hmm i wonder what killed it now i have no lock?..
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OK ā¦ This is the output of a spectrum analyzer (SA) connected to a Ku-Band satellite receiver in Los Angeles, CA. You are looking at a graph of Frequency (GHz) vs received signal (dBm). On the horizontal axis, the center frequency is set to 11,902 MHz, and the span is set to 10 MHz. So the plot is from 11,897 to 11,907 MHz. On the vertical axis is the relative signals strength into their SA. They have a large dish so that their noise/measurement floor is at -78dBm and the peak signal from Outernet is around -66dBm.
I have posted a similar plot when we first got our DC 3.02Q boards and the new Ku band frequency was announced. It can be used as a reference to figure out where the problem in the system is.
@clavo does this help? I can overload you with more detail if you want it.
āKonrad, WA4OSH
Use can you this nice profession system to āproveā that the skew between vertical and horizontal polarization make a difference. It is ease to toggle the button on the the receiver system and show that the signal virtually disappears when the āwrongā polarization is selected. I usually click the min hold button and watch for 10 or 15 minutes before I get excited.
Many people confuse that a ālinearā antenna can receive a ācircularā polarization system and exhibit only a 3 dB reduction. And that atmosphericās can distort the pure signal to quote āmuddy the watersā of a clean signal.
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Yes, excellent point! The satellite broadcasts two signals on the same frequency with different polarization - vertical and horizontal. If your skew is 90 degrees off, you will be listening to the other polarization on the same transponder. To see the signal on the other polarization, simply click on Horizontal instead of Vertical.
āKonrad, WA4OSH
@Syed Found it! Here is a SatSignature that I took on March 5, 2018:
Itās interesting to note that the Outernet signal appears to have grown wider and the peak power is lower. The noise floor is still the same. Note the peak power was at -61 dBm then. Also note thereās a new carrier slightly to the left (lower in frequency). Was there a change?
āKonrad, WA4OSH
Wider signal for more bandwidth?
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Wider could be for a higher data rate. It can also be for more spread factor, more process gain. Itās hard to tell without actually seeing the LoRa signal.
āKonrad, WA4OSH
SatSignature at May 17, 2018 at 7:30 PDT
Iām not sure whatās going on with the signal.
āKonrad, WA4OSH
Itās possible that you captured a time when we were testing at 800 kHz.
Wider does not actually mean higher data rate. The same amount of power is being spread across that wider bandwidth, which means that the energy per bit remains unchanged. Now in practice there are minor gains that come from tweaking nobs and switches. but itās definitely not a linear up-and-right bitrate increase when making the carrier wider.
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800 KHz back on March 5. I buy that. I of course donāt have access to your logs.
Your signal today looks like what I expected a 1.6 MHz signal to look like.
āKonrad
Yes, of course, it depends on what you are doing with the bandwidth - more symbols / higher data rate, more FEC, more spreading factor ā¦ etc. Makes total sense.
āKonrad, WA4OSH
Odd. Iām not even showing on the map anymoreā¦ and Iām still locked at -10-ish
I should be just S of the Seattle downlinkā¦
-liam
I see you - - 0700 EDT Friday 18 May - - right below Konrad. Ken
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Yup. Iām going to have to mess with it. Maybe some dog bumped into my tripod.
Iām still considering how to adapt my Wineguard MP1 for Outernet.
Iām also considering a more permanent dish installation on a 1 1/2 inch conduit pipe. I will mount the LNB on the vertical conduit pipe with a bracket salvaged from an old dish assembly.
Iām debating on where to mount my 2ft dish ā at my North Bend QTH or next to my YLās house in Bellevue. I definitely would love to run these remotely over the Internet.
āKonrad, WA4OSH
