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Guest Message by DevFuse

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Rain fade


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14 replies to this topic

#1 OFFLINE   GirkMonster

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Posted 30 March 2007 - 07:32 AM

Anyone experience more frequent rain fade with the Slimline dish compared with the older triple-LNB dish?

Related question, why would the HR20 demonstrate something similar to rain fade using an attic-mounted OTA during a significant storm? It was much more brief than the Sat channels, but surprising to me nonetheless.

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#2 OFFLINE   gabe23

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Posted 30 March 2007 - 07:42 AM

Anyone experience more frequent rain fade with the Slimline dish compared with the older triple-LNB dish?

Related question, why would the HR20 demonstrate something similar to rain fade using an attic-mounted OTA during a significant storm? It was much more brief than the Sat channels, but surprising to me nonetheless.


In my experience, the Slimline dish is much better at avoiding rain fade than the older dish. Also, my OTA is sometimes affected by strong storms on any tuner (H20, TV tuners), so I don't think that's an HR20 problem.

#3 OFFLINE   GirkMonster

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Posted 30 March 2007 - 07:45 AM

Thanks. I don't think it lasted very long and the storm was fairly severe. I went to the OTA because a local station has 24-hour weather on one of its digital multiplex channels.

#4 OFFLINE   Tom Robertson

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Posted 30 March 2007 - 12:01 PM

Anyone experience more frequent rain fade with the Slimline dish compared with the older triple-LNB dish?

Related question, why would the HR20 demonstrate something similar to rain fade using an attic-mounted OTA during a significant storm? It was much more brief than the Sat channels, but surprising to me nonetheless.


Wow, that was a gully washer and raining cats and dogs! I've had zero rainfade with my AT9 since it was installed (and I forced the installer to align it correctly). We don't get many rainstorms, but they can be intense.

Next cloudy/rainy day compare your signal strenghts on 99° and 103°. The spot beam for your locale should drop a little, but still be above 75. Everything else might fall off completely (I only have one of all 13 transponders that is higher then 50. And its 95 most of the time.)

Cheers,
Tom

Go Packers!

My real treasures: 5 Grandchildren - S, D, M, M, C ; Now 5! Great-Grandtibbers - B, H, J, A, and M (Born 7/31/2011)


#5 OFFLINE   veryoldschool

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Posted 30 March 2007 - 12:10 PM

Wow, that was a gully washer and raining cats and dogs!

After "cats & dogs", it becomes "lions and tigers and bears, oh my".
I get them here too.:)
A.K.A VOS

#6 OFFLINE   Tom Robertson

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Posted 30 March 2007 - 12:13 PM

After "cats & dogs", it becomes "lions and tigers and bears, oh my".
I get them here too.:)


The two desert and near-desert locations I've lived, Phoenix and Salt Lake, have produced some of the more intense storms I've seen. And in Phoenix it was a yearly event. Here in SLC, not quite so often.

Cheers,
Tom

Go Packers!

My real treasures: 5 Grandchildren - S, D, M, M, C ; Now 5! Great-Grandtibbers - B, H, J, A, and M (Born 7/31/2011)


#7 OFFLINE   bonscott87

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Posted 30 March 2007 - 01:01 PM

I have had OTA issues before in very intense storms. It's usually the lightning between me and the towers. Most of the time is really, really bad lightning at the towers, not at my house.

This has happened twice in the past 3 weeks and both times there was nothing going on at my house or for 20 miles around. But the location where the towers were was getting hammered.

#8 OFFLINE   94SupraTT

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Posted 11 April 2008 - 05:24 PM

Anyone experience more frequent rain fade with the Slimline dish compared with the older triple-LNB dish?

Related question, why would the HR20 demonstrate something similar to rain fade using an attic-mounted OTA during a significant storm? It was much more brief than the Sat channels, but surprising to me nonetheless.

I'm having this very issue with my Slimeline dish. I live in tornado alley and the 3LNB dish rarely experienced rainfade whereas I'm almost guaranteed to lose signal for moderate storm with the Slimline.
50" P50H401 Plasma / HR20-100
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#9 OFFLINE   Hansen

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Posted 11 April 2008 - 05:58 PM

Come to Texas where the intensity of the storms are on par with the size of Texas. .
HR20-700 (networked) with 750gb eSATA drive via HDMI to Panasonic 42" HD plasma
HR20-700 (networked) via HDMI to Pioneer 50" HD plasma with customized URC Complete Control MX-3000 touch screen remote using RF
HR20-700 (networked) via HDMI to Samsung 19" HD LCD
H20-100 via HDMI to Toshiba 19" HD LCD
H20-100 (now retired and collecting dust) via HDMI<DVI to Sony 42" HD plasma
H21-100 via HDMI to Sony 40" HD LCD (in outdoor pavillion)

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#10 OFFLINE   glennb

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Posted 11 April 2008 - 06:09 PM

The OTA transmission is digital just like the digital satellite transmission.

The OTA will be affected by heavy rain or wet snowstorms.

#11 OFFLINE   GTS

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Posted 11 April 2008 - 06:18 PM

Wow, that was a gully washer and raining cats and dogs! I've had zero rainfade with my AT9 since it was installed (and I forced the installer to align it correctly).


