Very hot here in LA again. SNR keeps dropping? Rig is outside in sun. Put big 16" fan blowing on parts. See improvement in SNR by dB and a half in a few minutes. I think Outernet dongle needs heat sink strapped to both top and bottom as standard.
Interesting?
How hot is your Outernet e4000 dongle getting?
Are you sure it is heat reducing SNR rather than strong sun effecting the propgation of the L-Band signal.
I am finding RAIN clouds are having a BIG effect here in the Philippines on my SNR.
Inside and pointing through a window, dongle is just warm. But SNR a bit marginal, so took rig outside.
A couple of dB better, near 5+. But day got hotter, very bright Sun. SNR dropping. Dongle hot. Electric fan helped
a lot. You mentioned Sun affects propagation. Could you explain?
Many types of Attenuation of the L-Band 1.5ghz Signal can occur any where between the Inmarsat Satellite on the Geosynchronous Clarke Belt approx 36,000km away and your ground based Outernet L-Band antenna.
RainFade.
Rain fade can be caused by precipitation at the up-link or down-link location. I am not sure if the Inmarsat re-boosts the up-link signal that it then transfers to the down-link Outernet feed.
A low look angle for the antenna increases chance of rain fade.
Attenuation can be caused by Signal from the electromagnetic interference of the leading edge of a storm front.
During the Day the Sun can play a large part in Charging the Ionosphere.
“Among other atmospheric regions, ionosphere, which is ionized region of the atmosphere, is considered to impose serious limitations on satellite communication. At higher frequencies, radio waves pass through the ionosphere and are attenuated due to the free electrons present in
ionosphere.”
The way we deal with Fade or attenuation is hopefully have enough gain in our Antenna to overcome the most likely known attenuation’s that will happen.
In the best case scenario for the Outernet Lantern the small Aluminum L-Band antenna could possibly have a SNR of 8.
The Outernet Lantern hardware and software need a SNR of 2 in order to reliably decode data packets.
So the Outernet Lantern in ideal conditions has a Fade factor SNR of 8-2 = 6.
Hopefully 6 SNR Fade factor is enough to overcome any of the above attenuation issues.
Thanks Seasalt. I suspected a couple of points you mentioned. But you clarified nicely.
BTW I read the output RF power of many communication satellites is only about 67 watts. But the ERP
really much much higher due to the big dish on the bird. Maybe 40 dB of gain.
I4F1-APAC at 144E
Center frequency: 1545.9525 MHz
Channel bandwidth: 5 kHz
EIRP: 18 dBW
Polarization: RHCP
Coverage area: All of Asia from India eastward to Hawaii, including all parts of Oceania.
Launch date: 11-Mar-2005
Launch site: Cape Canaveral
Launch vehicle: Atlas 5 (Atlas V)
Launch mass (kg): 5959
Dry mass (kg): 3340
Manufacturer: EADS Astrium
Model (bus): Eurostar-3000GM
Orbit: GEO
Expected lifetime: 13 yrs.
Details:
228 Narrow Spots, 19 Wide Spots and 1 Global Beam to support the new Broadband Global Area Network (B-GAN) for internet and intranet solutions, video on demand, video-conferencing, fax, e-mail, telephone and high-speed LAN access
The Inmarat L-Band signal for each of the 3 Outernet beams is not a spot beam but a WIDE beam.
I make the following assumptions.
I think the signal is put out by one transmitter and one directional dish antenna.
Inmarsat transmits on one range of frequencies and receives on another higher or lower range of frequencies.
Traditionally the biggest problem with Satellites was the solar panels powering the Satellite limited the transmission power.
I am not so sure that is the case today. The 4F1 satellite is I think 13 years old and getting to end of Life.
The next generation of Inmarsat Satellites may not be so power limited and be able to put out a much stronger signal.
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Very good. I’m using 4-F3 for the Americas, Easy elevation, just under 45 degrees. About 146 degrees Azimuth from LA. I’m sure you know
about N2YO http://www.n2yo.com A pretty neat site.
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Hot Sun shinning on Outernet dongle definitely affects SNR. It happened again this afternoon. SNR came up almost 2 dB when fan was turned on right next to it. Probably 90 F or more at dongle location. Now I see SNR 4.96 with fan. Before, just barely over 2 without fan.