Where to point antenna for milsat?

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mancow

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I generally have no problem picking up stuff using the D/M foldout antenna but I never really knew where to point it.

All the freq. lists show various names and codes for different channels such as Followon G18 Q31, Navy W4 N3, etc.... I'm trying to get a general understanding of what the designators mean and where I should point the antenna for maximum results.

I just finished building a set of director elements for the antenna to give it a bit of gain and I assume it would make it more directional.

I'm basically in Kansas City for a reference point if anyone has a suggestion.
 

prcguy

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The basic D&M or Trivec-Avant “helicopter blade” crossed dipole over reflector has about a 45deg beam width, which is not very pointy. The highest point in the sky for any geostationary satellite from your location will be about 45deg up when aiming due South and as you go East or West the elevation will decrease. When you see info related to a satellite it will usually give the orbital slot in degrees referenced to E or W. From Kansas you can expect to see satellites from about 30W (at eastern horizon) to 160W (at western horizon) if there are no obstructions near the horizon. Or you could buy my omni-directional Egg Beater RHCP antenna cut for UHF satcom and call it a day.
prcguy
 

mancow

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OK, that does help.

What known satellites are within view of the central US? Like with Inmarsat there's an AOR-E, AOR-W, etc.

Also, got a pic of that antenna?
 

prcguy

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Here is pic of an Egg Beater II cut for 260MHz. You can google search it to get the specs on ham radio versions. I scaled the ham version to the center of the UHF mil satcom band and had to make several sets of elements before the tuning was right. I tuned them with an HP scaler network analyzer as well as the 93ohm Teflon coax phasing harness. What a *****. It has an advertised RHCP pattern from near the horizon to maybe 50deg elevation, perfect for its intended purpose. I use a pre amp because of long feedlines but a short run of coax is fine without an amp. Make me an offer and I will take it down and ship it to you. I will also include the accumulated bird poopie.
prcguy
mancow said:
OK, that does help.

What known satellites are within view of the central US? Like with Inmarsat there's an AOR-E, AOR-W, etc.

Also, got a pic of that antenna?
 
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k9rzz

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Okay, doing some research, we're looking for AOR-W at 53 deg west, right? Is this the same bird as Intelsat 707 or just in the same place? According to Lyngsat.com, for someone near Chicago (me) that one is 135 deg. azimuth, and 30 degrees elevation (roughly).

Am I close?

I've got a 7 ft mesh dish already mounted that would have a good angle on that.


John K9RZZ
Milwaukee
 

prcguy

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Here is a blog that lists some of the UHF mil sat locations for the US and they are along the same arc that your dish is probably set up for.
http://mt-milcom.blogspot.com/2006/06/georgia-milsat-bandscan.html
If you hang a cross dipole at the focal point of your 7ft dish fed correctly for RHCP, it should give you about 13-14dB gain and a little less than 40deg beamwidth.
prcguy
k9rzz said:
Okay, doing some research, we're looking for AOR-W at 53 deg west, right? Is this the same bird as Intelsat 707 or just in the same place? According to Lyngsat.com, for someone near Chicago (me) that one is 135 deg. azimuth, and 30 degrees elevation (roughly).

Am I close?

I've got a 7 ft mesh dish already mounted that would have a good angle on that.


John K9RZZ
Milwaukee
 

k9rzz

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prcguy said:
Here is a blog that lists some of the UHF mil sat locations for the US and they are along the same arc that your dish is probably set up for.
http://mt-milcom.blogspot.com/2006/06/georgia-milsat-bandscan.html
If you hang a cross dipole at the focal point of your 7ft dish fed correctly for RHCP, it should give you about 13-14dB gain and a little less than 40deg beamwidth.
prcguy
Okay. I can probably get satellites as far east as 30W, but that's pretty low to the horizon for me. I'll give it a go since I've got a large tree branch, too high to trim, that's blocking my C-band reception for the 'good' part of the arc. May as well try the dish in this application. (always thought of lugging it on the roof for UHF TV ... but THAT would be a chore!).

THANKS.

John K9RZZ
Milwaukee
 

k9rzz

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Well, I tried a 250 mhz dipole at the feed point of my 7 ft dish. I unbolted the actuator so I could swing the dish quickly by hand. I could tell that the 255 mhz sigs were coming from a different direction than that 267.035 Spanish radio feed (about 90 deg vs 120 or 130), and I could even peak on the GOES East bird on 137mhz (although still not very loud). I wasn't hearing anything with peaks at 30 - 50 deg west though. I had it mounted within 1/2 inch of the C band feed so I must have been close to the focal point, and I could play with the polarity. Overall, I wasn't impressed, I can hear better with a flat reflector mounted behind the dipole. Will have to cobble up a RHCP feed.

Does anyone know if these birds are 'hemisphere' broadcasting, or more spot beams?
 
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