Upgraded system not syncing

Check that dbpr bootconf shows ODUstatus = EXTERNAL
This will verify that your save -o 2 has worked

Check that tclgets shows PCRReceived TRUE
This will verify that you are aimed at the correct satellite and not some nearby satellite with a similar outlink carrier.

The symptoms point to a transmit problem. All I can suggest is some questions..

Is the transmit cable connected at each end ? The centre wires at the F plugs must be long enough to make contact inside the sockets. 1.5mm proud of the F plug rim.
The braids should make good contact.  Make sure there are no braid fragments shorting the cable.
Is the external power supply switched on ?
Does 24V appear at the BUC end of the cable ?
Does the BUC get warm ?  It should consume up to 50 watts DC power (2 amps at 24V)
The BUC will mute (block its output) if the 10 MHz reference is missing or if the local oscillator in the BUC is unlocked.
A modem output setting of -t -18 means the output power is -9 dBm.  The input to the BUC should not exceed -20 dBm, so I presume you have a fairly long cable ( approx 11 dB attenuation ).
If you have a rather short cable I would use an initial power setting more like -t -48, meaning modem power output of -24 dBm.  Your hub should have no difficulty at all (*) detecting a CW carrier of say 0.4 watts. (assumes 6 dB loss cable)
It is important not to overload the BUC.  If you do you may damage it, the DC power drawn may be excessive and your external power supply may trip OFF.
Does the whole system work normally if you substitute the old 3W BUC ?
Your 2.4m dish should be 6 dB better than a 1.2m dish.  But this will only be the case if the dish is not distorted. Put tight strings or fishing lines up/down and across the front. The strings should just touch (1mm gap max at 14 GHz). Several dB gain loss will occur if the dish is distorted due to the weight of the feed/BUC assembly.  Where there are joints in the dish panels,the surfaces should be level either side.
Is the 2.4m dish intended for Ku band operation ? A white plastic C band dish may have a poor quality wire mesh hidden in the plastic, unsuitable for 14 GHz.
Dish pointing should be peaked by moving off to equal degraded qualities either side and the mechanically centreing.  Count turns/flats on the elevation nut. Do equal winding in of both azimuth nuts after getting equal side levels by swinging sideways to rest against each nut alternately.

Changing from a 1.2m dish to 2.4m dish should improve your transmit signal by 6 dB.  Increasing the BUC power from 3 to 4 W should give a 1.25 dB improvement.

This 700k pdf installation manual https://www.satsig.net/linkstar/linkstar-vsat-rcst-installation-manual-2005.pdf has full details of troubleshooting transmit problems.
wxw

Best regards, Eric.

(*) a skilled hub operator with the right test equipment will be able to detect far lower levels of CW.

I was not aware of those PCR messages. Does the data suggest it is still waiting/searching ? Does is also say 'state=NCRSync'

Did your terminal do anything at all when the hub told it to send CW ?  Can the hub try telling the modem to reset so you can see if all the LEDs flash at boot up ?

Don't transmit CW by manual command unless the NOC says so and you are certain you are on correct satellite. Use a much lower transmit power setting for safety.

May be wrong satellite.  The modem can lock to a similar symbol rate carrier on an adjacent satellte even if the centre frequency is different by up to 2 MHz or so.

Best regards, Eric.

If you get the same receive results when receiving on the 2.4m dish then I think the problem is to do with the transmit level, external power supply, cable or BUC itself ?

Can you carry the entire 3W feed system across to the big dish ?

Best regards, Eric.

Hello Tim,

Can you please tell us what is the model of the old BUC you had? Maybe one of them is extended Ku and the other is regular Ku for example? Maybe they dont have the same LO?

Kind Regards,
Nimrod

Can you make sure with the NOC that the new BUC LO is ok?

I have +-24VDC at the BUC, and am lucky enough to have a portable spec an with a built in DC block.
I have been unable to get a useable connection to the NOC through the 3W BUC on the 2.4m dish. The NOC tells me that my transmit power is varying significantly.
I am going to take the RCST outside next to the dish to see if it is a cable issue. From there I think I'll attach all the feed components from the old dish to the new one, get it working, and substitute the new components in one at a time.

Best regards

How to peak up a dish.

Azimuth: equipped with an azimuth screw, sliding block and two nuts.
Loosen both nuts apart so you can gently swing the dish from side to side, to rest against either nut alternately, either side of the beam peak.
Measure the degraded, off-peak, quality accurately while rested against one nut.
Swing the dish against the other nut and adjust that nut till you get exactly the same degraded signal quality.
Repeat till you are certain that both degraded measurements either side are exactly the same.
Put the dish approx in the middle of the gap between the nuts.
Tighten inwards both nuts by equal amounts, counting turns and flats on the nuts. This will clamp the dish in the exact centre.

Elevation: long drive screw with one nut holding the dish up.  
Use this nut to drive the dish. Move up off the beam peak and measure a degraded level accurately. Mark one flat on the nut with felt tip pen.  Count down turns and flats to exactly the same degraded quality the other side of the beam peak. Half the count of turns and flats (1 turn = 6 flats) and wind the dish to the centre. Try to get an accuracy of 1 flat or 1/6th of turn.

It will normally take at least 30min to peak up the dish. Think in terms of the receive beam being very rounded on top and your problem is to get to the exact centre of this, so that the narrower transmit beam is centered. You can't peak up just by maximising the measured quality of the receive beam. Once near the beam peak, if you alter the position by 1 or 2 flats you will be unable to determine if the receive signal has got better or worse due to measurement uncertainty.  It is far easier to make the measurements well off the beam peak where the slope of the beam pattern is steep and 1 flat makes a distinct measurement change.

Best regards, Eric.

Dear Tim,

Following Hussain post,

Another basic thing worth checking (the devil in the small details..)

Did you make sure your BUC is connected on the right arm of the OMT? The LNB should be connected to the arm with the RTF and the BUC should be connected to the waveguide arm without a filter.

Did you make sure you are on the right polarity settings? (cross/co pol)?

Did you make sure the BUC is aligned correctly with the waveguide of the OMT and not penpendicular to it?