Posts by PA3FYM

  • MY QO100 SETUP

    I am a member of that forum and posted some in this specific thread. I first want to fiddle with it some more before I release the code. The Lars GPSDO is now a dedicated QO-100 reference and I moved my other reference back into the shack to feed the measuring equipment : -)

  • MY QO100 SETUP

    - ADC7 is now sampling port

    - speeded up ISR (int serv routine)

    - ADC clk_div = 16 (instead of default 128)

    - speeded up PWM DAC code

    - changed PWM mode to 'phase correct' PWM and F_PWM = ca. 31 kHz (= F_CPU / 510)

    - changed EEPROM write and read routines to Little Endian

    - (tried to) added TC converging scheme

    - experiment with EMA and DEMA (double exponential moving average)

    - keyboard input is read once


    What my GPSDO does now: It starts up with a low time constant (TC = 16) and when a lock is achieved the TC increases periodically and converges to the (from what I understood from the whole EEVblog-thread) optimal TC for the configuration.


    The TC itself is also part of a seperate PLL in a sense it calculates the DEMA of the 'ns values' (most left column). The DEMA has to be within certain limits. When the DEMA falls 'out of lock' the TC is decreased.

  • MY QO100 SETUP

    SV1BDS Yes, your chip number is 1 higher than mine but I was not satisfied with the results. However, that also could have been caused by the 10 MHz TCXO (old Philips type) I used.


    I now use the Ublox NEO-7M in normal PPS mode in conjunction with an OCXO and Arduino to provide a rock steady low phase noise / non-jitter 10 MHz reference signal.

  • What diode for harmonic generator to check LNBs?

    I don't press PTT. In RX mode there is enough signal at the 24th harmonic.

    Beware that some (older versions) go into an alternating 'on off mode', but that can be circumvened (for a while) by pressing the menu button.

  • POTY and return loss plot

    OK, the news is out (see my previous posting). Received nr 1 and nr 2 from Hans this evening. Just inserted nr1 and nr2 here. Compared to my benchmark (nr3) nr2 is on par and presumably somewhat better. However, the NB-tpx beacons are suboptimal to do absolute measurements due to QSB (can be 3 dB) and non-FSK (for the CW-beacon) and/or varying amplitude of the PSK-beacon.


    I decided to leave nr2 in to perform longer term measurements.


    Having tested around 13 different lenses, nr2 is an outlier in a positive sense!

  • POTY and return loss plot

    Just received some information concerning measurements of various dielectric lenses. Two lenses performed equal/better than the original Rocket Lens in a sense of gain (read: opening angle).

    I get two samples which I will try.

  • POTY and return loss plot

    The supplied lens with the POTY-kit is my '2nd attempt' for a lens. It worked/s better than the first attempt (this was a smaller lens) and improved SNR with around 3-4 dB compared to the open waveguide in conjunction with a f/D = 0.6 60cm wide dish.


    I still have an original Rocket LNB lens which performs (still) the best.


    I received a prototype PTFE PZK-lens and will measure that later on.


    It also seems that (in my case!) under illuminating the dish improves SNR because

    the overspill does not look at 'warm' objects.


    Anyway, lots of experiments to improve the station .. which is part of the fun imho

  • NB passband monitoring

    Don't think this broad signal is/was intended to play 'Band Police'. I reckon it is merely 'an experiment' to see what impact could be realized on the NB-tpx.


    It is clearly a loud signal, I call it the (injection locked) 'microwave oven', but what it is in reality .. no idea.

  • POTY and return loss plot

    ok1phu Fully agree with G0MJW (also concerning polishing the antenna ; -)


    Serious now: plots look good. Issue is that nowadays people have (relatively cheap) VNA's and are able to see details that only 'super' professionals were able to see 10 - 20 years ago.


    In the uWave HAM-scene there was a golden rule for decades: "When you've 10 dB RL it's enough"


    Now we're able to measure RL with 0.1 dB resolution and 1 Hz precision.


    IDEALLY the 'bult' between the dips has to coincide with 2400 MHz but in practice this is hard to accomplish. When you've a RL in the order of 15 - 20 dB @2400 MHz it is ok.


    Yes, it is not the theoretical optimum.

    Yes, you might loose axial ratio performance of a few cB's (centibels)

    Yes, you may not sleep with this 'loss'

    Yes, you feel uncomfortable


    but ..


    Yes, people who just do it [ (c) Nike ], get on the air, have fab signals, make a lot of QSO's, have a lot of fun and .... have nice dreams afterwards ; -)

  • POTY and return loss plot

    Solving the problem with duplex, I don't think so. Others use this antenna e.g. with ATV on the WB tpx in duplex mode with success.


    Anyway, I am curious what your perceived performance is when the 'Erreger' makes LHCP (into a dish).


    Simulations and practice show that the antenna makes CP with a good axial ratio,