SatSig topic:

10 MHz Reference for iDirect hub and BUC

(Read 14791 times)

Oct 18^th, 2015 at 11:57am

HI any body here for iDirect HUB 5IF expert:
---------------------------------------------------
Now connected Terrasat BUC ( LO: 7375) but i want change the BUC to Belcom ( LO: 4900). If i want change then jest change the LO from 7375 to 4900 ( Please see the pic) and more anything change?

Oct 18^th, 2015 at 12:30pm

It is not normal to try to use a stand alone iDirect modem as a source of 10 MHz reference. I suspect it might work, but be careful and see my comment in message further down about frequency accuracy and stability.

You should really use a proper 10MHz reference equipment.

A high power BUC, such as 80W, probably has inbuilt monitoring telemetry regarding things like power output level, temperature, power supply current, up-converter oscillator lock/unlock and mute status. If you turn off the 10 MHz TX reference from the iDirect equipment the BUC should signal "Unlock alarm", "Missing 10 MHz reference alarm" and "Output muted". These alarms should clear when the iDirect TX 10 MHz reference is turned on.

You will need a suitable power supply for the BUC. The iDirect modem may be damaged if you attempt to power the 80W BUC direct from the modem.

The power supply cable arrangements to the BUC are important. If it is a separate AC mains or separate pair of DC power supply cables then there is less problem as the L band coax cable will go from the iDirect modem to the BUC and be able to carry both the L band signals and the 10 MHz reference. If the power supply arrangements involve interfering with the coax cable then any combiner, splitter, DC block, power injector etc needs to be designed such that both the 10MHz and the L band signal can reach the BUC. Make sure all connections are perfect. You don't want AC mains or high current DC coming back along the BUC coax outer, or even the LNB cable!

80W RF is dangerous. Do not power the BUC unless the output is connected to the antenna or a suitably rated dummy load. Don't get any body part in front of the feed/antenna. Transmit to a satellite only under control from the NOC and start with low power.

Best regards, Eric.

Oct 18^th, 2015 at 1:30pm

Hi eric,
plz see the attached diagram. Trrasat 80W A/C power no need DC volt but need that BUC only10Mhz ref. Our iDirect Hub ( 5IF) not provide the 10Mhz ref thats why according Diagram use the X3 modem. Did the work ?
BR//nazmul

Oct 18^th, 2015 at 4:07pm

I think this is the specification for the Terrasat 4 way divider/combiner:
https://www.terrasatinc.com/documents/014CombinerDividerDataSheet020114.pdf
It is specifically designed for this application. Port 1 passes the 10 MHz (and FSK and L band if required). Port 2 passes the L-band but blocks 10MHz.

If it has N type sockets check that your plugs fit. The centre pin of 75 ohm N type plugs is fractionally too small to fit 50 ohm N type sockets.

I've looked at iDirect hub specifications and it seems that line cards only pass out 10 MHz when used in 12000 series hubs. You have a 5IF hub, not a 12000 series hub. I've looked at a picture of a 5IF/20slot hub and there were no RCMs installed at the back.

Ideally you should have a redundant 10 MHz reference, plus 10 MHz multi-splitter with outputs to all equipment racks at the hub teleport. These station 10 MHz reference supplies will then go to the iDirect hub and the Port 1 on the Terrasat combiner.

If you use an iDirect modem as your 10 MHz supply for the BUC, this is cheap solution with poor frequency stability. I would expect it to work but there may be problems with frequency accuracy, stability and reliability. It would be a good idea to have a hot spare available and it would be worth looking inside the modem to see if you can adjust the reference frequency module once it has warmed up for 24 hours and then every month or so. Adjustment may be possible using a small screw or potentiometer. If adjustment is not possible is there any way to get at the 10 MHz supply inside the iDirect hub?. Have you asked around your teleport to see if there is already a generally available 10 MHz reference distribution supply ?

Read more here: https://www.satsig.net/topics/satsig-topic-num=1366883151

Does anyone know the accuracy and stability of the 10 MHz from an iDirect modem, when it is free running and not in a network. i.e. used only for its 10 MHz output?

If this is true "The 10 MHz reference used at a remote site may derive its accuracy from the symbol rate of the outlink carrier from the hub. " then you have a problem and should get yourself a stand alone 10 MHz reference equipment rather than modem..

Oct 18^th, 2015 at 6:11pm

Hi,
Thanks for your ans.

