Posts by pe1chl

    I am currently using the StarCom SR-3602 with the RDA3567 chip and it is OK, it wobbles but only dependent on the temperature. In quiet weather I can keep tuned to an SSB QSO quite well, but when it is windy and raining it wobbles.

    And of course it is not stable enough for digital modes.

    However, as with the other types mentioned here, I have heard that not all SR-3602s are created equal. Your mileage may vary.

    I also have a SR-3604 (4 output version) and it has 2 completely different chips, KTB1051, not a 4-output chip and not the RDA. I have not tested it with the satellite yet, only opened it to see how easy it would be to modify for external reference.

    (I have not been able to get datasheet or application note for the KTB1051)

    Currently I am experimenting with the beacontrack code from PE4WJ and this improves the stability a lot. Long-time drift of course is zero, but it also tracks the wobbling quite well.

    It appears that the LNB manufacturers just put in what is cheapest for them at the time, even under the same type designator.

    The more silly indicators like "Full HD", "4K", "0.1 dB" etc on the box the higher the chance likely is...

    But hey, look at what the price is!

    Yes and also the upper beacon is easier to "recognize". You would not want to lock on a CW station instead of the lower beacon, that is why first a lock on the upper beacon should be attempted.

    On a single carrier of course a simple PLL could be used. But as you mention, the signal is not continuous so the lock would not be continuous. Something would have to be devised so it will "hold" when the signal is not present.

    Well, I have no S/N problem to track the upper beacon. However, lock can be lost due to sudden strong excursions of the frequency that exceed the loop bandwidth at that time.

    I have attempted to add a "lock indicator" but have not yet succeeded.

    I don't think the description claims that this is a first or that it is unique.

    However, it is a bit different from other implementations in that it requires only a single stick (or other receiver hardware), thus it also compensates the drift of the SDR (not only the LNB), and it compensates at a high rate (many times per second).

    I have been running it while I was at work, tuned to the lower beacon, and when I came home it was still happily receiving CW at the same pitch (800 Hz). Very good.

    I don't see the static offset. When I tune to -125800 I hear the lower beacon at 800 Hz and when tuned to 123500 I hear the familiar upper beacon. Those frequencies are to be expected, remember you tune to the frequency of the suppressed carrier so any audio frequency you want to hear has to be subtracted from that (in USB).

    When you want to decode the upper beacon you do not need an entirely separate beacon receiver but you can start from the input- and output of the Costas loop.

    Indeed I am not yet declaring that this will be a success.

    Let's wait what the technician replies, salespersons are always enthousiastic.

    And see what kind of quantity requirement they have...

    I am not prepared to order 1000 pieces and then ship them myself. Not because I would not want to take the risk to order at a value like 5000 euro but because I don't feel like packaging 1000 units individually and ship them over 1/3 the world, receive payments for it, etc.

    But maybe other constructs are possible.

    They offer the DRO LNB for 3cm amateur band with 9 GHz LO, and sell it directly on AliExpress. But I do not know how that came about.

    On the other hand, I think every country has an interest to prevent illegal transmissions from it‘s own territory.

    I would not count on that. Maybe it works like that in Germany, but in many other countries the authorities are not at all interested in what happens inside the amateur bands, as long as it stays inside the bands and does not interfere with priority-1 users like broadcast, emergency services, air traffic control, etc.

    Besides, there are like 140 countries in the satellite footprint and a signal could come from any of them. So who do you want to inform? Doing that based on the language of a transmission is risky at best, as already pointed out above.

    And even inside a country it is very difficult to locate such signals with equipment operating on the ground.

    We have some experience here with a 70cm repeater with country-wide coverage (it once had 25 receivers and 5 transmitters all synchronized on a single frequency pair) and even there it was difficult to locate miscreants, in a search area that is about 5000 times smaller and with stations transmitting omnidirectionally towards the horizon instead of upward in a narrow beam at ~30 degrees elevation.

