OTHER Why Are SR Numbers Off?

[Lone Gunman]

Got a question about the SR numbers on one of my systems.

Example:

I just finished doing a rescan of 107w with both my Winegard and Raydx systems using 2 different Micro HD receivers. Raydx has a DMX741 LNBF with the old style metal cap on the Ku end and the Winegard has a newer WSI NS741 LNBF.

What's happening is on “some” of the SR numbers, especially those up in the high ranges on the Winegard system will be about 125 off, ie, Raydx scans it in at 30000 and the Winegard scans it in at 30123?? I can go in and Edit the Winegard number down to 30000 and it will still lock it at the same Q as before and it seems to work fine like that?? Question though is, why is it doing that?

Oh, and FYI, if I put that receiver on the Raydx system it scans the SR at 30000 so it's something caused by that LNBF on the Winegard system??

I realize that it's “normal” for scans to be a few numbers off up or down but 123 just seems to be way too much.

Any idea what's going on with this?

 

[waylew]

Oscillator in the LNBF likely starting to drift off frequency.

 

[Lone Gunman]

Oh, and it doesn't do that on all SRs either. Some will scan in at 29998, some at 30000 and some at 30125 or so?

EDIT: Just had one SR on 103w that was 29875 on the Winegard and 30000 on the Raydx so it looks like it goes both ways??

 

[Titanium]

Symbol Rate parameters have nothing to do with the LNB LO frequency accuracy. The logged SR is an estimation (calculation) during the receiver's blind scan process based on the bandwidth and FEC. That MHD's 125 SR miscalculation was odd and something that I wanted to resolve, but never made it to the top of the priority list.

 

[Lone Gunman]

Symbol Rate parameters have nothing to do with the LNB LO frequency accuracy. The logged SR is an estimation (calculation) during the receiver's blind scan process based on the bandwidth and FEC. That MHD's 125 SR miscalculation was odd and something that I wanted to resolve, but never made it to the top of the priority list.

So, are you saying this is a known defect in the MHD then? IIRC this one is the only one of the three that I own that does this so I was thinking it was the LNBF on that Winegard system?

 

[Titanium]

It was a noted issue for the chipset SOC and was present on several platforms utilizing earlier ALI chipset versions. Since it did not affect reception and would randomly appear while blind scanning SR 30000 transponders, the ALI
SOC engineering group had responded with programming recommendations that would have ultimately impacted the overall blind scan performance. Haven't observed the issue in later ALI chipsets.