Inmarsat Reception - Patch Antenna and Line of Sight

[KC1UA]

Good morning,

I'm wondering if anyone is using this antenna for Inmarsat reception:

PREORDER SALE: Active L-Band 1525-1637 Inmarsat to Iridium Patch Antenna Set For $34.95

Over the last several months we've been working on a versatile active L-band patch antenna that can cover Inmarsat to Iridium satellite frequencies. That antenna is now almost ready, and should be able to ship out from our Chinese storage warehouse by week 1 or 2 of October NOTE: Due to an...

www.rtl-sdr.com

Seems like an inexpensive fun way to try things out. I am concerned about line of sight as I have a lot of trees. I'm assuming from my location (Cape Cod MA USA) I'd be looking at the 54 degrees west satellite which could be problematic. Is an entirely unobstructed view of the sky necessary for success? I'm guessing so but new at this aspect of monitoring. I used to install C band (4 GHz) satellite dishes in another lifetime and without a doubt no obstructions could be tolerated.

Thanks in advance.

 

[prcguy]

I have not used that antenna but it does look awfully small for the task. It appears to be a linear polarized antenna where most satellite downlinks are circular polarized. It worries me when they say you have to rotate the antenna for best reception.

 

[scudGB]

HI KC1UA
yes its good fun if into planes or marine as software for both free check my posts and see what is possible with home made antenna
what are the trees blocking your LOS ? we are running into winter in uk and no evergreens near my location so i will get fair signal for a few months
my sub post UPDATE ON HELICAL is actualy inside roof space with real slate tiles and a pretty large tree almost bald 30 ft away but you can see my signal in pic its not to bad
with your skill set try get a 1M offset dish of ebay and see if extra gain will offset loss from trees scud

 

[vagrant]

Yep, it is linear thus the rotating. A dish/reflector would help. Perhaps 1 - 2 meters in size. Anyone sell a portable parabolic dish solution that's 1-2 meters in size? I would rather try to RX some GEOS images around 1690, but this antenna does not appear to be a solution for that.

 

[NYG]

I have one of those antennas. I've only done minimal testing with it from the front porch of my house and it does indeed work. I started getting an interest again in Inmarsat but didn't feel like dealing with the dish I have. The dish gave me a stronger signal but i didn't really try to optimize the location of the little antenna. Signal was good enough to test some decoding.

Just for reference I'm on Long Island. You can buy on Amazon and return if you don't like it. It's not a rugged build or anything but certainly cheap enough and the portability is great if it works out for you. I was using it with the LimeSDR.

 

[royldean]

There are reports on the RTL-SDR.com blog that some people have had some success using this antenna indoors - so it should still be usable even with some foliage in your way. For what it costs, it seems like a no-brainer if for nothing else than experimentation.

 

[KC1UA]

Thanks for the responses. For the short $$ I'll likely give it a whirl. Can't hurt to try and as noted it can be returned.

 

[batdude]

I'm very new at the INMARSAT game, so bear with me.

I bought one of these $40 antennas the other day. it does work. i am still playing around with how to get the best signal from it --- currently i have it mounted on my old DirecTV dish in the back yard taped to where the DTV LNB is.... I have tried also just placing it on the dish itself and didn't see much difference in signal strength.



My setup comes into an Airspy running SDR# with Scytale-C Quick UI. There is a plug in for SDR# that sends the data to Scytale-C without fooling around with VB audio cables (link: https://bitbucket.org/scytalec/scytalec/downloads/ ). Seems to work great - and AUTO TUNES the signal. (obtw, most fail to mention this - but the "mode" you need to be in is USB, not NFM or AM - and i have my bandwidth set to ~4khz.

What you won't find (at least I have not yet) is a list of frequencies that you can decode / work.

Start here: 1537.700 GHz. This is the NCS channel for the AOR-W (western Atlantic) you will see the SafetyNet messages, etc. come via this freq. NOTE: it's slow. 600baud. This isn't T1 levels of data xfer.... you can tell that the signals you are after are REALLY weak... so quality coax and connectors (and short cable runs) are important. Every dB helps.

i don't think I have the knowledge to ask any questions yet.... but hopefully this helps.

 

[vagrant]

I bought one of these $40 antennas the other day. it does work. i am still playing around with how to get the best signal from it --- currently i have it mounted on my old DirecTV dish in the back yard taped to where the DTV LNB is.... I have tried also just placing it on the dish itself and didn't see much difference in signal strength.

Rotate the antenna you put on the LNB. Try it one way and then the other and watch it inbetween. You'll need to see your numbers as you turn it. The antenna is linear. Once you have the right twist, you can experiment with moving the antenna closer and further from the dish. You may need to play with the twist again too. Still, you're receiving signals now so if a rotation improves it, I may just leave it alone in that new position on the old LNB.

