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HX conversion for Channel Master dish

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Nov 24th, 2007 at 5:21pm  
I'm told that my new HX transciever may be mounted on my existing channel master dish, with the appropriate conversion kit.  Does anyone know what is included in this kit?  i.e. a dish-polarization mechanism, feed-horn and wave-guide spacer, in addtion to the mounting bracket?
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Reply #1 - Nov 24th, 2007 at 5:57pm  
I wish you luck. I'm attempting - with very little success I might add - to get very similar information from Bentley-Walker relative to upgrading a couple of my my Hughes OSIRIS rigs. Responses from two of their sales staff have been very disappointing. I've asked that they forward  my request to their technical people, will post here if I learn anything that may assist in your quest.

//greg//
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Reply #2 - Nov 24th, 2007 at 6:40pm  
forsberg

If you have a Channel Master dish you need to use a matching Channel Master feed horn, positioned at the correct distance from the reflector.

Consider the waveguide interface of the ChannelMaster horn.  It is probably a circular waveguide with flange with holes.

Consider the transmit/receive waveguide interface on the HX OMT.  Does is match up with the feed horn ?   If not, the kit you need is some waveguide spacer to allow the two to be attached to one another.  Have a look and work out what you want.

Further hardware will be needed to support the weight of the HX transmit/receive module.  You may be able to improvise, but be aware that you will need to be able to rotate the BUC/LNB/OMT/Feed for polarisation alignment.

Check with your service provider that the antenna system you propose will be acceptable to them.  You must satisfy them that your transmit gain, polarisation purity and side lobe pattern will comply.

greg

Have any of the US Direcway hubs yet been replaced or upgraded to be HX hubs?.  

Best regards, Eric.
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Reply #3 - Nov 24th, 2007 at 7:06pm  
Thanks, Eric,
That's exactly what I don't know.  (Is the wave guide spacer/conversion included in the Andrew conversion kit?)  Minimizing the lever arm on the existing channel master mounting bracket (that attaches to the feed horn wave guide) may be another issue, but a little home-made spacer will do the trick.

Another question:  Regarding Mounting the HX hardware on the channel master and older dishes...is setting the polarization on the BUC/LNB/OMT kosher, or does one have to rotate the entire dish as in the stock HX antennae.
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Reply #4 - Nov 24th, 2007 at 8:21pm  
Quote:
greg
Have any of the US Direcway hubs yet been replaced or upgraded to be HX hubs?.   

Nope, but that's not an immediate concern. Originally I was going to give Bentley-Walker one last chance for an informed response. Failing that, I planned to contact you offline for specifics. But that changed when this topic opened.

I'm personally only interested in the HX feed component(s) that will upgrade my ODU to a HX clone.  A little hardware change like that should be transparent to my NOC (hub). If it's determined that the flanges and waveguide channels are compatible, I might have a part or two that could assist FORSBERG.

//greg//
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Reply #5 - Nov 24th, 2007 at 9:05pm  
Greg

The part numbers etc for the outdoor equipment are:

LNB:   LNB types vary, e.g. Invacom or NJR.

BUC:   1032574-0001

OMT/Filter:    PN 110196-7  112440-003  Rev H 01-06-04 1500286-003

Yoke:    PN1500192-0123 2W-1M SN 100630603502 RevG

Here is what it looks like:
...

The feed horn and the tapered waveguide adaptor are Prodelin parts and are strictly associated with the antenna.  The tiny "505" on top of the feed throat and the single tick mark on the rear spacer flange must always be away from the feed support arm.  The fat lump on the underside of the feed horn throat must always be towards the feed arm.
...

The OMT and and grey transmit module are Hughes and the LNB is any suitable LNB.

Which parts do you want ?  

As shown, complete with the mode matched feed, you need a dish that is able to be rotated as whole for polarisation alignments as the flange interface between the OMT and the tapered tube is not a rotary joint and has discrete 60 deg screw attachment positions.

If you use the OMT and radio with other feed arrangements, such as Channelmaster, you can rotate the Channelmaster feed horn.

