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Guest Message by DevFuse

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Any ideas on this installation error message?


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33 replies to this topic

#21 ONLINE   veryoldschool

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Posted 05 May 2012 - 08:06 AM

But the IV retest is performed at the receiver, is it not?

While I can understand how the actual RF signal levels can be seen by the receivers in legacy installs, for SWiM unless the IV retest is about detecting if RF levels fall below the agc range of the SWiM, I don't see how the receiver can see any other than the C/N ratio (sensed as BER of course) to use for the test. :confused:

The RF signal power at the receiver input once regulated by the agc action of the SWiM is a nominally constant -30 dbm minus any intervening coax and splitter losses isn't it?

I know someone with a new AIM coming, and this sounds like some good things to look into.
If the Ka levels are low to the SWiM, it can't do anything more than add its 15 dB of gain, and if this is less than the Ku levels, "it might" trigger the errors seen in the first post.
A.K.A VOS

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#22 OFFLINE   HoTat2

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Posted 05 May 2012 - 09:26 AM

I know someone with a new AIM coming, and this sounds like some good things to look into.
If the Ka levels are low to the SWiM, it can't do anything more than add its 15 dB of gain, and if this is less than the Ku levels, "it might" trigger the errors seen in the first post.


OK, though to be honest VOS, even when measuring at the dish with a signal meter I've always been a bit fuzzy on understanding peaking with a SWM LMB. Once the RF satellite signal level to its integrated SWM reaches around -45 dbm or above, won't the SWM's agc circuit mask any further signal variations?

All the signal meter is going to get at that point is a constant (nom.) -30 dbm from the LNB correct?

Even dithering seems a little weird since it would seemingly need to be done over a "flattened" peak due to agc action as I remember you once pointed out.

#23 ONLINE   veryoldschool

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Posted 05 May 2012 - 09:59 AM

OK, though to be honest VOS, even when measuring at the dish with a signal meter I've always been a bit fuzzy on understanding peaking with a SWM LMB. Once the RF satellite signal level to its integrated SWM reaches around -45 dbm or above, won't the SWM's agc circuit mask any further signal variations?

All the signal meter is going to get at that point is a constant (nom.) -30 dbm from the LNB correct?

Even dithering seems a little weird since it would seemingly need to be done over a "flattened" peak due to agc action as I remember you once pointed out.

There's a lot that needs to be looked into in more detail.
Yes the AGC does "mask" the output, but the Birdog can't measure the SWiM output, so the AIM will be needed.
The legacy LNB loses lock at in the -39dBm to-40 dBm range as seen here:

http://www.dbstalk.c...=1&d=1336233190

Hopefully soon there will be some more testing using the AIM, as the IV test may use tps that are known to be lower than others, so the LNB can be locked [due to the higher tps].

Another thing to look at is how the SWiM AGC functions.
Does it adjust each channel, or "merely" the whole output as one?

Attached Thumbnails

  • LNB output.png

A.K.A VOS

#24 OFFLINE   HoTat2

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Posted 05 May 2012 - 11:30 AM

Yeah, as I said I can readily grasp the concept for measuring signal levels on a legacy LNB like that, but its the SWM type that's still got me somewhat confused. If I'm properly understanding how the agc circuitry functions for the SWM LNB you wouldn't even be able to see a -38.8 dbm signal level like in that example since the agc circuit would amplify it by ~9 db for its usual limit of -30 dbm nominal output.

Be interesting to see how the AIM meter is able to somehow "see through" the masking effects of the agc to derive the actual RF power levels on the input side of the integrated SWM.

BTW: What's the prominently displayed "-43.4 dbm" level at the bottom center of the meter screen mean?

#25 OFFLINE   RobertE

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Posted 05 May 2012 - 11:42 AM

The AIM meter puts the LNB into a "aiming mode". ;)
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#26 ONLINE   veryoldschool

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Posted 05 May 2012 - 11:50 AM

Yeah, as I said I can readily grasp the concept for measuring signal levels on a legacy LNB like that, but its the SWM type that's still got me somewhat confused. If I'm properly understanding how the agc circuitry functions for the SWM LNB you wouldn't even be able to see a -38.8 dbm signal level like in that example since the agc circuit would amplify it by ~9 db for its usual limit of -30 dbm nominal output.

Be interesting to see how the AIM meter is able to somehow "see through" the masking effects of the agc to derive the actual RF power levels on the input side of the integrated SWM.

BTW: What's the prominently displayed "-43.4 dbm" level at the bottom center of the meter screen mean?

It wasn't in my hands, but would think it was the current level being measured at the time of the photo, with the bar being the peak that is displayed, like shown here:

http://www.dbstalk.c...=1&d=1336240135

Maybe by the end of next week I can have some of the data/testing done by who's getting their AIM.