I talked with equipment vendor of iDirect, they told us 5IF HUB there is no option 10 MHz ref. But Terrasat made the device if, there is no 10 MHz option of the BUC then can use IFU for 10 MHz go through to BUC advice from Terrasat. My quires, if IFU use for 10 MHz for BUC, if working then why will not properly X3 idirect modem go through 10 MHz to BUC with HUB syc?
if possible plz advice.

Oct 18^th, 2015 at 8:01pm

You need a highly accurate, stable and reliable supply of 10 MHz for the BUC.

I recommend a proper 10MHz source. I've used a pair of redundant ovenised crystal oscillators with no trouble. They need adjusting 24 hours after installation and then annually.

An alternative is a GPS locked device. You need a GPS antenna outdoors and the oscillator needs to continue and be stable when the GPS signal is occasionally lost.

Ask your iDirect modem supplier what is the accuracy and stability of the 10MHz from a modem when it is free running and not in a network.

Oct 19^th, 2015 at 9:02am

Hi, thanks for your ans.

If we can use IFU of Terrasat then did the get strong 10 MHz.
any body experience?

Oct 19^th, 2015 at 9:14am

Get hold of the specification/manual for your model of 80W Terrasat C band BUC. Read and see if it has an internal 10 MHz reference, as an alternative to an external 10 MHz reference supply. Some models have "Internal 10MHz reference option automatically switches to internal reference when external reference is not detected."

What does IFU mean ?

Oct 19^th, 2015 at 6:19pm

IFU is Terrasat device when 10 MHz not into BUC then use for this purpose.
https://www.terrasatinc.com/documents/PDF-22084-0001RB.pdf

I seem this webpage but I need your more helping quires, if possbile plz see the website and read, this is ok for strong 10 MHz for this goods ( IFU)
also see plz see the image above

Oct 19^th, 2015 at 10:18pm

Does your Terrasat IFU contain an 10 MHz Oven-controlled Quartz Oscillator (OCXO) ?.

If yes, your problem is solved.

Note: The front panel contains a small hole that is used to access a trimpot (when the OCXO is installed) that enables users to adjust the frequency of the 10 MHz reference signal.

Best regards, Eric.

Oct 20^th, 2015 at 10:27am

IFU is terrasat device when 10 MHz not into BUC then use for this purpose.
https://www.terrasatinc.com/documents/PDF-22084-0001RB.pdf

I seem this webpage but I need your more helping quires, if possbile plz see the website and read, this is ok for strong 10 MHz for this goods ( IFU)
also see plz see the attached

Oct 20^th, 2015 at 11:00am

I repeat: Does your Terrasat IFU contain an 10 MHz Oven-controlled Quartz Oscillator (OCXO) ?.

Since the inclusion of a 10 MHz reference in the interface unit (IFU) is an option you need to check with your order/delivery details and model number/options etc.

I would look inside. You may need to do this anyway to check positions of various jumpers. Look through the small hole (if any) in the front panel. Is there a visible adjustment trimpot for the frequency adjust?.

If you power up the IFU alone and not connected to anything else do you see 10 MHz on any outputs.

Do this only with a good DC block on the spectrum analyser input otherwise you may blow up the analyser.

Another question: Does your iDirect 5IF hub have any 10 MHz oscillators (RCM-A and RCM-B) in it ?

Oct 20^th, 2015 at 11:55am

Hi Eric,

I seem into IFU block diagram tuning switch. plz see the attached.

Oct 20^th, 2015 at 12:04pm

Hi,
thanks for your massage.
Yes, I think have OCXO ( i seem block diagram). iDirect told me that it will not provide 10Mhz from HUB.

Oct 20^th, 2015 at 12:50pm

Examine the IFU box to decide if you have the OCXO or not. The diagram is generic and assumes the OCXO option is installed.

If you have an OCXO in the IFU, it may be used to provide a 10 MHz reference to both the BUC and the iDirect 5IF hub(assuming socket J6 exists on the IFU and a 10 MHz input exists on RCM-A on the back of iDirect 5IF hub).

In this case the line cards will get their 10 MHz from the back of the 5IF hub and the LNB cable from one line card can have its 10 MHz output activated to an external reference PLL type LNB.

It makes sense to use one 10 MHz source for the entire system.

If in doubt, send me photos of the inside parts of the IFU and the rear view of your 5IF hub. eric@satsig.net

Oct 20^th, 2015 at 1:58pm

thanks for your message.
I will feedback to you soon.

