will implement a Autotune later and send it to you for testing
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As I mentioned above, manual tuning in 5 kHz steps was pretty fast with Manuelās @Tysonpower new app. Most important was to set the start freq, then reboot to clear the Tuner Iconās Status TAB screen. When I got close, I receive Status with intermittent Lock, then tweaked the freq as before from the Custom TAB, little by little until I got a steady Lock. Then I could see the necessary additional offset and include it.
What sometimes puzzles me is after achieving a very small offset, it changes radically getting way positive or way negative after several hours, although I retain Lock throughout. Temperature would explain this, but I have seen it often during the day when temperatures remain pretty constant. Ken
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I think what you stated pretty much tells it. The temperature swings, especially in springtime, with the LNB being sometimes in the sunlight or in a shadow, wind variations and environmental temperature variations themselves all can affect the frequency of the oscillator, unless special means are provided to mitigate all the environmental effects. As @Syed stated, the Maverick, for example, is the extreme worst LNB we could use for this narrow bandwidth, as it already comes with the curse of Ā± 1Mhz variation in its LO. Even at Ā± 200Khz, as in our dual LO single LNB, you are seeing wide swings in offset. It appears to me that the only way we can get truly stable is with a TCXO LNB such as the Othernet Bullseye, which claims the amazing stability of Ā±10Khz in its LO. This is the only unit I have studied with this kind of stability that is priced reasonably for the experimenter, at $19 US from Othernet. Most other LNBs with a TCXO LO are extremely expensive, from $150 US and up. Disclaimer: I am not an employee of, nor compensated by Othernet in any way for this reply.
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hi all, may I ask a silly question ? On othernet DC is present the 22 kHz tone to switch from one LO to the other ( LOW-HIGH)?
hi maxboysdad, no the voltage only control vertical versus horizontal
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Correct. The tone changes the LO.
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@iw0hjz
I think Alberto is asking if the tone is continuously present from the Dreamcatcher to the LNB? Or is it pulsed at a certain rate? My own curiosity is along that line.
I donāt think I understand the question, but Iāll provide as much information as I can. The 22 kHz is not usually used by the Dreamcatcher. Without the tone, the default LO is 9750 MHz on an LNB with two LOs.
When the TI TPS65233 sends a 22 kHz tone to the LNB, the IC inside of the LNB switches to the higher 10600 MHz LO. If the tone is not present, then the LO changes back to 9750 MHz.
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I think you nailed it, for me at least. So the Dreamcatcher currently is not sending the 22khz tone to the lnb, and it operates on the default of 9750 Mhz.
Correct.
OK, I got it. So for the american beam 12.840 ecc GHz the DC itself switch on the higher LO .
tnx
sry 12.08ā¦ecc ecc
@Syed
Now I am a bit confused. If the lnb is using the lower LO 9750, the DC does not need to shift to the higher LO for the 12.0894 Ghz frequency. This is the Local Oscillator, and with the 9.750 Ghz it subtracts, producing 2.3394 Ghz to the DreamCatcher, Ā± the stability of the Local Oscillator in the LNB. Is this not correct?
There is another frequency conversion stage between the SX1281 (the radio) and the LNB. Each RF stage introduces additional stability/offset issues. In the case of the secondary IF and the SX1281, they both reference the same 52 MHz TCXO, which has stability of 2 PPM.
When the carrier hits the Dreamcatcher, it is up converted to a little over 2.4 GHz. This is actually unnecessary, but that second mixing stage is there, so it just bumps the frequency up a bit. Dreamcatcher 4 is a little different, since it passes the IF straight to the SX1281, as long as it is within the demodulation range of the SX1281.
Will the Dreamcatcher 4 have a TCXO LNB, or something like the Dual LO Single that we are using now?
In the interim, it will ship with the Bullseye.
Fabulous!
This may or may-not be better to the userā¦ My experience is the current signal is difficult to get an initial lock. Then my lnbf can vary in frequency by +/- 200,000 and still have the DC3 decode the packets. I agree the Bullseye should not ādriftā after acquisition.
The current software on the (Skylink 5.7 or 5.8) both seem to evaluate the incoming decoded data stream and adjust the AFC offset about every 5 or 6 packets received (probably some averaging algorithm). This also re-evaluates the ālockā parameter. This also changes if the āstreamā type is changed form āunknownā to āfilesāā¦ which happened a LOT when the audio stream was being broadcast (not a good thing).
If the lnbf drifts by more then the 200000 frequency, then lock is lost and it can take a ālongā time for the Skylink to re-acquire the packetsā¦ Manually adjusting the custom frequency seems to act very fast, but the Skylink analysis of the packets only āsometimesā get a lock after the 5 or 6 packets are evaluated.
My feelingā¦ more testing before saying the Bullseye is the best solution.