TCXO Performance issues

Quote from PA3FYM

G0MJW Mike, changing the LO to 9.5 GHz results in a higher IF, lying more into the spec band width of the chip. Couldn't that be the 1.6 dB MER difference ?

No I don't think so as I also found other things that worked, even just a few Hz from 25 MHz made a difference, which makes me suspect it is related the Leo Bodnar reference division ratios. I also tried 24 MHz but that was not very good. The PLL multiple is 390 for 9.75 GHz (424 for 10.6 GHz) so if you wanted a 430MHz If you would want about 25.79MHz. I tried 23.59 MHz which puts the transponder on 23cms but it wasn't very good. Best for me seems to be 9.5 GHz.

Other LNBs may be and probably are different.

Mike

https://www.digikey.co.il/prod…025.0M/CW654CT-ND/1965862

Last time was tested 3 different LNB's with TCXO 25 MHz from VANGUARD. Not so good and not reccomend. Carrier not clear. TCXO mounted on PCB & filtered in DC very well . Tight coax inject 25 MHz. One interest point - not important selected port X1 or X2 on PLL, LNB will wake up. I'm testing with load capacitor or w/o - working in any case.

LNB model SR-320 consist of PLL RDA3568 (?) ,other models RDA3566xx

OCTAGON OSLO 1609 http://www.pabr.org/radio/lnblineup/pcb_oslo1609.jpg working even coax connected (include GND!) direct to PLL w/o load capacitors.

Attachet picture of transmitter with WG 10,489 MHz.

Test results of 3 LNB with replaced XTAL with TCXO. 2 types given good results - clear and stable signal.

OCTAGON 1609 with 7P-25.000MBP-T

STRONG SRT-739 with D75F-025.0M

VisionNET 300124 with D75F-025.0M

Can say only one - clear and perfect signal. In OCTAGON 1609 very important to inject TCXO to pin 7 (OSC2 or OSC Out) of RDA3566xx. Other LNB's not important. Coupling capacitor 4,7nF. Each TCXO have supply 3,3v from LDO. Capacitor across LDO 1uF ceramic 0805.