I have a client who has a C-band antenna that is somewhere around 11 years old, manufacturer and model unknown. Prime focus, 12 foot diameter, solid fiberlgass, az-el mount. The current feed is a Chaparral, single polarization C-band (no polarotor). There are no markings on it aside from "Chaparral" and "Patent Pending" The feed is not adjustable in any way (polarization, focal distance, scalar ring, etc.). As is typical, the feed is supported by four legs coming off the face of the dish.
The dish was originally looking at AMC8 (139W), way low on the horizon here on the east coast, receiving Vpol. I moved it to G16 (99W), receiving Hpol. After moving the dish and rotating the feed a nominal 90 degrees, we got a decent signal on the receiver (digital), but whenever something strong came up on an adjacent transponder (as viewed on the specturm analyzer), cross-polarization interference was so severe that we lost lock. Due to the design of the feed, there is no way of nulling out the cross-pol. There is no way of rotating the entire feed in small increments; there are only a few sets of fixed holes drilled around the feed to which the legs can be attached using angled brackets, so at best you can make rotational changes in very large (30+ degree) increments.
Other C-band dishes with fixed-polarization feeds I've installed in recent years (Prodelin and Comtech come to mind) all had a way of rotating the throat/LNB to adjust the polarization, and likewise the focal distance. This one doesn't have that.
It's apparent that whoever did this install originally was, well, not exactly first-class. Half of the hardware they used was stainless, half wasn't, and after 11 years, that which isn't stainless is now a rust blob that WD40 has no chance of saving. The feed wasn't mounted properly to begin with; one of the holes they used to mount the feed was the wrong position, i.e. all four legs/holes weren't separated by 90 degrees, so the feed and the leg attached to the "wrong" hole were askew. I'm not even sure if this was the correct feed for this dish to begin with.
Anyway, long story short, I'm trying to find a replacement feed that is fully adjustable. Unfortunately, we were rushed to get off the high-rise roof where the dish is mounted due to rain and I forgot to measure the focal distance before removing the feed to take back here to the shop.
Any words of advice or recommendations on a particular manufacturer or model? I've been searching the web and have found feeds that potentially could work, but nobody seems to put their manuals on line, and it's hard to tell from the pics whether or not they are fully adjustable/rotatable.
Thanks.
--- Jeff
The dish was originally looking at AMC8 (139W), way low on the horizon here on the east coast, receiving Vpol. I moved it to G16 (99W), receiving Hpol. After moving the dish and rotating the feed a nominal 90 degrees, we got a decent signal on the receiver (digital), but whenever something strong came up on an adjacent transponder (as viewed on the specturm analyzer), cross-polarization interference was so severe that we lost lock. Due to the design of the feed, there is no way of nulling out the cross-pol. There is no way of rotating the entire feed in small increments; there are only a few sets of fixed holes drilled around the feed to which the legs can be attached using angled brackets, so at best you can make rotational changes in very large (30+ degree) increments.
Other C-band dishes with fixed-polarization feeds I've installed in recent years (Prodelin and Comtech come to mind) all had a way of rotating the throat/LNB to adjust the polarization, and likewise the focal distance. This one doesn't have that.
It's apparent that whoever did this install originally was, well, not exactly first-class. Half of the hardware they used was stainless, half wasn't, and after 11 years, that which isn't stainless is now a rust blob that WD40 has no chance of saving. The feed wasn't mounted properly to begin with; one of the holes they used to mount the feed was the wrong position, i.e. all four legs/holes weren't separated by 90 degrees, so the feed and the leg attached to the "wrong" hole were askew. I'm not even sure if this was the correct feed for this dish to begin with.
Anyway, long story short, I'm trying to find a replacement feed that is fully adjustable. Unfortunately, we were rushed to get off the high-rise roof where the dish is mounted due to rain and I forgot to measure the focal distance before removing the feed to take back here to the shop.
Any words of advice or recommendations on a particular manufacturer or model? I've been searching the web and have found feeds that potentially could work, but nobody seems to put their manuals on line, and it's hard to tell from the pics whether or not they are fully adjustable/rotatable.
Thanks.
--- Jeff
