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VSAT technology and installation >> Dish pointing and alignment >> waveguide combiner

Message started by DeanFM on Feb 17th, 2010 at 8:58am

Title: waveguide combiner
Post by DeanFM on Feb 17th, 2010 at 8:58am

I'm planning to buy a waveguide combiner on my C-band 4.5m hub antenna. the idea is to have 2 tx and 2 rx port using the same C-band. anybody has recommendation?


Title: Re: waveguide combiner - 4 port C band feed ?
Post by Eric Johnston on Feb 17th, 2010 at 10:45am
I would recommend talking to the antenna supplier about upgrading your existing feed system. If your feed parts have a manufacturer name on them contact them also.

If the price is quite unacceptable and you want to consider a cheaper, but technically risky, alternative contact other suppliers of feed systems, such as:
The feed you need must meet the cross-pol spec for the satellite system you are working to (e.g. 30 dB, not 15 dB)and it must be physically compatible with the horn flange etc.  The overall performance will not be assured and you may find the result not acceptable.  

The feed horn must always match the antenna exactly. The design, and location, of the feed horn, subreflector and dish are all inter-related and you must not alter anything.

( I think you are talking about needing a 4 port C band feed with 2 x TX and 2 x RX ports, rather than a phase waveguide combiner which might be used to merge the power from two HPAs or BUCs into one transmit wavegude, to make the total power needed and achieve excellent reliability with no-break, soft degradation in the event of HPA failure.  I've amended the title of this post - correct me if I am wrong.

Phase strip line combiners are used inside BUCs to merge the power from several output transistors together.

There are at least two other types of waveguide combiner:

3 dB coupler combiner:  this merges two waveguide but you lose half the power into dummy loads. Cheap and wide band, flexible so you can put carriers at any frequency.

Frequency/filter multiplexer combiner: this merges 2 or many waveguides into one, via filters.  e.g. Used to connect 8 HPAs, one for each transponder to one transmit waveguide.  Used on the satellite itself for the downlinks.  Very expensive, negligible loss, pretuned and restricted frequency ranges. )

Best regards, Eric.

Title: Re: waveguide combiner
Post by DeanFM on Feb 18th, 2010 at 4:14am
Hi Eric,

my antenna is a Suman 4.5m. Actually I want to transmit carriers from 2 BUCs using the same feed. the idea is to have a redundant in RF. what do you suggest?

Thank you and best regards

Title: Re: waveguide combiner
Post by Eric Johnston on Feb 19th, 2010 at 4:54pm
The use of a device like that below will allow two BUCs to be operated simultaneously, each with a different transmit carrier from its own modem and the output at 14 GHz combined.

Read more:
Unfortunately there is a 3 dB loss, so only half of the power from each BUC will reach the feed.
choose a coupler that works over the bandwidth you require.

You also need a suitably rated finned dummy load to terminate the other half of the total power at the unused port.
Read more:

Search Google for waveguide couplers and waveguide loads. Explain to the suppliers exactly what you want to do and get their assurance as to suitability of the proposed parts.

Best regards, Eric.

Title: Re: waveguide combiner
Post by DeanFM on Feb 19th, 2010 at 5:16pm
Thank you for your information, Eric. It helps alot

best regards

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