are not uncommon, but at marker 1 there is a discontinuity which I suspect will be the 'circular polarization' balloon.

    How about marker 1? I think there is your balloon in the vincinity of Z = 1 (normalized) of the Smith Chart. Perhaps you can reduce your span to zoom in?


    Then . . . I can('t!) repeat this infinitely ... don't stare yourself blind at these measurements and resulting pictures. A few decades ago (when sex was dirty and the environment clean) having a RL of 10 dB (equals VSWR50 = 2) on the microwave bands was considered 'enough', anything more was 'nice to have'. People having worse RL's are still alive (and making contacts over QO-100)


    The 'loss' (with RL = 10 dB) is only 10% of the power, so the remaining power is 90% which, relative to RL = ∞, is 0.46 dB less (!)


    Also, related to the difference between linear and circular polarization (theoretically 3 dB), mutilation of the axial ratio will be a fraction of that.


    "Deutsche Gruendlichkeit" is not always 'the' solution for a problem ;; -)

    DH2VA Agreed, but I am 'in the flow' or focusing on this parameter only for practical purposes. Fast lock, stability & accuracy (and cheap! : -)


    Concerning Saw Tooth Correction, had lots of experience with that while running Stratum 1 ntp-servers, but to go that far ... We only need 1E-10 precision/stability ; -)


    Variance / jitter on the PPS (which is an intrinsic issue with GPS ; -) is attempted to deal with by Lars, have to dig into that issue too. Now there is a low pass filter trying to smear out/average this jitter. The system is not punished hard when it misses a PPS.

    SV1BDS I saw the data, interesting ... (first read the mail, didn't understand, until you now tell me you switched on the air conditioning, haha : -)


    What happens is that the DEMA, the statistical (or some say economical parameter, especially when it's used in stock trading algorithms) parameter to control TC is floating around zero (0) when TC reaches a certain value, in your case 770 seconds.


    Because the DEMA didn't exceed max deviation (arbitrary value, chosen by me as intuitive/educated guess) -at the moment when the decision has to be made to increase the TC- the contraption gets rewarded with a longer TC, in your case:


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    1. TC += TC>>4 = TC + (TC>>4) = 770 + 48 = 818

    (B.t.w., 770- 818 seconds is a good value, which means 'the flywheel' is running stable)


    'Normally', when DEMA drifts away (at least that is MY philosophy/addition/interpretation) in such a matter that it's risking 'flying out of the bend' this is a sign that the contraption cannot remain its lock with the current Time Constant. So, before it looses lock, the TC is lowered until it reaches a moment that the system remains in lock and that the DEMA is in control and you get 'through the bend' with your car ; -)


    However, when a 'severe' discontinuity during this process (i.e. while almost flying out of the bend with your car) is involved and you try to press the brakes, but somebody cut the brake hoses (in this case switched on the airco ; -), a crash (or loss of lock) will be inevitable. That is what happened here.


    Hmm.. let me think about it (was some time ago I designed this addition), nice mental puzzle ...


    Of course, the external (exterior of the OCXO etc) are of importance. When your contraption is not inside a case, the impact of the airconditioner will be larger than when it's inside a case.


    A quick and dirty remedy/experiment could be adding Temp-compensation (NTC or LM35 at (iirc) ADC2) and see how it behaves. Anyway, my recommendation is to box your contraption first.

    I have to work now on clearing the output signal from harmonics etc. The OCXO alone is clean but when others units powered is become dirty.

    Yep, known issue ; -) That's why I always emphasize denoising power supplies when using this kind of applications (accuracy & stability), but apparently you have to experience it to place my comments into perspective ; -)


    In the end noise (reduction) influences the time constant (TC). I regularly see a TC > 500, so that must be possible for you too.


    Some other tips/hints I did:
    I placed a temp sensor (LM35) on (I think ADC2). When you don't use temp compensation, ground that ADC pin , otherwise it is left open and produces noise.

    It is not by coincidence that open ADC inputs are used to produce cryptographic keys ; -) Same accounts for the other T-sense ADC pin.


    I placed a 100 uF cap between Vref and GND on the Nano board (on the board is 100n, but I increased that ; -)

    SV1BDS Promising video ! : -)

    It is now interesting to which your TC converges. I placed a 10 uF cap between the RESET-pin and GND to prevent rebooting the Nano when connecting a RS-232 terminal (e.g. Putty) (cap has to be removed when reprogramming the Nano)


    Here the TC 'wobbles' a little due to the statistics I apply on diff_ns as an attempt to 'restrain' the contraption, so that it can't drift away, read: prevent loosing lock

    DB2OS Thanks for the posting/link. From the information I (me, myself and I) have the Dutch administration (so the 'boss' of the German BNetzA) doesn't oppose to the French proposal .... Unfortunately the only person with in depth technical knowledge of radio (frequencies) at the policy department (Ministry, The Hague <-- they decide, not our BNetzA) passed away recently , so our lobby was/is unfortunately 'de facto' unsuccessful . . .

    The question remains if the amateur service (not having a formal vote in the ITU/WRC in the end ... ) is able to convince others / administrations to 'reconsider this proposal'.

    DD4YR It has all to do with linearity, so that 'in channel intermodulation' (free translation from Dutch) doesn't smear out (to other channels).


    Just like the old analogue CATV systems, which used e.g. BFW16's or other 'power' transistors in their distribution amplifiers. In my (illegal) FM transmitters at that time (80's) these BFW16's were able to produce almost 1 Watt, but for linear purposes there needs to be an OPBO (Output Power BackOff) of ... say .. 10 dB (or more depending on the application).

    To clarify, this thread is not intended to 'poke' but merely to document the development of new phrases/sentences which seem to develop as a kind of 'QO-100 language'.


    G8UGD In most cases the sentence concerning SDR Console is followed by "locked on the PSK-beacon" ; -)