FW: [SatSignal] data loss

Robert Moore

-----Original Message-----
From: SatSignal@groups.io <SatSignal@groups.io> On Behalf Of David J Taylor GM8ARV ?????????????? ???? via groups.io
Sent: 09 May 2022 19:06
To: SatSignal@groups.io
Subject: Re: [SatSignal] data loss

On 09/05/2022 15:51, Robert Moore wrote:
The engineer is coming soon for his last attempt to restore full reception. He intends to fit a new LNB (to replace the new one I bought!). My current situation is as follows: Basic reception yesterday, 479 HRIT images received and as far as I can see from a quick inspection very few of them are incomplete. But I reckon with 12 channels, four times an hour, there should have been 1,152 images. Metop-C nothing yesterday, today very little, just a few images around each pole. Metop-B, images coming in rather randomly (ie jumping around geographically) and leaving big gaps.
This next visit will be my last chance with the engineer – he doesn’t really know what to do next. I just hope the new LNB might work a miracle. All other suggestions (other than moving house) most welcome.
I'm at a loss as to what to suggest, Robert.

If the engineer has a meter, what SNR does he see? I would hope for at least
12.0 dB. Is it different between his reading at the antenna and your reading from your receiver? That would be a simple cable check.

Is there any chance your dish has been bent out of shape? At 10 GHz the wavelength is just 30 mm, so a quarter-wavelength deviation would be just 7 mm
- about a quarter of an inch.

The other issue might be where the disk is mounted. Ideally the LNB should "see" just the dish, but in reality there will be overspill of the LNB "view"
beyond the edges of the dish. If that is warm brick of ground - anything other than sky - it will have a much higher radio temperature than sky, and this can cause loss of SNR.

Perhaps ask in the MSG-1 group too?

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