Primestar / ChanelMaster oval Feedhorn

[Shawn95GT]

Can the Feedhorn itself go bad?

I swapped the whole feed arm from the 'new' dish to the old one to compare performance and I got absolutely nothing with the 0.8 LNB.

I'm going to play with it some more but I've been concidering picking up a C120 flanged Invacom (hopefully Quad polar) and using it with the CM Feedhord that is optimized for the P* oval.

I think part of the problem is that the 'new' feedarm is heavier. The transmitter (not hooked up!) out on the end of the arm is REALLY heavy. This might have deflected the motor / pole enough to mess up the arc for me.

I setup the orignal roof mount with some blocks to steady it. I'll take a shot at some sats tonight with it.

Now.... it could just be that this LNB is totally different that what is used for watching video from Ku. This LNB is from a 2-way satellite setup. I had set it to Std / 10.600 for the L.O. and like I said - I got nothing.

See this thread for pics of the Feedhorn / Feed Arm / LNB:
http://www.satelliteguys.us/showthread.php?t=71824

 

[rkrenicki]

Just take the transmitter off.. along with the transmit filter on the recieve side (as it will just introduce loss) and the waveguide setup.

Basically, take everything off of the feedhorn, and mount the LNB directly to it. I think that if you do not, that you will be limited to one polarity (as I think recieve and transmit are on opposite polarities on that setup, as dictated by the waveguide

Attached is an image if what I mean.

 

[Shawn95GT]

I totally forgot about the polarity issue. That it probably why I didn't see anything.

I'll take it apart tonight... The Transmitter is just dead weight on there.

Shawn

 

[rkrenicki]

You should crack that transmitter open, I am curious to see the inside of that

I keep trying to get my hands on a directway or starband dish for that purpose (well... that, and to have another nice dish)

Lost one yesterday.. got bidsniped.. ended for $3.25, my max was $3 at the time.

 

[Stefan]

What type of LNB is it? It may be that the LNB is designed to recieve only one polarity also. In fact if it's a WR-75 LNB (like used on a BUD). then it probably only recieves one polarity at a time and that polarity is deteremined either by a polarizing filter in the feedhorn or a polar servo. Anyway if it the LNB attaches to the feedhorn assembly with a rectangular flange that's probably what it is.

To get both polarities there may be 2 possibities. The first and easiiest would be to do exactly as Ultratryon suggest and simply use only the feedhorn itself, removing everything else and attach a C120 voltage switched polarity LNB (like the C120 Invacom you mentioned or a DirecPC LNB) directly to the feedhorn. Another possibility would be to use 2 WR-75 LNBs (meaning youd have to purchase a second WR-75 LNB). In this configuration youd still need to remove the filter which is in between the LNB and the "tee" (that probably not the proper name for it but hopefully best describes it) and youd need to remove the transmitting unit (BUC- Block UpConverter) and attach the second WR-75 LNB where the BUC used to be. Then youd need a switch to connect to the LNBs and switch between them. If I get time I may post some pics later that may give you a better idea of how such a configuration would go together.

 

[Shawn95GT]

What type of LNB is it? It may be that the LNB is designed to recieve only one polarity also. In fact if it's a WR-75 LNB (like used on a BUD). then it probably only recieves one polarity at a time and that polarity is deteremined either by a polarizing filter in the feedhorn or a polar servo. Anyway if it the LNB attaches to the feedhorn assembly with a rectangular flange that's probably what it is.

Exactly the situation.

I decided... "ok, then I'll just get get Horizontal and play with it"..... WRONG.

The square bolt pattern doesn't match that of the C120 flange. It's slightly different.

So my choice was to put it all back together and try that again, or take it all apart and shelf it until I get another LNB. I chose plan B.

The problem is... it is REALLY worth buying another LNB? If I buy a flanged Ku LNB I spend $40-$60 and might see a slight gain over my present setup. The 'bonus' is that the new feedarm has the nice DSS LNB mounts.

I could also buy the flanged quad-polar LNB from Invacom, use my existing feedarm and it's an even cleaner install.

I'm just thinking that any gains I see from using the matched feedhorn are going to be minimal. I could probably machine the LNB mount down so that the neck of my current LNB sits down another 3/8" to 1/2" and see the same gain. I think that the LNB being too high in the only inefficiency in my current setup.

I'm inclined to spend money on a 'real' dish (1.2M?) before another 0.3 LNB.

 

[Cascade]

I'm inclined to spend money on a 'real' dish (1.2M?) before another 0.3 LNB.

Do it, you won't be dissapointed.