Posts by pe1chl

    Cannot say anything about the uplink sensitivity but the downlink signal certainly is very strong! This time I will not be limited by receiver sensitivity, that is for sure.

    (sometimes this has been an issue with earlier Phase3 sats)

    When the transponder is officially released of course I will try with my 2 Watts as well. Maybe it could work, especially before the aligators get there.

    However, with this bird there should not be a reason for being aligator.

    Yes it sure is switched on :-)

    And now there is only a single carrier so it is not easy to judge what would be the S/N per QSO later, but when they saturate the transponder the signal is 50dB above the receiver noise, and when they reduce power like now the transponder noise is some 15dB above my receiver noise....

    Probably now most of those RTL2832 devices are used for generic SDR purposes instead of the original purpose of DVB receiving with FM/DAB as side function.

    It is a bit sad that all the production volume now goes into these devices instead of a device optimized for SDR (some more bits in the A/D, no DVB decoder) that we probably could have got for the same price when produced in this volume...

    But anyway, it is incredible technology for the radio enthousiast.

    Exciting times we are in.. I wish I would be young again.. :P

    ... rings Peter in 1983

    "Peter, do you want a receiver that will receive from 25 to 1700 MHz, all-mode, will decode sat telemetry, and give a panorama overview of the entire transponder? It will be 30DM. and, a 3cm converter to go with it for 15DM"

    I think you would have considered that two zeroes were missing :-)

    In commercial GPSDOs a "digital PLL" is used where the VCXO is driven from the output of a D/A converter which is set by a processor which performs the PLL function and loop filtering.

    With this setup one can remember the last D/A value used across powercycles, so the lock is obtained a lot quicker than with a fully analog design that has to find the correct control voltage from scratch after powercycle.

    Even with that, those units often require 30-60 minutes to fully stabilize.

    The signals are back to their initial levels here. Anyone having trouble to receive or identify them should try again... these beacons are 30dB above the noise here when viewed in gqrx.

    (I am currently using an 80cm dish and an unmodified StarCom SR-3602 LNB)

    Good morning,

    I am using here an Octagon Oslo Optima LNB and a sdr usb stick. As reference frequency source for both devices i made a small circuit from parts lying around which delivers 25MHz for the lnb and 28.8MHz for the sdr stick disciplined via gps

    Unless you have special requirements it isn't really required to discipline the SDR stick. Those "1 ppm TCXO" sticks e.g. from RTL-SDR.COM are stable enough for typical amateur communications use. Also because the stick is indoors at room temperature, vs the LNB that is out in the weather.

    But of course it never hurts to tinker and experiment :-)

    That sure looks impressive! (both the device and the theoretical background)

    Not so easy to reproduce, I'm afraid.

    It depends if you want to optimize for gain or for "spillover" which will result in extra noise when receiving (not what we are doing).

    Sure, but this topic was about "which TX amplifier to use" and with AO40 a TX amplifier for 13cm was not required (at least in the operational state that it has been in).

    So probably it belongs in a topic about antennas.

    This weekend my StarCom SR-3604 arrived, the 4-output version that I ordered intending to convert it to use an external reference.

    Because the housing has 4 F connectors, it will be easy to use one for the reference input, and have 3 outputs for the Phase4A receiver and my normal satellite settopbox (2 tuners).

    Now I opened it, I have seen something interesting: there are actually 2 separate 2-output legs in this device, each with a PLL/mixer chip of type "1051" (I have not found anything about it yet) sharing a single unmarked crystal (probably 25MHz like the marked one in the SR-3602).

    I'm going to try to convert one leg to use the external reference and a single output, and keep the other leg on the crystal. So I can watch TV without the reference connected.

    (there are 4-output PLL/mixer chips as well but apparently they did not decide to use one of those)