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VSAT technology and installation >> iDirect Forum: hubs and terminals >> TAC login

Message started by ydh on Dec 12th, 2008 at 2:55am

Title: TAC login
Post by ydh on Dec 12th, 2008 at 2:55am
Does anyone know how to get a TAC login account?any price?


Title: Re: TAC login
Post by Scout on Dec 12th, 2008 at 11:06am
A TAC account comes with an active iSupport agreement with iDirect.

If you are a client of iDirect then you should have this.  if you are a customer of a customer, or an end client, it is very unlikely that you will get a direct TAC login account.  iDirect do not as a standard deal directly with end clients.

But if you could expand a little more on what you need the access for, perhaps the forum can give a more detailed answer.  Do you need to access software?  Do you want to open tickets (faults, issues, RMA's).

In short I would be very surprised if iDirect give TAC access to anyone who is not on active iSupport with them.

The other way to find out is to email them and ask.........

Title: Re: TAC login
Post by ydh on Dec 15th, 2008 at 8:45am
we have been operating hub for 2 years without knowing isupport is. yes, we need to access software, upgrade, and documentations related. any idea of the price (isupport)?

Title: Re: TAC login
Post by Darkside on Dec 15th, 2008 at 9:16am
There are three levels of iSupport: Basic, Enhanced and Premium. For software updates etc. you will need Enhanced.

The cost is based on a percentage of your hub equipment. Your company might actually have iSupport, email to enquire about that.

If you do not have iSupport, the best way to proceed is to contact your iDirect sales representative and ask them to assist calculating the costs and lead you through the process or you can send a email to, they will put you in contact with the right person.

Title: Re: TAC login
Post by Hamod on Mar 20th, 2020 at 10:28pm
Hi everyone,
I'm new in VSAT technology but i need your help on how to design a transmission plan/Link budget on VSAT link on a c-band and ku-band. This will go a long way in helping my career. I anticipate your response

Title: Link budget calculations
Post by Admin1 on Mar 21st, 2020 at 10:10am
I suggest you play around with this link budget calculator:

Try various dish sizes and transmitter powers and different satellite parameters.   Satellites with small spot beams will have high G/T on the uplink.

This index page gives many link budget examples and explanations of the various terms used.

Best regards, Eric

Title: Re: Link budget calculations
Post by Hamod on Mar 27th, 2020 at 9:38pm
Thank you Eric for your message.

I found out that increasing of the power in a comtech modem for example (cdm 570l) is not a power settings but a reduction in attenuation. How do i know i have saturated my BUC?

Title: Re: TAC login
Post by Admin1 on Mar 28th, 2020 at 11:25am
Determining the correct output power setting from the modem that will cause your BUC to saturate is not easy.

The purpose is to define the maximum value for operational use, that will never be exceeded. The value varies accoring to your cable length.

You will normally set the operational power somewhat backed off from saturation. The exact value will be told to you by the satellite network operations centre (NOC) during the carrier line up.

Typically the process will involve you chnaging to a specific frequncy and using unmodulated CW carrier.

Your modem output power level will be reduced to minimum and then increased in steps of 1 or more dB, while the carrier level is measured at the NOC. Initially the measured level will go up 1 dB per 1 dB.  This is called the linear operating range.  As the BUC input power reaches a high value the measured signal will start to go up by smaller increments.  If the NOC plots a graph of modem output versus measured satellite carrier the result will look something like this:

The key value is the -1 dB gain compression point, where the curved line falls 1 dB below an extension of the straight linear operation line.

If you are using a Comtech 570L then you may record the DC current and volts used by the BUC. Write these figures down as it becomes you only local measure of what the BUC is doing. (This assumes you are a VSAT and don't have a waveguide power tap on the BUC output and a Agilent power meter or similar. Teleports have output waveguide power monitoring and microwave spectrum analysers to measure any intermodulation when multiple carriers are used.)

BUC manufacturers normally tell you the guaranteed output power (watts) at the -1 dB compression point. The graph above shows a BUC specified at +3 dBW output but actually capable of +4 dBW, at it actual -1dB gain compression point.

I would still recommend using it only at +3dBW as this will give you a clean undistored signal and not exceed th manufacturers rating.

If you go above the -1 dB gain compression point the signal level will increase slightly as the BUC saturates, but the result will be interference to adjcent carriers and distortion of the wanted signal modulation and thus  reduction in quality (increased error rate). Further increase in input power to the BUC may permanently damage the BUC, so be careful adjusting the modem output power. It is important to avoid interference to adjacent carriers.

If you are desiging a link budget it is prudent to use generously rated BUCs so that in normal service the power out is perhaps 6 dB below the -1dB compression point. This gives a good margin for uplink power control to mitigate rain fades. Also, as time goes by the satellite operator may ask you to increase power.

Best regards, Eric.

Title: Re: TAC login
Post by Hamod on May 23rd, 2020 at 2:03pm
Could you please share with me how to interpret centre of box information. I have been given the task to select an appropriate time for the re-alignment of 6.3m antenna to the satellite and the satellite operator has shared with me the COB. I'm still learning. I await your kind feedback.

Title: Re: TAC login
Post by Admin1 on May 23rd, 2020 at 7:51pm
This picture below gives you an idea of how a satellite might move during the day.

The actual movement may be an ellipse and it may drift sideways slowly over a week or so. The view shown applies if you are on the same longitude as the satellite longitude. Elsewhere, the equator line will be tilted relative to your local ground horizon.

Ideally you want to aim a fixed dish at the centre of the intended stationkeeping box so that the satellite does not move too far from your beam centre.  If you call the satellite network operations centre they can tell you when the satellite is due to cross the equator, twice per day.  The east west position is more difficult as the satellite might drift sideways through the middle longitude less frequently, like weekly or longer.

Read more here: Inclined orbit operation

If your dish is large enough that the -1 dB beamwidth is the same (or smaller) than the stationkeeping box then you need to point a fixed dish very accurately and tolerate twice daily peak degradations. 

Useful Antenna beamwidth calculator

Best regards, Eric

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