The new mode matched feed is a major breakthrough in polarisation purity performance for offset dishes but does require that the feed horn is always fixed in rotation so that the three mode matching slots (inside the fat lump) are oriented towards the feed arm.   Having fixed the feed horn you may then, for polarisation alignment, either attach an OMT at any angle using a rotary joint or at a fixed angle (e.g. 0 or 90 deg) plus entire dish rotation. Horizontal receive polarisation is illustrated above.

I have a Channelmaster feed here and will see tomorrow if it fits at the OMT interface.

Best regards, Eric.
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« Last Edit: Nov 25th, 2007 at 9:02am by Eric Johnston »  
 
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Reply #6 - Nov 24th, 2007 at 11:38pm  
As I suspected - but could not get BW to discuss - I need only the feedhorn and a tapered waveguide adapter. My Az/El cap does in fact permit +/-90 degree rotations of the reflector.

Linear polarization on my Prodelin 98cm model 1983 reflector is in fact accomplished by +/-90 degrees rotation of the reflector and fixed feedarm. I have two new 2w TRIAs; a "pure" OSIRIS, and an OSIRIS/TG2. I've also got a used 2w OSIRIS with motorized feed, but that's not a viable candidate for modification. Each of the new ones has a  Prodelin standard feedhorn. The "pure" model also incorporates a Prodelin standard (cylindrical) waveguide adapter.

As I suspected, it seems only feedhorn and waveguide adapter changes should be required to create HX clones.The tapered waveguide adapter you show should attach directly to my OSIRIS/TG2. The pure OSIRIS however, will require that the tapered waveguide adapter have a square flange on the OMT end.

The design of the TRIA bracket is such that there's no room to insert a flange adapter. I have digital photos, but do not have the wherewithall to post them here. They're being sent via email.  Included will be two views of the standard waveguide adapter, which may be of interest to FORSBERG

...
Above: Adaptor Front

...
Above: Adaptor Rear

...
Above: Az-El cap

...
Above: OSIRIS-TG2

...
Above: Pure OSIRIS

//greg//
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« Last Edit: Nov 25th, 2007 at 9:14am by Admin1 »  

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Reply #7 - Nov 25th, 2007 at 9:34am  
The new mode match feed and dish should be used as a pair together.  Details are:

Antenna:  1.2m Prodelin f/d=0.8 EUTELSAT:
0800-3264  1.2m RT 0.8 F/D W SHC & DW LOGO HNS PARTS 901226-0005 02/05/07 

Matching feed: 39 deg mode matched feed horn and circular waveguide spacer.
0183-721   ASSY 39 DEG EUTELSAT FD,

If you want to experiment with the new feed horn/spacer I suggest you get one direct from Prodelin.
Note that the feed diameter is suitable for a f/d=0.8 dish and the mode match function will have been designed to cancel the inherent cross-pol caused by the offset angle of the 0800-3264 dish.

Best regards, Eric.
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Reply #8 - Nov 25th, 2007 at 11:00am  
Thanks again, Eric.  I remain skeptical that this will work effectivly with a channel master dish, despite BW's assurances.

here are the pictures of the HX OMT, and the channel master feed horn flanges.  (Feed horn being about 1/4" larger than the OMT flange)  My Az-el mechanism also does not permit polarization adjustment, so I'd need one of those to make the conversion.

I may very well just order the 0800-3264 dish after all!

Thanks again for all the great info.

HX on left, hughes OMT on R.jpg

HX OMT.jpg
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Reply #9 - Nov 25th, 2007 at 9:29pm  
Hi

This is BW firstly there are hundreds of our customers using the Andrews dish with the official Andrew HNS ODU MTG KIT part number 611611017 , this 100% works perfectly with Channel Master and Andrews class 2 and class 3 Antennas . We have plenty of these adapters in stock and they come with the correct Feedhorn for the Andrews/CHMaster dishes.

As regards your enquiry Greg I would like to know who you spoke to at BW ? Nobody here knows anything about your query , I am sure you have seen my name on the posts and you can always mail me directly as I am sure you are aware , if you are not getting satisfcation I am ALWAYS approachable !

Regards your Osiris dish system I am pretty sure you dont need anything except the correct RX LNB if you want to get OUR service , I will check with Hughes tomorrow but tell me is it a 1.2 mtrs dish you have and is it a Ku Band BUC , part numbers would be helpfull , my email is Anthony@bentleywalker.com , I look forward to hear from

Best Regards A.E.Walker
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