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Inmarsat monitoring

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SCPD

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Does anyone know if there is any anlog traffic on the Inmarsat system or is it all digital now?

Craig
 

K0ATC

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I listen to Inmarsat quite a bit, there is still analoge traffic on it but not too much. I use a MTI umbrella dish with a PAR preamp. I have several of these setups and have sold a few in the past. Everyone says its the best way to go, the antenna comes from an inmarsat phone system. I enjoy listening to inmarsat there can be some really interesting stuff that comes across, most of which can not be repeated. There has been some shuttle related com's over the past few days as well.
 

K0ATC

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1.5-1.6 ghz in the middle. You need a good antenna and preamp, or LNB if you cant get that range. I used a AOR5000A but sold it recently, now I use my IC-20.
 

K0ATC

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Yeah thats what i was saying, LNB, its an preamp with a block converter, "Low noise block converter" You can bring it down to say the 2 meter or 70centimeter range. I just use an LNA or "low noise amplifier" because my recievers will pick up that range and i have several runs of LMR-600 coax that allow you to receive microwave band frequencies without as much coax loss. If your intersted let me know, i'll see what I can find for an LNB for you. I had my LNA built by Down east Microwave, i think i said PAR last time but those are some filters i bought.
 

K0ATC

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Give these guys a try:

http://www.downeastmicrowave.com

It may be best to call and tell them what you want, their site is very confuseing. Just tell them you want a preamp for inmarsat monitoring, they also sell antennas and whole kits. I see you have some aor's and Icoms that have the coverage so you wont need an LNB just an LNA. If your going to have a decent length run of coax give LMR-400 a try, its pretty cheap on ebay.
 

mancow

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I have:

Plenty of Anderew hardline and LMR400

Some feedhorns from direct tv or dish stuff

Various N connectors and other ends.

Metal and other odds and ends to build antennas

Service monitor to 2.1 Ghz with tracking and spec. an.

R-20 that goes to 3.3 Ghz

Can any of that be used to get something working, someting home built?

What would be the bare minimum? Could I find plans to make a dish and feed the R20 directly or is there alot more to it than that? Could the direct TV stuff be used as an amp somehow?
 

Napalm

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scott4957 said:
Give these guys a try:

http://www.downeastmicrowave.com

It may be best to call and tell them what you want, their site is very confuseing. Just tell them you want a preamp for inmarsat monitoring, they also sell antennas and whole kits. I see you have some aor's and Icoms that have the coverage so you wont need an LNB just an LNA. If your going to have a decent length run of coax give LMR-400 a try, its pretty cheap on ebay.
All my Icom's stop at 1.3GHz, and Inmarsat is 1.6, right? I still think I need an LNB/downconverter.

Thanks for the link I'll look into it.
 

K0ATC

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Napalm,

Thats right then you would need an LNB, which would take the place of an LNA. All an LNB really is, is a preamp that downconverts at the same time. Many that have the capability to listen at 1.5 still downconvert because of coax loss issues, so its not uncommon. Down east should still be able to help you out.

Mancow,

All that stuff sounds great, you are almost there. One of the old dishes, coax and connecters will work great. You will still need to build a feed for the 1.55 gig range which you should have no problem with, just search for inmarsat feed. I dont think you will be able to get a preamp out of that stuff, but they are not too expensive, and not needed right off the bat, but once you run coax any reasonable length you will need it. Without it the signal will be near or in the noise. Give it a try its a lot of fun!
 

mancow

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So, you are saying that I can just take off the dish feedhorn and put the modded inmarsat range stuff in its place?
For clarification, the dish I am referring to is one of the small 18" deals.

What about a home made dish? Could a guy make one?
 

K0ATC

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Yep that should do the trick, I'm not sure exactly how much gain you will get, but with a properly built feed i would say over 20db. I would not try to build a dish as they can be had for nothing, i get them off houses that no longer use them and people are happy to give them away, they dont want to see them up there anymore. I forget how many DB of gain my MTI dish is but you can look it up and compare. With a preamp it will be no problem. I even built my own helix antenna for inmarsat, but it is a pain in the butt and very time consuming. I would go with the dish, more gain and easy to build, try to find a helix feed horn, or plans for one that is. Try this link, though they didnt have the best luck, it will work im not too sure what they were doing wrong.

http://vlemmings.com/
 

mancow

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Sorry guys if I'm thread hijacking. If so just kick me out.

BUT I JUST REALIZED THIS.

I have a preamp made by Cellwave. Here are the specs from the supplied sheet:

PF9207A

Freq. 1453-1477
Input Vswr -19.6 @1475 Mhz Gain 16.45 dB @1453 Mhz

Output Vswr -21.8 @ 1452 Mhz Gain 16.48 dB @ 1477 Mhz

Noise Figure 1.457 dBm

Output IP3 38.7 dBm

DC power 245 mA @24 Volts



I currently have it up on an end of LMR 400 at the base of a 7 element 800 mhz yagi and it actually works good there. It's a night and day difference when I cut power to it down at the shack. I was surprised it worked that low.

I saw that there were two slugs inside that appear to contact or hover above two circuit traces. I must admidt I got sketchy and couldn't resist twisting them but it didn't seem to make a difference to the 800 reception.

I wonder if this could be used?

What do the specs say to you?


-----------------------------------------

Edit: if it's usable in conjunction with the other stuff I might make a trip to my dad's garage and grab that old Primestar oval shaped dish. I could only imagine that the offset angled feed would be a ***** to aim though. : ~
 
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K0ATC

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It would work well as the spec's are close. I have used my 1.5gig down to 900, though with degraded preformance it still did well. Just make sure on that amp, some of those power amps put juice down the coax can can hurt the front end of a receiver, but it seems you have been useing it for some time with success. I bought some amps that i was going to use as preamps for my ar5000 and turned out they were the type i am speaking of. Luckly someone said something prior to me useing them. I'm no expert with these thats why I like to have mine built by Down east microwave, they do a great job and they are not too expensive. The prime star is a great dish to use, but yes im sure it can be more difficult to aim. Let me know how it go's if you make your own. I am going to sell my expensive MTI gear and build my own for a fraction of the price, and have some money left over to play with.
 

mancow

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You know I never thought of the DC on the coax :eek:


I've used it on about every radio I own down to a GE RANGR and it didn't hurt anything so... but I will test it anyway.

Well... sounds like I need to go dig in the attic then.

The hard part is the physical construction. I wish I could find a simple design that's fairly foolproof. I'm afraid of dismantling everything and starting on this venture just to be left there with nothing coming from the radio and no damn idea in the world why. I found a helix progam that let me input details and get design ideas but I'm not sure what the ideal gain / bandwidth/ number of turns / etc... is.


Too bad it's not as simple as putting some mylar on the iside of an umbrella and turning it upside down. That would be a perfect portable setup. ( I assume that's a way farout idea) but I found an article where someone talked about it.

What I'm thinking about is a photographers silver mylar metallized umbrella.....?
 
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K0ATC

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Thats why i use an MTI dish, check it out in the photos sections of the yahoo group SCPC-FDM. This is a good group to be a part of.
 
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