External reference from ICS512 (PLL CLOCK MULTIPLIER)

Hello All,

FYI - some results of testing the formation of the 25 MHz reference signal for the LNB PLL and 40 MHz reference (for the VHF SDR ADALM Pluto) based on the ICS512 chip (PLL CLOCK MULTIPLIER) at http://www.ra3apw.ru/proekty/ics512_reference/. Please use Google translator.

The 10 MHz OCXO with phase noise -154 dBc / Hz @ 10 kHz acted as the main source of the reference frequency.

As a result: 25 and 40 MHz signals are formed, stability is good but the phase noise value (-99 dBc/Hz @ 10 kHz) is not good enough.
Use for QO-100 is not recommended.

73 de Karen, ra3apw

Hi SV8QG,

crystal filter can help to remove only harmonics from ICS512 but , unfortunately, will not help to make phase noise better...

73 de Karen, ra3apw

Alex, agree, I am not sure that it's a good idea to buy this "OSC101" board.

CTI OSC5A2B02 is a good OCXO for QO-100 station (I have the same in my QO-100 transverter).
I measured this 10 MHz OCXO's Allan deviation and phase noise (better than -150 dBc/Hz @ 10 kHz) - no problem and stable parameters.

IMHO, the reason of an issue is a PLL Clock Multiplier of previous generation on board. I made the similar test with NB3N502 few months ago and got PN level even 10 db worse that with ICS512.

73 de Karen, ra3apw

Hello Claudio IK1RQX,

I would like to be understood correctly - I expressed my opinion and indicated the reasons for such a judgment.

It all depends on the specific task - for example, if you want to make a frequency marker, then it is quite possible that such a solution with ICS512 will satisfy someone. Although the rubidium source provides good long-term stability but it is not the best accuracy.

But I expressed an opinion on a concrete solution - the use of ICS512 as a reference source for LNB's 9750 MHz synthesizer - in my opinion it is necessary to look for other solutions where two conditions will be fulfilled simultaneously - good stability AND low phase noise.

I am waiting new PCBs to check other ideas for this task.

Karen, ra3apw

Claudio,

I don't think that Si5351 is the right choice for this SHF task. I played with Si5351 five years ago (Si5351 spectrum) and have a result of the output spectrum measurement. Si5351 is not a low noise synthesizer but a clock generator.

Please note when a signal from Si5351 will be multiplied in LNB's PLL by 390 times the phase noise will degrade by 52 dB.

Karen, ra3apw

Claudio,

I think that for a good transceiver like IC-9700 you should use a good reference source but not ICS512.

ICS512 will spoil the parameters of the transceiver especially if it is supposed to be used in the contest position.

Karen, ra3apw

Hi Claudio,

Thank you for the link, I read it with interest.

I unfortunately do not have any experience with this device.

In my opinion, in order to make a decision about the choice of a reference signal source, first of all, you need to know two parameters:

1. Allan deviation
2. phase noise.

I did not find any information on this in either the article or in the lot's description.

Karen, ra3apw