    There are quite some stations operating on QO-100 from my country but I do not hear any of them on the uplink. And this is just a small, densely populated country. Imagine what it would be for a large country.

    As we transmit up to the sky, worst in the WLAN area, it is from my point of view almost impossible to discover the transmitter.

    What would be required is a LEO satellite (polar orbit) that can receive on the uplink band and can do analysis of the signal. Of course it requires that the signal is persistent, like this one is. The satellite could be programmed to receive at a certain frequency and analyze the doppler. When it receives the signal it already indicates the general area (much smaller than the QO-100 coverage area) but combined with the doppler curve and a few passes it is possible to indicate the transmit site to within the precision required to go there and do local foxhunting.

    Remember there are dozens of cubesats being built and launched each year by universities and other research institutes who just want to build a satellite for instructional- or general "space research" purposes but are short of ideas what to do with it once it is in space. Especially when they want to use the amateur band for the telemetry downlink, they frequently ask "what amateur payload do we put on this to make this pass as an amateur satellite?". Next time, we could suggest to have a 2400 MHz SDR receiver on one or some of them.

    Target price should be 4,49 Euro for this version for 1K order. you know you can by a normal pll lnb at Pollin for 2,49 Euro...:thumbup:

    Yes I know :-)

    Of course price for a smaller production run with a manufacturer taking some risk will always be a bit higher. But I think even for 10-20 euro it would be easy to sell as many amateurs do not really like to pry open an LNB (how do you get it watertight again) and fiddle with SMD components.

    The special 10.0-10.7 LNB with 9 GHz LO is 18 euro. But unfortunately it is DRO based, otherwise it would already be interesting for QO-100 too.

    Yes I think so as well. Getting 1000 sold does not seem to be completely unrealistic.

    With the above parameters it could be used both for NB with an IF of 70cm or 23cm (only a bias-tee with 22 kHz generator required for 70cm, should be a simple project) and for WB with conventional tuners for 950-2150 MHz.

    But when people have other ideas to make it even more optimal I am all open to that. It still is in the phase where the salesperson is asking the technicians if it can be done.

    Well, that is of course the next step. First see if they can and want to produce something and if they want to take the risk themselves and sell it via Aliexpress (as they do for the 9 GHz LO LNB which I think is primarily target to 3cm ATV) or if they want people to order 1000 pieces and re-sell that themselves.

    (I suggested both options to them)

    It would of course be great when a shop like AMSAT or BATC would distribute them, and maybe add in some contribution money for the development of satellites.

    (other than that, direct ordering and shipment via Aliexpress of course will be cheaper and easier on the volunteers)

    I had contact with an Aliexpress supplier where I ordered another special type LNB (DRO type with 9GHz LO) and asked if they would be interested in producing a smallish number of special PLL LNB with lower default LO and capability for external reference.

    They appear to be interested in that.

    As a first proposal I sent the following characteristics:

    - PLL type

    - receive frequency 10.489-10.500 GHz

    - LO frequency 9.244 GHz or 10.049.88 GHz (same ratio as 9.75/10.6) (IF 439 MHz or 1245 MHz)

    - optional locking to external frequency reference (sent via the cable) of LO/390 or LO/424.

    - 20mm round waveguide with dielectric lens

    and provided them with some links to info about QO-100.

    Maybe people have other things to add to that?

    It would be a little worrying when there is a link to the FleetSatCom pirates...

    Before opening of the transponder I was already worried that those pirates might come over to our new satellite.

    In fact the army has put a secondary payload on a recently launched spy satellite which has the purpose of locating those pirates.

    So when there is more pressure on them, they might choose to find another place to operate and for some of them it could be QO-100.

    Let's keep a watchful eye, and maybe we have to consider to do the above as well...

    (that payload is an SDR receiver onboard a LEO satellite that uses doppler to locate the sources when flying over them)