Attached Thumbnails

  • LNB1 output.png

A.K.A VOS

#27 ONLINE   veryoldschool

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Posted 05 May 2012 - 11:58 AM

The AIM meter puts the LNB into a "aiming mode". ;)

Would you care to offer your opinion on the differences between using a Birdog and the AIM?
A.K.A VOS

#28 OFFLINE   HoTat2

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Posted 05 May 2012 - 12:53 PM

The AIM meter puts the LNB into a "aiming mode". ;)


And sorry for being dense, but your "wink" emoticon makes me ask. Are you serious?

There really is such a thing as "aiming mode" for the SWM LNBs which the AIM meter activates to which I assume removes the agc circuit from the mix for dish alignment?

#29 OFFLINE   RobertE

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Posted 05 May 2012 - 06:42 PM

And sorry for being dense, but your "wink" emoticon makes me ask. Are you serious?

There really is such a thing as "aiming mode" for the SWM LNBs which the AIM meter activates to which I assume removes the agc circuit from the mix for dish alignment?


Yes. When power is applied to a SWiM lnb without any irds present, the lnb goes into aiming mode. Basicly, as you guessed, with the AGC disabled. The aim meter will also force it into that mode as well.
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#30 OFFLINE   RobertE

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Posted 05 May 2012 - 06:46 PM

Would you care to offer your opinion on the differences between using a Birdog and the AIM?


Last I knew, none of the birdogs would "lock" onto 99/103, and only the latest model would power it by itself. The aim did both, in addition to allowing you to look at individual transponder levels. You can also check to see if you are meeting the threshold to pass the IV test as well while still at the dish. That helps determine if cable quality/length, splitters, connectors, etc may be part of any signal issues. Its a very nice meter purpose built for the job.
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#31 OFFLINE   ndole

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Posted 05 May 2012 - 09:51 PM

Last I knew, none of the birdogs would "lock" onto 99/103, and only the latest model would power it by itself. The aim did both, in addition to allowing you to look at individual transponder levels. You can also check to see if you are meeting the threshold to pass the IV test as well while still at the dish. That helps determine if cable quality/length, splitters, connectors, etc may be part of any signal issues. Its a very nice meter purpose built for the job.


It also gives you SWiM CH assignments by RID, actual power levels, CNR, and in line voltage tests while under current load. The newest release has guided testing also.

I'm looking forward to the future of the AIM. It's firmware base is being upgraded all the time, and I'll be happy when there are some more SWiM specific diagnostic tools available.
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#32 OFFLINE   dielray

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Posted 06 May 2012 - 05:54 AM

IV and IV Retest use only the receiver's "percentage" numbers. The minimum levels vary by zip code. The levels seem to be built into the IRDs, as forcing a download seems to change the values enforced. Recently, they seem to check more transponders, but require lower values.

IV via the AIM measures SNR, LNB offset, and power level.

The SWM LNB can be placed in peaking mode by having no receivers connected.

In my area in peaking mode, the top dBm value of the 101 seems to be about -22. On a legacy LNB it is about -30. We use WNC LNBs in both cases.

Not sure how to check how the AGC works. The sat tune function of the AIM is affected by the AGC. 101 Tx25 has a lower power level in sat tune than it has when using the install function.
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#33 OFFLINE   HoTat2

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Posted 06 May 2012 - 09:11 AM

IV and IV Retest use only the receiver's "percentage" numbers. The minimum levels vary by zip code. The levels seem to be built into the IRDs, as forcing a download seems to change the values enforced. Recently, they seem to check more transponders, but require lower values. ...


Thanks for the info, and is what I suspected as to why my ... well lets just say "less than stellar" :) Ka band signal levels here in South L.A. still manage to always pass an IV retest.

In fact in a related issue once during a D* tech. training video I watched about the ISS department, one of their main complaints of the IV retest procedure was when a sub. moves from an area of the country with higher level signal requirements to that of a lower one and they fail to get notification from D* of the address change for that sub.'s account in their system. Therefore during any service call to that sub. that mandates an IV retest as a part of it, the test then keeps failing no matter what the tech. does. The tech. then regularly calls ISS out of frustration where they have to sort it out.

... IV via the AIM measures SNR, LNB offset, and power level.


LNB offset?

Now I know this can't be referring to the LNB offset angle of the dish the AIM is measuring :sure: So what's this a measure of, the LNB's L.O. frequency error or something?

... The SWM LNB can be placed in peaking mode by having no receivers connected.

In my area in peaking mode, the top dBm value of the 101 seems to be about -22. On a legacy LNB it is about -30. We use WNC LNBs in both cases.


OK great, this and the info. from Robert E earlier really clarifies how the SWM LNBs are peaked. And I guess this is the reason a "flattened" peak response curve theorized a while back by VOS which indeed should exist if the agc circuit is active was strangely never reported by the installers when peaking the dish.

#34 OFFLINE   ndole

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Posted 06 May 2012 - 09:29 AM

LNB offset?

Now I know this can't be referring to the LNB offset angle of the dish the AIM is measuring :sure: So what's this a measure of, the LNB's L.O. frequency error or something?


It's a measure of how far off the received down link frequencies are from where they should be. IIRC, it could be an error in the precise measures of the wave guides or of the down conversion circuitry.
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