sat hero 44% versus zgemmah7 37%

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belter-one
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sat hero 44% versus zgemmah7 37%

Post by belter-one » Sun May 13, 2018 3:17 pm

Hello,

According to the SH-400-HD sat hero my 10 foot c band satellite is receiving a signal strength of:

* 44% for Galaxy 13's 3920V 28068 3/4 transponder for the three wonderful NASA channels.
* The ZGemma H7S receiver states the signal quality is 36 - 37%.

Does this indicate that the two different devices measure signal quality differently?
Does this indicate that the receiver is somehow dropping useful signal?
Could this indicate that I need to clean these connectors?

Any information would be very much appreciated. I am going out now to take measurements directly from the LNB, recheck the dish and its alignment.

A beautiful day,

belter-one

P.S. Love the imbedded Linux operating system on the ZGemma H7S.

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Re: sat hero 44% versus zgemmah7 37%

Post by fatso » Sun May 13, 2018 10:44 pm

The % SNR is relative and varies from receiver to receiver and meter to meter. I would switch to an absolute SNR in dBs. To do this in your zgemma, perform the following:

Menu - Setup - Usage & GUI - OSD Settings

Scroll down to Swap SNR in % with SNR in dB. Select yes.

Now your receiver will display SNR readings in dB which are easier to understand. For example, a DVB-S signal with FEC = 3/4 requires a minimum SNR of 5.5dB to be decoded by the receiver. A DVB-S2 signal with FEC = 5/6 requires a minimum SNR of 9.4 dB to be decoded. These are the main ones you should remember: DVB-S signals (standard definition channels) will usually decode if SNR > 5.5 and DVB-S2 (high definition channels) will decode if SNR > 9.4. You can find the minimum SNR values for every transponder in our satellite charts.

For example, the Nasa mux on 127W on my 12' dish gives me an SNR of 15.5 dB. For a 10' antenna, you would get around 13.5 dB and around 11.0 dB for an 8' antenna. Since this is a DVB-S2 - 3/4 signal, you need a minimum of 7.9 dB to decode, so all 3 antenna sizes can decode the signal.
12ft Mesh Dish
C-Band Enthusiast since 1983

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Re: sat hero 44% versus zgemmah7 37%

Post by belter-one » Mon May 14, 2018 12:55 pm

Thank you!

Very useful information. I will re-align my dish in an attempt to get stronger signals. When I changed to "dB" units as you instructed, the satHero and the zgemma receiver were more or less in agreement. Fortunately, all three NASA channels are decoding and displaying beautifully at circa 7.5 dB:
NASA-UHD-7.5.png
I will re-align my 10' dish, in an attempt to improve reception. There are a lot of obstacles in my sky, some of which I will trim away. My low reception signal explains why I am unable to find certain FTA channels. Are there better LNBs available that could improve signal quality?

Thanks for the help,

John

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Re: sat hero 44% versus zgemmah7 37%

Post by skink » Mon May 14, 2018 9:03 pm

What are you using for a lnb now?The best way to increase that signal level is to score one of those 12 footers like fatso is using.

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Re: sat hero 44% versus zgemmah7 37%

Post by belter-one » Mon May 14, 2018 9:27 pm

Hello,

Thank you for the reply. I am using the PBI brand C band LNB sold by tek2000. A 10 foot dish was very challenging for my wonderful Wife and I to lift into position and install, so a 12 foot dish would be a last option. However, I think I can get some results from improving the alignment of the dish. There are a lot of trees, our house, and a cursed chimney I have to account for, so I am quite envious of people who have a clear sky for their C band dish(s). I have loved the results so far, and am going to install a 4 foot KU dish somewhere to get some of the interesting channels that our C band dish cannot get due to pine trees, cedar trees and chimneys. This is a great hobby, and we have already seen some wonderful 4k NASA programming that we never would have seen otherwise. Any suggestions on LNBs or other equipment that could help would be greatly appreciated.

Cheers,

belter-one.

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Re: sat hero 44% versus zgemmah7 37%

Post by skink » Mon May 14, 2018 9:45 pm

I use an orthomode feed with two separate lnbs for C band.If you get that ku band reflector up,then consider an orthomode feed for C band.I found an improvement on my 8 footer.

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Re: sat hero 44% versus zgemmah7 37%

Post by dishcrank » Tue May 15, 2018 3:52 am

Unless you got a 12 footer, most of us separate the c and ku band feeds in order to maximize the SNR levels. If you got an 8 footer, I would only use the best prime focus c band LNBF you can find. Forget about the ku band because it will degrade your c band reception and there is much more content on c band. If you got a 10 footer, you will get fairly good results with a c/ku type LNBF, but a prime-focus c band only LNBF is your best bet to squeeze an extra 1 or 1.5 dB more SNR gain. If you got a 12 footer, then you got so much gain that a c/ku type LNBF can easily be tolerated to receive both bands.

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