RTL-SDR for Iridium

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bgorr
Posts: 1
Joined: Sat Jul 25, 2020 6:19 am

RTL-SDR for Iridium

Post by bgorr » Sat Jul 25, 2020 6:24 am

Hello,

I am hitting a bit of a roadblock trying to receive Iridium signals with the RTL-SDR. I am using a NooElec LNA to amplify the signal, and am using a Taoglas antenna (https://cdn3.taoglas.com/datasheets/IAA.01.121111.pdf). I am not using the recommended 30x30cm copper mounting plate since my intuition is that it would improve performance but not be necessary. Would it be necessary? Are there any peculiarities to receiving the Iridium signal that I should be aware of? I would like to use the Iridium antenna sold by RTL-SDR but it is currently out of stock. Are there any cost-effective alternatives to receive the Iridium signal?

I would appreciate any guidance on the subject. Thanks in advance.

Ben Gorr

alanzfq
Posts: 160
Joined: Thu Oct 04, 2018 11:18 am

Re: RTL-SDR for Iridium

Post by alanzfq » Sat Jul 25, 2020 6:36 am

A plate is likely to improve reception particularly as it is specified as part of the antenna system.
It's dimensions are not likely to be too critical, just as big as possible. A car roof or anything like that?
Alan

Stromeko
Posts: 37
Joined: Wed May 01, 2019 6:32 pm

Re: RTL-SDR for Iridium

Post by Stromeko » Sat Jul 25, 2020 7:47 am

bgorr wrote:
Sat Jul 25, 2020 6:24 am
I am not using the recommended 30x30cm copper mounting plate since my intuition is that it would improve performance but not be necessary. Would it be necessary?
Intuition and RF don't mix well unless you are one of very few gifted individuals. If an antenna is designed to work with a ground plane and the manufacturer goes to the lengths to actually specify the dimensions you should at least start with that before you intuit otherwise. I have no experience with Iridium, but for GPS patch antennas the addition of a properly sized ground plane can improve SNR by almost 30dB. Depending on what the link SNR budget is that may very well be the difference between having none or good reception for Iridium. You may skimp a bit by using aluminum foil rather than a copper mounting plate, but no ground plane at all is not a good idea obviously.

alanzfq
Posts: 160
Joined: Thu Oct 04, 2018 11:18 am

Re: RTL-SDR for Iridium

Post by alanzfq » Sat Jul 25, 2020 8:38 am

Is this Iridium?
FCD and ordinary GPS antenna no plate.
Attachments
Iridium1621.790w.jpg
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alanzfq
Posts: 160
Joined: Thu Oct 04, 2018 11:18 am

Re: RTL-SDR for Iridium

Post by alanzfq » Mon Jul 27, 2020 7:40 am

I found not all GPS antennas pickup Iridium. A good one, far better SNR shown an a GPS program, did not pickup Iridium. It was far better for GPS satellites but must have had a good filter preventing out of band signal reception.
I also tried 3 RTLs and did not manage to receive anything. I guess the Iridium antenna might? Look around 1626.100 for the simplex channels, constant activity seen as the satellites pass over.
Alan

weathersatelite
Posts: 33
Joined: Tue Jan 14, 2020 4:34 am

Re: RTL-SDR for Iridium

Post by weathersatelite » Tue Jul 28, 2020 10:11 pm

its been said. yes the more expensi e ones have a good filter. there is a post on the main website. you have to remvoe it. the cheap anteans may not have a filter.
post an a similer sat here
https://www.rtl-sdr.com/rtl-sdr-tutoria ... -messages/

alanzfq
Posts: 160
Joined: Thu Oct 04, 2018 11:18 am

Re: RTL-SDR for Iridium

Post by alanzfq » Fri Jul 31, 2020 7:35 am

Thanks, until Ben asked I'd not thought of trying these little puck antennas for seeing satellites.
All my RTLs are old ones with an external bias T and so far I've not managed to use one successfully. The Funcube dongle and Pluto shows them, I've not tried any decoding software yet.
Alan

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