Hi Tim,
what are the dimensions of your dish and what do you measure for distance to focus (that is from the lower edge of the dish) ? Have you tried the Octagon yet ?
One thing to be careful, is to look at the traffic on the transponder when checking the Beacon MER. Lots of carriers present can reduce the Beacon MER. Also weather. Yesterday, I'm sure I could detect heavy rain clouds passing by seeing fractions of a dB dip in the Beacon MER.
Below is an image from yesterday morning using my 1.2m, MER 9.8dB, D7. The Rx software was v0.9 beta 8_9. The decimal point MER value and 'D' value were only present when using my Serit (Mk 2) Minitiouner, not on my Sharp (Mk 1) type.
73
Jen
MER and D for es'Hail beacon ?
Re: MER and D for es'Hail beacon ?
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- Beacon 20190505.png (566.68 KiB) Viewed 4612 times
Re: MER and D for es'Hail beacon ?
Strange.. even with 0.9 beta8, I get consistent 7.5dB MER on my 88cm dish. But with a non-ruined LNB and no S-Band disturbing the dish pattern.g8gtz wrote: ↑Sat May 04, 2019 8:55 amHi Tim,
I did think your 9 was unusual on a 1.2mt dish - there's a table at the bottom of this wiki page which seems pretty consisent with what people are seeing: https://wiki.batc.org.uk/Receiving_Osca ... TV_signals
MER.jpg
Also we think the GH dish has moved and is down by a couple of dB but also Phil can adjust the gain remotely to try and keep it looking about right. 500 mile round trip to tweak the dish is planned at the end of May
And for the record on my 1.2mt Channel Master I used to get 7.5 > 8 with an unmodified dual octagon through an MJW patch. With the modified dish arms I now get a consistent 8.5dB.
73
Noel
Re: MER and D for es'Hail beacon ?
Hi Jen,
my dish is a CM 1.2M meaning it is 1.2M wide and 1.3M high.
I set the tip of the lens at 814mm from the dish as per the attached diagram. Looking down the 22mm pipe I could see the 'dot' on the dish at 791mm down from the top.
So unless I've got the wrong dimensions I think I've got the LNB positioned on the nose.
I did try an Octagon quad but found I only got and MER of 4dB ! despite tweaking the dish.
The octagon was a slightly looser fit inside the 22mm pipe compared to the AB which is a nice snug fit.
So I tried to shim the octagon unit with some copper tape but no improvement and switched back to the AB unit.
I did all these tests when the satellite was quiet as I had noticed the impact of other stations on the beacon strength.
I also checked the 'radome' was having no effect.
Would really like another dB, but might not be possible with the dual feed in place.
DH2VA - maybe you're a bit further South than us and so get a stronger signal ?
my dish is a CM 1.2M meaning it is 1.2M wide and 1.3M high.
I set the tip of the lens at 814mm from the dish as per the attached diagram. Looking down the 22mm pipe I could see the 'dot' on the dish at 791mm down from the top.
So unless I've got the wrong dimensions I think I've got the LNB positioned on the nose.
I did try an Octagon quad but found I only got and MER of 4dB ! despite tweaking the dish.
The octagon was a slightly looser fit inside the 22mm pipe compared to the AB which is a nice snug fit.
So I tried to shim the octagon unit with some copper tape but no improvement and switched back to the AB unit.
I did all these tests when the satellite was quiet as I had noticed the impact of other stations on the beacon strength.
I also checked the 'radome' was having no effect.
Would really like another dB, but might not be possible with the dual feed in place.
DH2VA - maybe you're a bit further South than us and so get a stronger signal ?
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- IMG-0319.JPG (1.72 MiB) Viewed 4564 times
Re: MER and D for es'Hail beacon ?
Hi Tim,
can't see anything wrong with the dimensions. Interesting to see that the Octagon was worse than the AB. From tests that I mentioned on the thread 'Which rocket Lens', I saw that the AB doesn't appear to suffer the LNB gain loss that the Octagon does around the beacon frequency, when considering the IF output frequency. The LNB gain is important to overcome the effect of down-stream thermal noise contributions arising from the receiver and cable loss and a lower MER in one case (lower gain) may indicate a rise in these.
I assume that you have a significant length of cable between the dish and Rx. I recommend to check that this has not become lossy or plug loose, especially as it's been on/off a few times with testing. Have you tried tried connecting your Rx at the dish with a few metres of known good cable ?
An aside on the AB LNB 01M. I noticed on the 'Octagon or Red Rocket' thread that G8VPG had taken a Red Rocket apart (see photos there) and the insides look identical to the AB LNB as shown in my earlier photos; looks like essentially they are the same device and probably the lens too.
Good luck and keep testing, its probably something simple !
73
Jen
can't see anything wrong with the dimensions. Interesting to see that the Octagon was worse than the AB. From tests that I mentioned on the thread 'Which rocket Lens', I saw that the AB doesn't appear to suffer the LNB gain loss that the Octagon does around the beacon frequency, when considering the IF output frequency. The LNB gain is important to overcome the effect of down-stream thermal noise contributions arising from the receiver and cable loss and a lower MER in one case (lower gain) may indicate a rise in these.
I assume that you have a significant length of cable between the dish and Rx. I recommend to check that this has not become lossy or plug loose, especially as it's been on/off a few times with testing. Have you tried tried connecting your Rx at the dish with a few metres of known good cable ?
An aside on the AB LNB 01M. I noticed on the 'Octagon or Red Rocket' thread that G8VPG had taken a Red Rocket apart (see photos there) and the insides look identical to the AB LNB as shown in my earlier photos; looks like essentially they are the same device and probably the lens too.
Good luck and keep testing, its probably something simple !
73
Jen
Re: MER and D for es'Hail beacon ?
Hi All,
Please do not get fixated on the highest possible MER. It is only relevant, unless really bad, for higher order modulation schemes. The decode quality is a combination of carrier to nose and carrier to phase noise. Our ability to decode weak signals will be limited mainly by the power rather than the phase noise in most cases. My Octagon quad gives 8.5 dB MER on the beacon and is phase noise limited, yet I can still decode 32 APSK at 33Ks if the signal is strong enough. Mostly with the locked PLL LNBs the far out phase noise is the problem, so wideband signals suffer more.
Mike
Please do not get fixated on the highest possible MER. It is only relevant, unless really bad, for higher order modulation schemes. The decode quality is a combination of carrier to nose and carrier to phase noise. Our ability to decode weak signals will be limited mainly by the power rather than the phase noise in most cases. My Octagon quad gives 8.5 dB MER on the beacon and is phase noise limited, yet I can still decode 32 APSK at 33Ks if the signal is strong enough. Mostly with the locked PLL LNBs the far out phase noise is the problem, so wideband signals suffer more.
Mike
Re: MER and D for es'Hail beacon ?
Hi Mike,
thanks for the reality check ! Yes all understand about MER and phase noise etc.
It's the old problem of what is good enough. Comparing my reception successes in terms of MER and D etc to that of others with seems to indicate I'm not too far behind the curve.
Regards Tim
thanks for the reality check ! Yes all understand about MER and phase noise etc.
It's the old problem of what is good enough. Comparing my reception successes in terms of MER and D etc to that of others with seems to indicate I'm not too far behind the curve.
Regards Tim