 

[prcguy]

I think one problem here is the focal point of the DirecTV dish is roughly at the circuit board inside the housing several inches back from where you mounted the L-band antenna. You would have to remove the DirecTV LNB and make a bracket for the new feed then find some way to optimize the focal point and adjust for best gain and minimum sidelobes. You will also have to rotate the feed as vagrant mentioned. When your all done you might get 15 to 17dB more gain if the pattern on the L-band antenna is ok with the offset dish.

Not that it matters or I know anything about this stuff, but my name is on 3 of the patents for the dish you are using.

I'm very new at the INMARSAT game, so bear with me.

I bought one of these $40 antennas the other day. it does work. i am still playing around with how to get the best signal from it --- currently i have it mounted on my old DirecTV dish in the back yard taped to where the DTV LNB is.... I have tried also just placing it on the dish itself and didn't see much difference in signal strength.

View attachment 77355

My setup comes into an Airspy running SDR# with Scytale-C Quick UI. There is a plug in for SDR# that sends the data to Scytale-C without fooling around with VB audio cables (link: https://bitbucket.org/scytalec/scytalec/downloads/ ). Seems to work great - and AUTO TUNES the signal. (obtw, most fail to mention this - but the "mode" you need to be in is USB, not NFM or AM - and i have my bandwidth set to ~4khz.

What you won't find (at least I have not yet) is a list of frequencies that you can decode / work.

Start here: 1537.700 GHz. This is the NCS channel for the AOR-W (western Atlantic) you will see the SafetyNet messages, etc. come via this freq. NOTE: it's slow. 600baud. This isn't T1 levels of data xfer.... you can tell that the signals you are after are REALLY weak... so quality coax and connectors (and short cable runs) are important. Every dB helps.

i don't think I have the knowledge to ask any questions yet.... but hopefully this helps.


View attachment 77354

 

[batdude]

but my name is on 3 of the patents for the dish you are using.

Fair enuf!

i will fart around with it tomorrow and update the thread. meanwhile, I will study antenna focal length calculations.

and drink heavily.



doug

 

[prcguy]

I'm not familiar with the latest DTV LNB but see if you can take it apart and remove the internal casting with circuit board inside leaving the back of the LNB housing and lever lock mount intact. I think if you could mount your new L-band antenna about even with the flat back of the DTV LNB it would be close and the lever lock thing might allow you to fine tune it a little.

Fair enuf!

i will fart around with it tomorrow and update the thread. meanwhile, I will study antenna focal length calculations.

and drink heavily.



doug

 

[royldean]

Not that it matters or I know anything about this stuff, but my name is on 3 of the patents for the dish you are using.

Pfft.... I got my name on some patents where my only involvement was sleeping in the back of the conference room when the idea was conceived.

 

[dlwtrunked]

I have not used that antenna but it does look awfully small for the task. It appears to be a linear polarized antenna where most satellite downlinks are circular polarized. It worries me when they say you have to rotate the antenna for best reception.

It is a common circularly polarized antenna design used by GPS and other antennas for other services in L-band. They said you may have to rotate it because they mean you may have to aim it properly. (As INMARSAT are geostationary that is not a big deal for them.) I have used cirularly polarized antennas of that size before for INMARSAT though I prefer my 1 meter dish.

 

[prcguy]

Congratulations, we are all so proud of your accomplishment.

?

I was quite awake and involved in my projects and completely dreamed up one of the inventions.

Pfft.... I got my name on some patents where my only involvement was sleeping in the back of the conference room when the idea was conceived.

 

[jlh]

For those of you who may not know, prcguy is the de facto satellite expert. I have taken his advice for years. If he says it, do it.

 

[royldean]

For those of you who may not know, prcguy is the de facto satellite expert. I have taken his advice for years. If he says it, do it.

And yet he can not detect "supportive joking" - too bad. Jeebus man, I "liked" his comment and my response is obviously in jest.

 

[hamradionl]

I just did some testing with AIRSPY-mini, but in my case this not working. AIRSPY-mini the lowest sample rate is 3 MSPS. My RTLSDR-3 or Nolec-4. go as low 0.25 MSPS and give much better error free voice and data

 

[rcpcaetano]

Hello, I live in Brazil and I use a 50cm satellite dish and an external GPS antenna, to receive the Inmarsat L-band satellite. I use the 54w, I have a very strong signal. I use sdr-console V3 and Sdrsharp software to decode scytale-c and winSTD-C standard Demo. Dongle: RTL-SDR V3. I see some signs of Aero and Ships, and some unidentifiable ones. 73 of PU1XTB.

 

[strandbiker1]

Does anyone have any experience in ScytaleC and the Quick UI interface? I am using SDR Sharp and a and a NooElec NESDR Smart tee and a SAWBird iO +. I did the update to SDR Sharp for the ScytaleC and downloaded the Quick UI, but how does it interface? Does it go in the SDR Sharp directory?

TIA

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