Upgrading a c-band dish / with polarity control.

[jrother]

Hi Folks,

I just moved into a new home that has a C-band dish set up and working. It's a 6ft Chaparrel with a servo controlled C-band only feed horn. I replaced the inexpensive LNB it had with a Norsat, and it gets great signals. I'm limited to this one dish. It came with the house, and is grandfathered in. My area won't allow any new dishes larger that a DBS dish.

I'm an RF engineer for a state wide radio network, so I have a need to monitor my narrow band commercial feed uplinks on AMC1 Ku.

I would like to convert this dish to where I can use it for my FTA hobby, but still be able to use it for monitoring my uplinks. The problem is I need to use a Ku LNB that is 10Khz stable, and units like the DMX741 don't meet the need. In addition, AMC1 Ku is currently skewed about 21 degrees from everything else.

Ive been looking at replacing the feed horn with something like a Chaparral Corotor II+ , and use the higher stability Norsat LNBs that I already have (the Norsats are single polarity LNBs).

Here is the rub, I want to be able to control the dish positioning motor, as well as the polarity servo to be able to tune my polarity even for AMC1 Ku, and have them in stored memory of a DiSEqC controlled positioner. I've looked at the G-box and V-box, but they don't do polarity. The only thing I have found that comes close is the Ashton Satseeker DS200. Sadoun used to sell them, but it looks like he dropped it due to lack of sales. Also as I understand it, the Ashton unit only does magnetic polorizers, not servo. (I'm not familiar with the difference between the magnetic vs. servo polorizers)

Is there a positioner on the market that I have missed, or any other ideas that may work.

 

[Magic Static]

I'd petition to put up a DBS sized dish as needed for your job. This one dish should not be included with entertainment system dish regulations. And should not be construed as a replacement to the BUD. I'm sure you could find a discrete spot to put it. Some people have special communication needs at home in connection with their professions and require special equipment ie a small ku dish.

Some of the guys here have built their own servo controllers. A small addon box. If you didn't care about the other ku stuff, you could stick a dual orthomode on there and skew the ku side. Just tossin stuff out there...

 

[FaT Air]

The new Pansat 9500HDX will operate a servo for polarity -link>> PANAREX And I think you'd be able to utilize OTARD rules for a 1 meter Ku dish for monitoring your uplinks. No need for both polarities, unless your uplinks are on both. Single polarity C120 flange feedhorn to mate with high stability LNB, For everything else FTA, Use the BUD with a G or V box and a 741 C/Ku LNBF or an Orthomode. No Servo, so a "normal" FTA rcvr will do. Or a Servo equipped feedhorn with C and Ku, Which would require something to run the servo, like the Pansat 9500HDX, Or the Bud for C band only and the 1 meter Ku on a motor with an Ku ortho. Just a few possibilities. I'm sure there are more.

 

[jrother]

I'd petition to put up a DBS sized dish as needed for your job.

Unfortunately, we can't afford the power level that DBS satallites use. I need at least a 1.8m dish for reception. I have used C-band dishes with a Ku only feed, and I know I can get the signal with a dish my size.

Some of the guys here have built their own servo controllers. A small addon box.

I've seen some plans for those, the two problems I see with the ones I found are that they rely on LNB voltage switching. The higher stability LNB's like full voltage all the time, and there are only 2 polarities, I would prefer 3.

Thanks for your ideas, This is the kind of brainstorming I was looking for

 

[jrother]

The new Pansat 9500HDX will operate a servo for polarity

I will look into this. I need a new receiver anyway. I've been out of the hobby since 2005, and my late 90's vintage Samsung receiver needed replaced anyway!

