Hello,
Simon Brown, G4ELI writes:
"As soon as Es’Hail 2 has been commissioned I’ll get a dish ordered and look at this issue."
Maybe SDR Radio could be the first RTL SW that integrates the software correction
That would be great.
vy73 DB8TF
Hello,
Simon Brown, G4ELI writes:
"As soon as Es’Hail 2 has been commissioned I’ll get a dish ordered and look at this issue."
Maybe SDR Radio could be the first RTL SW that integrates the software correction
That would be great.
vy73 DB8TF
pe1chl: TCXO stabilised RTL SDR sticks cost about 16€ here in DL, not so expensive.
And after a few minutes of warming up they are very frequency stable.
But clearly a solution with one stick ist best.
vy73 DB8TF
In HDSDR changing of the LO freq causes a short audio dropout, because of this you can only change the receiving frequency for locking on a signal.
A further drawback is that the signal in the upper RF window is still drifting, but on demodulating this signal it is no negative effect, only an optical issue.
Someday a clever person will programm a SDR software that is capable of locking on a signal (in the bandwith of a RTL-SDR) and on a second (following) demodulator you can listen to SSB. That would be the nicest and easiest solution
vy73 DB8TF
The difference is that your controller must send the Up and Down (or direct frequency ) commands via TCP instead of my mousewheel solution.
Direct freq control would be awesome fast. My solution can (only) tune about 5kHz per min.
But for sure this is working also very well
vy73 DB8TF
The HDSDR is a "stock" unchanged Version 2.76.
But would be work with any other SW which is capable of changing the frequency from an external source. I use the mouse scrollwheel in my setup.
The whole correction is done with a small microcontroller which measures the drift of the signal on the master PC and the slave PC is following and demodulating the audio.
No expensive GPSDO or fiddling (mod) needed around a standart PLL LNB.
vy73 DB8TF
The SW correction has nothing to do with my transmission signal!
The EBs or any other stable signal from the sat can be used.
Clearly the solution with 2PCs is not very usefull for portable use but as i mentioned already months ago on my hp i hope someday someone will write a sdr software which can run this correction with only one RTL SDR and one PC (portable RSPI).
But for now it is nice to see some measurements of various solutions to the drift problem.
For demonstration purposes i have uploaded a small video in which the running SW correction can be seen.
See it here. https://sendvid.com/liqktizj
vy73 DB8TF
Here i made a screenshot of the running SW correction.
Upper window is the signal from the LNB.
Lower right window is the AF output after SW correction.
Unfortunately the time span of the lower right AF window can't be set higher than 1m in the used version of HDSDR and with the newest HDSDR version the control via mouse scrollwheel doesn't work good.
But believe me the demodulated signal sits on 1Hz for hours.
vy73 DB8TF
Not bad, clearly good enough for SSB demodulation.
But the SW solution is far more stable
vy73 DB8TF
With two soldering irons or patinence (with one) it is not a problem.
The crystal has fairly large pins.
Vy 73
Here the measurement with a cheap TOYO TCXO "digital controlled" with a Octagon OTLSO LNB.
Useless for SSB.
vy73 DB8TF
here you can see the typical drift of an Octagon OSLO without any modification (TCXO/GPSDO) on a typical rainy and windy winter day.
The receiving NewGen SDR ist TCXO 0,5PPM stabilized.
VY73 DB8TF
Maybe someone is not waiting till we are officially allowed to transmit to the bird?
Those New.Gen SDR Sticks have even 0,5PPM TCXOs.
https://www.ebay.de/i/292700901426?chn=ps
I bought two of them and after 5 minutes warming up (indoors) there is no more drift measable. Opened one and verified, it is really a 0,5PPM TCXO inside.
If used with lock on a EB you can receive ssb for days without any retuning.
vy73 DB8TF
Here is an excellent PDF about helical feeds.
http://www.w1ghz.org/antbook/conf/Helical_feed_antennas.pdf
There he states that 4 turns are optimal for f/D 0,7..
Now who is right ?
VY73 DB8TF
thanks for the software
de db8tf
The BU500 is nice, but it has (at least the 2 i bought) a problem powering up if the supply voltage is a rising at power up.
I solved this issue with a small relais which switches the voltage on to the BU500 with a small delay when the voltage of the psu is stable at 12V.
The amp inside the BU500 could generate about 2W without problem but the bandpass filter is designed for 500mW max. So be carefull.
It could be a good idea to remove this bandpass and use a good lowpass after the main amp.
Also i did not get the "programming software" with the BU500 to change the LO frequency, but it is preset for 430MHz and thats fine for me.
The other specs and measurements of the BU500 are all good to excellent.
vy73 DB8TF
Is the sat spinning in the moment?
The beacon signal level is periodically (ca 30sek) getting weaker and stronger again.
vy73 DB8TF
18:56 everything normal again...
Here i found the seller of those cut out amplifiers:
https://picclick.fr/13cm-RF-Am…Watt-28-132765013840.html
French, not chinese
For use on 2,4GHz maybe the anaren filters are better removed?
Usually they are specified for 2,17GHz
vy73 DB8TF