Signal variations on low elevation sats

[Captain Jack]

I've had this problem for a while - ever since I've had a clear eastern view.

This seems to happen on 66E and 68.5E, athough there's a less pronounced variation on 57E and 62E. What happens on 66E is that the signal on Mir stations seems to vary wildly from full lock with a solid picture and up to 52% SNR (on Uno) down to 0% in space of a few seconds. It needs around 45% SNR on this to be watchable on this TP.

Same thing happens on 68.5E, an overall stronger satellite. For example, on RTM (12722V), the max signal strength goes up to about 63% but it jumps up and down constantly! At one point it dropped to 30% and the picture broke up. It's not windy and the dish is stable on its mounting. What could be the cause of this? Earth radiation because of low elevation?

TPs on 57E like Duhok TV and Aden Live on 62E take forever to lock and drift in and out constantly. Although, I think these are weak signals with a low SR, which the Uno struggles with.

I don't see this on any other satellite and there's no such variation on the nearest low satellite 53E.

Any ideas?

 

[Channel Hopper]

The amount of atmosphere the signal has to travel at low elevations increases dramatically towards the horizon. Any change in particle density along the route makes a difference in the signal received, especially at Ku band.

Contaminants and even air temperature from thermals will throw all sorts of different stuff into the path.

 

[Captain Jack]

Indeed. Looks like there's nothing that can really be done about this then, other than move!

 

[nelson_b]

hi -
i had 80 c.m. a fixed dish setup on 68.5 east a couple of years ago -- (elevation is 2.4 for that sat from here ) --
it always suffered from signal fluctuation even in good weather - and in and out of lock in bad weather ,
it was the same for another enthusiast who lived only 25 miles from me using a 100 cm dish.

like you - 53 east is stable enough -- a lot more elevation on this one though --

regards --- nelson.b.

 

[Captain Jack]

...which makes this hobby all the more fun!

Waiting for Intelsat 22 @ 72E to light up so I can see what it's like here at 0.7 degree elevation!

 

[timo_w2s]

...which makes this hobby all the more fun!

Waiting for Intelsat 22 @ 72E to light up so I can see what it's like here at 0.7 degree elevation!

Funnily enough I was just looking at dishpointer earlier on today and noticed that 47°W is right on the horizon in Helsinki. Intelsat 14 at 45°W is 1° above the horizon and since I have a west facing balcony 80m in the air there's a good chance I can physically see this satellite. The problem is I can't get anything bigger than an 80cm dish up there and the 47dBW power level will no doubt be a bit weak under those conditions for an SCPC channel to get a lock but I might give it a go next time I'm over there for fun. (Assuming something is broadcasting from there to Europe? 11607/H RASD TV?) Pretty sure I won't get anything though.

 

[Captain Jack]

Rasd tv was still there last time I looked a couple of months ago.