There's a difference between Rx/Tx antenna and normal ones? (1 Viewer)

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enb141

SatelliteGuys Pro
Aug 5, 2009
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Hi, I've seen recently that lots of antennas has some sort of Rx/Tx angle at the final of the dish, in the place of the LNB shown as above

2-4-meter-VSAT-Antenna-01.ashx


So I would like to know if those arms can be used for normal Ku band reception or we need to use another arm for that?

This is a normal one without that angled arm

GeoSat90CMDish


raven18fix07lg.jpg
 
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RimaNTSS

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Aug 9, 2013
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It basically does not matter what kind of arms are used. The most important is that arms hold LNB in proper position in such a way that LNB's phase center is co-located with antenna's focal point. It is also important that LNB is pointed to the right place on the surface of the dish.
Rx/Tx arms usually made stronger to be able to hold massive block.
 

enb141

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Aug 5, 2009
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Thanks for your response, I'm wondering how an Tx-Rx arm can hold a normal LNB, as you can see in the picture I don't see how a normal LNB can be used in those arms, do they need any special LNB holder or something like that?
 

RimaNTSS

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Aug 9, 2013
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It is possible to fabricate proper LNB-holder. There are couple of pictures (can not find more ATM) where you can get idea how that holder can look like.

Add later: there is another picture IMG_20180428_111003 (Custom).jpg
 

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enb141

SatelliteGuys Pro
Aug 5, 2009
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How do you calculate the right angle and the right height?

It seems to be more complicated on those Rx-Tx arms than in those normal ones
 

RimaNTSS

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How do you calculate the right angle and the right height?

It seems to be more complicated on those Rx-Tx arms than in those normal ones
To now the right position of the LNB you have to know position of the focal point of the dish. And position of the focal point can be calculated (my preferred method) of measured. Yes, "normal arms" are simple but they not always position LNB in right position and it is not so simple to fix. Do you have in mind some particular antenna or original question was just rhetorical?
 
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RimaNTSS

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You are right a33, I like CM dishes. But never had 2.4m one. I have always thought that CM 2.4m is exactly 2400mm wide. Just recently I got information from couple of users that it is 2430mm wide, that mean that position of the focal point is in slightly different place than indicated on my collage . Antenna has 22.6* offset angle and it is beautiful piece of satellite equipment.
 

Cham

VE4GLS
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Dec 19, 2008
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I have a 2.4m CM disn I use for C-band. These are awsome dish reflectors, heavy duty and super well built to keep the proper surface shape/focal point. For Ku you can add an LNB holder. There are a few threaded holes on the "platform" you might utilize, or you can drill a new one for your particular holder. The BUC was likely a Ku up/dn link system, so if you can position your feedhorn in the same location should be a good starting point.
Attached 2 pictures, one of the 6" pole support I built with sked 40 and 1/4" plate, and the LNB holder I am currently using (actually using a C2PLL on this dish now for G13 127W NASA etc.. Last image showing dish aimed at 127. Black pipe under the dish is pvc conduit for the cable (hadn't buried it yet).

. 2.4msupport1.JPG 2_4dish7.JPG 2.4dish_complete (Large).JPG
 
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RimaNTSS

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I do not like multifeeds, but some people do, or maybe they have no choice to use them. There is new, length adjustable feedarms and multifeed for 1.8 Channel Master I made for a friend of mine. IMG_20180622_163715 (Large).jpg
 
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RimaNTSS

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After some experimentation, trials and errors I came to couple of solutions for Channel Master dishes. Namely, LNB-holder for original CM feedarms, and LNB-holder for new feedarms. Both holders, depending on the clamp used, can hold Ka/Ku/C-band LNB
 

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enb141

SatelliteGuys Pro
Aug 5, 2009
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Central America
Thanks for your input guys, now, if this looks so complicated, which plug and play LNB do you recommend me for this dish?

I'm talking about a universal LNB, do Rx-Tx LNBs can be used for TV Reception even if I only use the reception part of the Rx-TX LNB
 

RimaNTSS

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I would recommend to start from Inverto Black Ultra (IBU) or any other universal LNB. After some time you can do more trials. IBU is one of the best LNBs on nowadays market, it has good parameters and also not so expensive .
 

enb141

SatelliteGuys Pro
Aug 5, 2009
267
6
Central America
I would recommend to start from Inverto Black Ultra (IBU) or any other universal LNB. After some time you can do more trials. IBU is one of the best LNBs on nowadays market, it has good parameters and also not so expensive .

That one doesn't seems to fit by default in that Tx-Rx dish, I'm looking for a "plug and play" LNB for this Tx-Rx dish arm.
 

Cham

VE4GLS
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Dec 19, 2008
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Yes you can use the original BUC, but you would only have one polarity, and check that the LNB matches the frequency range you want.
 
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