Posts by pe1chl

The PLL factor is 390. This means you have to be only 5kHz off at the crystal frequency to get an error like that. This is not unusual when the crystal cut does not match the circuit you are using it in. E.g. when you order a crystal for series resonance and in reality the circuit is for parallel resonance, or the loading capacitance is different.

Fortunately it is always easier to pull crystals down than to pull them up.

So you could attempt to correct (part of) the error by using a small parallel capacitance or a small series inductor.

However, such pulling will reduce the stability of the oscillator, so it may be worse than what you have now.

Depending on your local bandplan this may be a quiet portion of the band.

(not here, it is the band segment where the FM repeater outputs are)

It looks like you have quiet weather there. Then, my freerunning LNB is quite stable as well. But the past days it has been rainy and windy, and then it is much less stable. The beacon locking helps a lot. You could try that too.

(or wait for a more ready-to-use solution)

Actually it would be my preferred option for them to sell and ship it...

I haven't heard anything back after monday, maybe i'll never hear anything after they evaluate the situation with the ATV LNB... (it has only a couple of orders)

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 I already experienced that... unfortunately there is no easy lock detect output.

And also, the loop has little "frequency pulling" capability. So I hope to use lock detect to adjust some parameters (between "capture" and "lock" settings) and/or implement some search mode that activates when lock is lost.

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.

It could be considered to use the lower beacon as a reference as well.

Once locked on the upper beacon you can lock on the lower beacon with a much smaller bandwidth, especially during the long carriers.

But I should say it already works quite well here on my 80cm dish. It does not only compensate for the slow drift but also stabilizes most of the faster jitter.

Oh that is really great! We should make some friends there

Even a formation making it possible to locate in a single pass...

Interesting information!

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.

I modified the flowgraph to read from an RTL stick and got it working!

Very nice. Now let's see if it can be integrated in gqrx...

At least the experiment (also with gr-satellites) got me a bit more accustomed to gnuradio-companion. That is important because the first steps only lead to error messages and frustration

Is the hardware capable of doing that? Not all tuner cards are equal.

Those tuners used on the Minitioune Express are kind of special, see the postings of our Chinese friend.

Quote from i2NDT

there was such a thing onboard thr ISS: https://marconissta.com/

unfortunately it was disconnected in early february...

That looks very good, I now remember I read about it but I forgot to relate it to this usage.

Of course a polar orbit would be more optimal but this would do good as well.

As far as I understand it may be re-installed later.

Quote from DL1QC

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.

Quote from DL4OCH

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.

Quote from DJ7WL

Will be the banktransfer with IBAN and BIC possible?

I ordered mine last year and used IBAN euro banktransfer and it went smoothly.

You can send a mail to them and order the transverter and they will mail back an invoice with all the bank details.

Quote from DL5RDI

A built in TCXO would be nice e.g. 2ppm

I agree. When it comes to a technical discussion I will ask them about achievable stability with the internal crystal/TCXO.

Quote from DD0KP

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...

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)