Help Identifying Transponder Numbers and Transmit Frequencies on Spectrum Analyzer

rawbythesheeth

Member
Original poster
Nov 7, 2023
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1
Auburn, AL
I'm doing a school project that considers the path and frequency dependence of signal fading on satellite links, and I was wondering if I could get some help identifying the operating frequencies and orbital positions of the signals I'm seeing, or just some guidance as to where I can identify the transponders I'm looking at.

Here are screenshots from a spectrum analyzer of signals pulled off of a multiswitch. Signals are received by an SL3 (non-SWiM) LNB and the signals are separated using a bias tee placed between the multiswitch and the LNB. I have downloaded some of the documentation from the 'Directv Transponder Map Data' thread, but I haven't been able to piece the information together yet.

18V, 22KHz OFF:
99b Ka-Low, 101 Ku, 99a Ka-High
18V-22KHzOFF.PNG


18V, 22kHz ON:
103b Ka-Low, 110/119 Ku, 103a Ka-high
18V-22KHzON.PNG


I am confused by the 20MS/s signals in the Ku band slots on the 103/110/119 outputs. My understanding is that satellites 110/119 shouldn't be received by the SL3, and 110 isn't transmitting anymore. If that's the case, where are the signals coming from? I'm assuming these 20MS/s signals are Ku and transmitted from 103, but I'm unaware of what the Ku transponders could be. I checked in the 'DirecTV Domestic Bands Plans 210724' document, but the only Ku stuff I see there is for 101 and 119. Could these signals be the 'D15 Ku Band for use at 101W' listed in the 'Domestic Satellite Transponders 220519' document? I am aware that there is a Ku footprint map for D15 Ku-US at 103 in the 'Interactive Beam Footprint Library' thread.

How can I piece together the transponders/frequencies for all of these signals? I was previously consulting this diagram from Solid Signal Blog and information on LyngSat, but I've gotten a bit confused as of late.
bands-and-tone.png


Another thing worth mentioning - I noticed today the multiswitch is not outputting the 13V signal. I am okay with only looking at the LHCP signals, but I am unsure if this would affect the 18V lines' signals.
 
From my end, it looks like the pictures I attached are unavailable. If so, here they are again.
 

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A couple of things are going on here. First, Dish Nework has licenses for 110 and 119, for the transponder slots that DirecTV is not licensed for. So they will appear on your spectrum analyzer. The chart you have is a good one for any DirecTV Legacy LNB, or a SL5 or SL3, but I believe the SL3 designation was used for a LNB that only received KU band signals from 101 110, and 119, before HD. On first glance, those do not look like SL3 spectra, but I need more time to sanalyze what I am seeing. I am a E.E. and have used spectrum analyzers, but not for Satellite signals. *I've been retired for a while. If you can look at the label on the LNB, and get the model number, it would help. A Legacy SL5 only has 3 "eyes" the center one picks up 99,101, and 103 on 3 feedhorns inside the center.
 
Here is a picture of my Legacy SL5 LNB. The model number is below the rightmost "eye" (99/101/103) in this picture. A SL3 that did not get 110 and 119 would only have that eye, not the two offset ones. Some LNB manufacturers did not use the 3 bubble cover, and had a flat plastic cover.
 

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If you only provide 18V to the LNB, you will only get the LHCP transponders. There is no interaction. There is an internal multiswitch within the LNB, and each output is independent of the other. Each output can accept Any of the 4 combinations of tone and voltage. (Lines 5 and 6 of that chart for the Reverse Band are not of concern here.
 
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Looking at the graph for 18V, tone on, You are seeing all 16 transponder LHCP frequencies in the North American DBS Band plan. You are getting the 16 licensed to DirecTV and Dish at 119, superimposed with offset ones from Dish at 110. (TPN 28 from 110 is on the IF frequency of TPN 8 of 119). The LNB must have Band stop filters to keep the DISH transponders from interfering with the DirecTV transponders as they are mixed. Thank you for the spectrum analysis. I need to use my Genpix receiver and TSReader to figure which signal is DirecTV and which is DISH, when I have time.
 
Tom, thanks for the response!

My LNB:
SN: SL3K4NR0-02
1699564693761.png

Here's a picture I took back when I was installing.

I had concluded that the 12 upper and 12 lower signals were HD at 30 MS/s and the 16 middle signals were 20 MS/s SD, but they appear narrower due to the RRC pulse shaping.

The spacing between channel centers is approximately 40MHz for the Ka channels and 29.15 MHz for the Ku channels.

I was under the impression that I wouldn't be able to see the 119 satellites at all with this LNB.
 
You shouldn't be seeing 119 or 110 with that SL3 LNB. I have never looked at the signals from one of those. The two spectra look absolutely identical for the Ku band. Since it cannot switch to anything in the Ku band based on the tone, it looks like the internal multiswitch is just leaving 101 on those IF frequencies.
 
The signal being from 101 definitely seems the most likely. Thanks for your help. Glad there weren't any secret 103 Ku signals lurking about that I'd completely missed in my prep work.

The antenna is on a roof that I likely won't have access to before next week, but I'll try obstructing the 101 direction the next chance I get to see if the Ku signals attenuate on both cables.
 
This may help you correlate the TPN numbers to the frequencies on the coax (IF frequencies). Net 0 is 101W, 10 and 11 are on 99W, 14 and 15 are on 103. As for the others, Net 1 was 95W, 2 was 110W, 3 is 119, 12 and 13 are Reverse Band.
 

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The signal being from 101 definitely seems the most likely. Thanks for your help. Glad there weren't any secret 103 Ku signals lurking about that I'd completely missed in my prep work.

The antenna is on a roof that I likely won't have access to before next week, but I'll try obstructing the 101 direction the next chance I get to see if the Ku signals attenuate on both cables.
Did you reboot the receiver/dvr after you installed the lnb? I had the same thing happen until I did the reboot. Then 110 and 119 went away.
 
Could be, but IIRC, I was still seeing the 119 numbers, not 101, until I rebooted the dvr.
You are comparing apples and oranges. The issue here is what the LNB does with certain combinations of tones and voltage. You are talking about what the DirecTV STB displays before and after It initializes with a different LNB on the dish. The type of LNB and what it can tune to is only set in the STB at bootup, or after running Satellite Dish Setup in Settings. In this case there is no DirecTV STB involved. The internal multiswitch in a SL3 can't switch the Ku band on the coax between the 101 mixer and 110/119 mixer based on the tone, because there is no 110/119 mixer in the LNB.
 
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Could be, but IIRC, I was still seeing the 119 numbers, not 101, until I rebooted the dvr.

Without a connection to a working LNB it can't do any sort of autoconfiguration to figure out it is an SL3, or download the NIT from the satellite.

It probably uses some old copy from a dark corner of the firmware that hasn't been updated in a decade and that's why you saw 110/119.