Octagon Oslo PLL LNB with external Reference
-
-
after two days of testing, with the operating transponder I can state that an unmodified Octagon LNB is perfectly suitable to receive the SSB, CW, BPSK telemetry and even JT65.
We followed satellites with fear doppler and spin modulation and we never gave up. That little bit of drift does not scare us.
Maybe I'll put a hood on my unmodified LNB, but I will not do any more.
-
Just added a PL902 between the Ublox and phase comparator.
Well .... it's a MASSIVE improvement! I'm astonished!
Still have some phase noise left compared to my normal reference, but I think this might be the loop filter. However the jitter is not audible anymore!
Claudio thank you for the hint!
Below close up of the modification.
-
happy to be helpful!
by the way Remco how did you solve the issue of the external battery to keep the memory alive when the ublox is switched off? I saw video where they were using a CR button battery: but cannot figure how long that battery can stand the load...
-
I use a ATTiny13 to program the Ublox with a string of bytes which puts it in 1 MHz REF-out mode
-
-
-
[Blocked Image: https://eu2aa.com/photo/EU2AA_RDA3566Q.jpg]
External TCXO 50ppb 25MHz, twisted pair PETV-0.2, multi-colored (dark red - on the case, golden - 25 MHz) is connected to the load 68 Ohm 0805, through 1000 pF 0805 served on 7 leg / RDA3566Q.
- the cable, even the thinnest, elementarily tears tracks from the LNB board with details ...
- soldered to pre-tinned holes, a 0.12mm tin, a thicker one does not climb.
It works stably, good gain.
I tried it on the 6th leg, it works too, but after a couple of minutes an instability appears, the gain drops by ~ 10 dB, then it gets worse ...
Power TCXO - + 12V 0,2A / 30mA - a separate wire.
with the lid closed:[Blocked Image: https://eu2aa.com/photo/EU2AA_OctagonSLO.jpg]
complete:
[Blocked Image: https://eu2aa.com/photo/EU2AA_OctagonSLO_3.jpg]
-
OK, I think I jubilated too early. I just placed the PL902 in between the Ublox and PLL and started listening to the CW beacon. a few moments ago I tried to build the reference into a housing and saw that the PLL did not lock. I measured the output of the PL902 and found a fuzzy signal.
So, I fooled myself yesterday and listened to my TCXO ('free running'), so no surprise I had no jitter (TCXO is already vy stable and accurate).
It seems that you've to 'program' the PL902.
When I go to the clockwork.micrel.com site, it shows that minimal output frequency (CLK0) is 5 MHz (!) with 1 MHz ref in. Now I have to figure out how to do this ...
-
Ok ... my frustration, I was not able to find essential information in the datasheet, is solved. It seems that the PL902 has to be programmed (by MicroChip?) for every design. It is e.g. possible to insert 1 MHz (jittery) refclock and get 10 MHz out.
I still have one halve of a HC390 unused, so that can be divided by 10 to insert it in my 'original' circuit. -
sorry!
-
No , no ... it's not your fault ; -)
-
-
On this Microchip page you find many different types..
-
got it... http://clockworks.micrel.com/T…gn/listing/search/DKpl902
there are 55 versions availabe.. e.g. PL902Q42USY has the following data:
http://clockworks.micrel.com/T…sheetsPDF/PL902Q42USY.pdf
5MHhz and 10Mhz
-
With some efforts (because it's very small!) I managed to decode the description, which is indeed K167 (also what I ordered). In the specific datasheet (Mouser) it appears to me this is the max frequency it can handle/produce with 2.5 V power supply?
-
http://clockworks.micrel.com/T…sheetsPDF/PL902167USY.pdf
you have a 25MHz device!!
-
I see ! OK, then I was to quick with ordering. I only downloaded the PL902xxx datasheet.
OK, did you already order, and is there a part with 1 MHz ref in and e.g. 5 MHz or 10 MHz out?
-
I just check the 55 sheets.. I will response after that..
-
ok.. i think the best fit is the PL902Q42 link here:
http://clockworks.micrel.com/T…sheetsPDF/PL902Q42USY.pdf
Other devices handle 10MHz with different output levels:
PL902... 162, 169, 171, 177, 178
So next is to find the spec how to order a new type.. when I found this..we can make a perfect GPSDO type