Jan 28^th, 2016 at 6:44am

Hi any body here for iDirect HUB 5IF expert:
---------------------------------------------------
Now connected Terrasat BUC ( LO: 7375) but I want change the BUC to Belcom ( LO: 4900). If I want change then just change the LO from 7375 to 4900 ( Please see the pic) and more anything change?

Jan 28^th, 2016 at 10:27am

To deal with the different BUC LO frequency (changing from 7375 to 4900 MHz ) you need to recalculate the modem L band transmit frequency and also change from carrier inverted to carrier upright.

Example:
BUC LO=7375 MHz
Wanted BUC output transmit frequency = 6000 MHz
Modem frequency = 7375 - 6000 = 1375 MHz
Inverted carrier.

It is inverted in this case since the LO frequency is higher than the wanted output frequency and you are selecting the lower sideband in the BUC power amplifier. The upper sideband output from the mixer at 13375 MHz is hopefully not being radiated by the BUC !

BUC LO=4900 MHz
Wanted BUC output transmit frequency = 6000 MHz
Modem frequency = 6000 - 4900 = 1100 MHz
Upright carrier

Here are some examples of different C band BUCs, the RF output range and the input IF range and the upconverter local oscillator frequencies:

C band name Range (MHz) RF IF range LO frequency Std C 5850-6425 950-1525 7375 / 4900 Ext-Palapa 6365-6725 1075-1435 7800 / 5290 Ext C 6425-6725 950-1250 7675 / 5475 Full C 5850-6725 950-1825 7675 / 4900 Insat C 6725-7025 965-1265 5760 Insat C (Inv) 6725 - 7025 975-1275 8000

Please restore your original posting and image (far above) back to the original version.

Jan 28^th, 2016 at 1:08pm

this is 5IF Idirect HUB.

----------------------------------------------------------
BUC LO=4900 MHz
Wanted BUC output transmit frequency = 6000 MHz
Modem frequency = 6000 - 4900 = 1100 MHz
Upright carrier
-----------------------------------------------------------
so L- band freq 1100 Mhz which location put the freq into the HUB . I did not see any option of the 5IF HUB. only i seem LO option for BUC.

Did automatically convert the freq?

Jan 28^th, 2016 at 2:10pm

Eric is right about the spectral inversion,and then the software make the calculation (you do not need to calculate the L band frequency, is automatically) I'm not sure about the 10MHz, because the XLC11 datasheet doesn´t shown anything about transmiting the 10MHz beside in the upconverter configuration the option exist, I guess is only for remotes.

In our case we are using this

https://www.oscilloquartz.com/files/1357907121-da_453x.pdf

You just need to be sure that the power of this 10MHz is arriving with the correct level into you BUC +/-5dBm, or you will have CRC32/8 in 8PSK/16APSK

** image added by forum admin **

Jan 28^th, 2016 at 2:16pm

Ask the satellite NOC what is the transmit frequency you are supposed to be transmitting.

Disconnect the 5IF hub from the BUC.

Starting with just one outlink module on the 5IF hub set up the config software so you think you will be transmitting on the correct frequency. This may involve setting the wanted C band frequency and the BUC LO frequency. See the above message regarding the calculation happening automatically.

Calculate manually your hub modem output frequency. This is to confirm that what happens is correct.

Then connect a spectrum analyser, with a DC block, to the output from the 5IF hub. Check the carrier is at correct frequency, has expected bandwidth and that no other spurious signals are present from 15 MHz to 2.5 GHz. DC power and 10 MHz reference may be present. It is highly unlikely that your modem transmit frequency will be the 1100 MHz which was an arbitrary example only to help you with the maths. The frequency will be in the L band range, probably 950-1950 MHz.

Turn down the transmit level to minimum. Call the satellite NOC and ask permission to transmit. Follow their instructions. They may ask you to turn off the modulation so the carrier is on CW mode. Once you are clearly on the correct satellite, correct polarisation and correct frequency they will ask you to increase level in small steps. If anything does not seem right or the phone call drops out, turn it OFF !

Regards, Eric.

Feb 3^rd, 2016 at 7:45pm

Thanks for your reply. let me check and update.

Mar 10^th, 2016 at 8:22am

Hello,

I need help. Our HUB 5IF all remotes is alarming frequently ( CRC). Please see attached.

Can you Please advice the what the region?

BR//nazmul