 

[Anole]

This LNBF is designed for prime-feed dishes.
Can you mount it beside your existing scalar (skewed of course), offset the dish east or west a bit, and still get your Ku signal.?.?
That's the easiest idea I can think of.
And cheap as heck to try.

edit:
If the stability is really a problem, we can find you a Ku scalar/feed/LNB to do the same job.
But, this would still be a good proof-of-concept.

edit:
The last three pictures in post #1 of this thread by Pendragon, show the skewed secondary Ku LNBF beside the main feedhorn.
It's a solution to the same problem you have: receiving AMC-1

 

[mikekohl]

Is your 6 foot dish a mesh or solid type? As a former employee at Orbitron Antenna, I can confirm that even a 10-foot mesh antenna has a hard time equalling Ku-band performance with ANY feedhorn, when compared to even a 90 cm solid offset Ku-band antenna. That size is sufficient for most Ku-band signals, and if you happen to be using MPEG-4 DVB-S2, utility type reception can generally get by with a 1.2 meter. Many of us are using Primestar sized antennas (under 3 feet) and getting good clear sky reception on the MPEG-4 DVB-S2 PBS channels on AMC-21 (Louisiana, Montana, Oklahoma). I would suggest something on the order of the Pansat 9500, or the Manhattan RS-1933, combined with a high quality 90 cm offset (to keep the legal eagles happy). Unless you are in a historic area or for safety reasons, I don't believe your community can legally keep you from adding a 90 cm (or even a 100 cm) dish. It should be a separate issue from something else that is already grandfathered in.

 

[jrother]

This LNBF is designed for prime-feed dishes.
Can you mount it beside your existing scalar (skewed of course), offset the dish east or west a bit, and still get your Ku signal.?.

That gives me ideas. I have a feed horn for a 1.8m offset dish, It wouldn't give me full illumination, but it should prove the concept.

If the stability is really a problem, we can find you a Ku scalar/feed/LNB to do the same job.
But, this would still be a good proof-of-concept.

I have 2 carriers side by side in a 600Khz segment. So yes, Stability is a big issue.

 

[jrother]

Is your 6 foot dish a mesh or solid type?

It is not an extruded (diamond shaped holes) type dish, It looks more like a solid dish with 1/16 in round holes in the surface.

I can confirm that even a 10-foot mesh antenna has a hard time equalling Ku-band performance with ANY feedhorn, when compared to even a 90 cm solid offset Ku-band antenna. That size is sufficient for most Ku-band signals, and if you happen to be using MPEG-4 DVB-S2, utility type reception can generally get by with a 1.2 meter. Many of us are using Primestar sized antennas (under 3 feet) and getting good clear sky reception on the MPEG-4 DVB-S2 PBS channels on AMC-21 (Louisiana, Montana, Oklahoma).

For the FTA, I'm sure your right, but at work, I have had to replace 1.2 M dishes and install 1.8 to stabilize the additional signals I'm trying to monitor. My signals are only about 10% the power of an FTA carrier, and I have 2 carriers in a 600Khz segment.

Unless you are in a historic area or for safety reasons, I don't believe your community can legally keep you from adding a 90 cm (or even a 100 cm) dish.

I'm in a situation that I have never dealt with before, I own the house, but not the land it's on. There is not much of a southern view from the house, no view to AMC-1. I can set up a portable 1.8m dish in the middle of the driveway, and get the signals, but that's not practical. The c-band dish is located behind the back yard. It sees the arc through a clearing in the trees for utility lines. The utility company / city owns the land, and monitor things back there closely. I'm not sure how the previous owner talked the city into this arrangement, but I don't want to loose it. they will let me "maintain" the dish. But not add anything. That's why I would prefer to keep the changes inside the LNB cover, if possible.

 

[FaT Air]

AMC1 is going to be replaced shortly by SES-3, since you have service on there, do you know if the skew on the replacement satellite is going to have the same skew? If it were to be "corrected" You wouldn't need servo control, and therefore, an orthomode feed is possible. (High Stab. lnb where needed and the rest FTA quality.)

how the previous owner talked the city into this arrangement

BITD, everyone was a little more "neighborly", I think.

 

[jrother]

AMC1 is going to be replaced shortly by SES-3, since you have service on there, do you know if the skew on the replacement satellite is going to have the same skew?

There is a clause in our contract that mentions that when AMC-1 is replaced, I will need to make adjustments to our uplinks. I suspect that this is to straighten out the skew.