Do you have gain and beamwidth data for the helix?
Posts by DH1DA
you can use this board, click! : SI5351
I have one of these boards at hand and will make a prototype with it.
Thanks for your detailled explanation.
my clock generator isn't finished yet, but it works with DF7KB, who designed it.
OK, looks like it is a type A Chip in a 10pin MSOP. The datasheet says 25/27MHz at the crystal input, not sure whether this input will work properly with 10MHz from the OCXO. This is the reason why I have not tried this yet and why I was asking. Best will be to make a prototype myself and find out.
DC7KG Hallo Detlev,
welche Version des Si5351 verwendest Du und auf welchen Clock-Eingang geht die 10MHz Referenz? Funktioniert die Schaltung bereits?
Aktuell habe ich einen OCXO mit 2x AD9850 DDS Chips zur Erzeugung von 2 Frequenzen. Wenn der Si5351 mit 10 MHz sauber funktioniert, wäre das eine einfachere und billigere Lösung, die ich bei Gelegenheit mal testen würde.
in my opinion the transverters from Ukraine are good value for the money. They are OK to add new bands to your station, but you will not get a competitive VHF DX station for that price tag.
I have two of them (28MHz/70MHz and 28MHz/432MHz) and would buy them again. They are no high end products and you have to accept a number of weak points.
For me the oscillator stability was a real problem. The frequency drifts quite fast with the board heating up during transmission and cooling down during reception. Narrowband operation (e.g. FT8) was nearly impossible, so I added external OCXO controlled oscillators. If you want to use the transverter for SSB only, the drift is noticable, but in normal QSOs not really an issue.
Using computers for satellite operation was a great step ahead in the 80s. My first setup was a Basic program on a Sinclair ZX-81 with a Z80 core. I think that was 1981 or 82. It did only the prediction, no automatic antenna tracking, that was done manually.
Before we had to use an "OSCARLATOR" printed on paper. I wonder whether someone still has such an original Oscarlator. Would be nice to get a copy.
Hi Adrian, setting the electronic potentiometer with an arduino and some code is not that complicated and I was just about to do it. There are 3 large pads for GND, SCL, SDA, so the connection to the programmer is straightforward.
But then I discovered that the board layout is made for a mechanical potentiometer. Just solder it to the existing pads and move a 0 Ohm resistor to another place on the board. In my junkbox I found a miniature 1K pot form Piher, so the modification was done in some minutes and works fine without loosing the stabilisation and temperature compensation.
My unmodified amplifier had a bias of more than 2 A. Now it is set to 1,2A and this value remains stable even with the board heating up over time.
Adrian, many thanks for your prework and especially for your bias schematic, this was really helpful to check, whether there was a problem with the circuit.
To double the surface of a dish it is necessary to increase the diameter, however the focal length stays unchanged. Therefore the f/D will be lower. In your example f/D will be something like 0,3 ..0,35. A POTY feed will probably not work well in this configuration. To justify the effort of enlarging the dish, a suitable feed would be needed.
With 5-6 dBm from the Lime you can drive a MHL21336 module to get at least 1 Watt. This is low cost and gives a good signal without much distortions. The module is sold as used device on ebay for around 7€. Just add some cheap passive components and you get a decent amplifier. Check the other posts in this forum, where more details on the construction and data are given.
I use the same used OCXO with very good results. A simple 5V regulator and a potentiometer for the fine tuning is ok for the first test to check if the device is working at all.
To make full use of the OCXO capabilities you need to design the powersupply very carefully, to get high stability.
a bad import into Logger creates an error file called "bad.adi" in the main Logger folder.
Check there what is wrong with your ADIF data.
Maybe the frequency is in a different format. Logger uses 2400.000000 for 2.4 GHz.
Maybe you first have to edit the "Band / Mode" table of Logger.
See my example:
I have Logger32. It works fine and export data is accepted by LotW.
You need to make some settings: Bandplan for 13cm, prop mode = SAT and sat name = QO-100.
SWL-Max I have been using both of your methods. Given a reliable internet connection for the web SDR and a decent dish size for the local LNB + RTL-SDR, the results are not much different. Only a small additional signal delay of the internet connection is noticable. If you only want to listen and if you do not need the technical challenge, as mentioned by HB9SKA, then web SDR is fine for you.
You did not mention a 3rd method which is worth to test in case you plan to transmit. A modified LNB with a normal receiver, no SDR. This reduces the signal delay significantly. If you do not like to hear your own echo with a long delay try it.
For those who are interested in a LNB modification I can share a document with step by step instructions.
This is a mod for injecting an external reference signal over a single cable.
Here is the link: Mod-Documentation
@PA3FYM Hi, I have compared different register settings to generate a 1968 MHz LO signal for a mixer. One with FRAC and R=1 counter versus INT and R=25 counter. Reference is 25MHz in both cases.
The FRAC spectrum has heavy signals every 25MHz from the carrier, while the INT spectrum looks much cleaner wideband.
However close to the carrier (1...2 KHz) the FRAC gives about 6-8 dB lower noise compared to the INT.
I think for narrowband operation (SSB) the FRAC is the better choice, because the 25 MHz spurs will be filtered out after the mixer anyway.
What is your opinion and why do you suggest to work with INT rather than FRAC?
F4FDW Hi Laurent, I have a similar setup and the measured gain of an SPF5189 is only 11...12 dB at 2.4 GHz.
Unfortunately I do not remember the exact input power to my MHL21336, but if I drive it in the linear range, well below 1dB compression, the output is only 1W. Gain is at about 28..29 dB on 2.4GHz. So this confirms your observation.
Driving the module harder will probably give a bit more output power, but the signal will be distorted. In my opinion 3W in linear mode is not feasible at 2.4GHz. Maybe this works at lower frequencies for which the MHL21336 is specified.
I tested today with the QO-100 beacon transmission.
Current version is
SDRangel locks (stable constellation) and detects modulation and FEC parameters automatically.
However I get no video, nor internal in SDRangel, nor as stream (UDP).
My receiving setup with RTL-SDR should be OK, I am able to receive the beacon with the dvbs_gui software.
Did someone get a successful video and audio decode?
thanks for the detailled measurement results. Very helpful for my project.
Did you also measure port 3 --> 2 ?
ich habe 2 Goobay 67269 LNBs. Einer davon ist modifiziert und funktioniert sehr gut mit der externen Referenz. Der andere ist im Originalzustand und driftet langsam. Bei SSB muss man öfters nachstimmen. Ein schnelles Wobbeln kann ich nicht feststellen, die Sprachverständlichkeit würde ich daher als gut bezeichnen. Schmalbandige Betriebsarten sind aber ohne Modifikation nicht machbar. Den LNB habe ich vor ein paar Tagen bei Pollin gekauft, Preis aktuell 3,15EUR.