This problem is becoming more and more prevalent. The installers are cutting corners by not performing the dither alignment and thus not truly peaking the dish for the Ka birds. If they don't have a meter capable of seeing the 99 and 103 satellite signals they must perform the dither or the dish simply is not peaked. Thre's no reason a properly installed and aligned dish can't achieve a signal level in the 90s on the 99 and 103 birds. I've seen a lot of "so long as the signal is above 70 it's fine", but this is not so. The biggest problem caused by this misconception is "premature fade".

#12 OFFLINE   TomCat

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Posted 11 April 2008 - 07:45 PM

In my experience, the Slimline dish is much better at avoiding rain fade than the older dish. Also, my OTA is sometimes affected by strong storms on any tuner (H20, TV tuners), so I don't think that's an HR20 problem.

It rarely rains where I live, but my numbers went up an average of about 15 points when I replaced my Phase III with a Slimline. That leads me to a conclusion that the Slimline is hotter, since I vetted precise alignment myself on both dishes (and I used the HR20 to align both, so no, it's not a HR2x issue).

It may be as simple as a poor aiming job. The Slimline is much more critical for the Ka channels (most of MPEG-4 HD is on Ka). IOW, you can be aligned half-assed for Ku and still get good numbers on those transponders, but it takes precise alignment for the Ka transponders because since the downlink frequency is higher, the focal points are more focused, and therefore about 1/3 the size of a Ku focal point. Also, wind-loading is an issue with a larger, heavier dish, which means bracing struts are commonly used. Make sure your Slimline has those, and install them if you don't have them.

The OTA interference problem is similar because the attenuating mechanism is similar (objects, such as rain drops, getting in the line of sight and absorbing or reflecting the signal). Both UHF/VHF and microwave (sat) have rain-fade issues.

#13 OFFLINE   TomCat

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Posted 11 April 2008 - 08:07 PM

...The installers are cutting corners by not performing the dither alignment and thus not truly peaking the dish for the Ka birds. If they don't have a meter capable of seeing the 99 and 103 satellite signals they must perform the dither or the dish simply is not peaked...

Well, not exactly, although I agree with your suspicion that installers are doing a rush job on Ku and leaving it at that. For them, doing a precise alignment on a dish they don't own is like getting an oil change in a rental car. Why should they care?

By "not exactly" I mean that Slimline alignment is done on the Ku sats, not on the Ka sats (or at least not if following the instructions). If done precisely to 110/119, the Ka sats fall directly in line. You don't need a Birdog or digital SLM to do this accurately, although that helps speed the process. I had the advantage of being able to stand on my balcony and adjust the dish while watching my 60" Sony through a picture window 8 feet away, so I guess it seemed simple, but if you really want to get accurate, schlep a TV and HR2x (and power) out to your dish.

Download the Slimline manual (Google is our friend) and simply follow the directions, and remember that dithering precisely is the key, and dithering precisely means using the "outside" of each matching number, not the "outside" of one and the "inside" of the other (once you get the concept, that will make sense, trust me). I had mine done in half an hour, and when the installer (finally) arrived he could not improve the numbers using his meter, though he seemed motivated to prove he could, not even at all.

Bottom line, whether you have a meter or not, dither, dither, dither. And once you get there on 119/110, repeak on the Ka sats (even though that isn't really in the instructions or even necessary if done properly to Ku in the first place) as that verifies max rain fade on HD.

#14 OFFLINE   Kansas Zephyr

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Posted 11 April 2008 - 08:18 PM

The OTA transmission is digital just like the digital satellite transmission.

The OTA will be affected by heavy rain or wet snowstorms.

Digital vs. analog isn't the issue here.

The higher frequency (satellite) will suffer more from attenuation by rainfall/snowfall, versus the lower (OTA) frequencies.

In a case where you have the same signal strength to start with sat/OTA, you will always lose the sat signal first, and get it back last.
5 LNB Slimline & SWM-16
SWM1 2 HR20s & HR21 via SWS-4 "green label" 4-way splitter w/power pass one leg for PI - SWM2 2 HR20s & HR21 after SWS-4 "green label" 4-way splitter
2 HR20-700 Wireless network for DoD
HR20-700 eSATA Vantec NexStar CX w/ 2TB WD20EVDS
HR21-100/AM21 Wireless network for DoD
HR21-100/AM21
With diplexed OTA via an "out" on one SWS-4 4-way splitter, using a Winegard YA 1713 - Channel Master 4228 - Channel Master 7777 in the attic.
Yes, my market has HD LiLs...and I'm still not giving up OTA! No rain-fade, and all sub-channels 24/7/365.
Also, with diplexed Cox Internet on one leg, downstream of a SWS-4 4-way splitter, using a SWS-2 2-way splitter, as a combiner.
R10 via SWM-16 Legacy 1
In boxes HR10-250, HDVR2 & (2) D10-300

#15 OFFLINE   TomCat

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Posted 12 April 2008 - 08:09 PM

...The higher frequency (satellite) will suffer more from attenuation by rainfall/snowfall, versus the lower (OTA) frequencies.

In a case where you have the same signal strength to start with sat/OTA, you will always lose the sat signal first, and get it back last.

Comparing signal strength for sat and OTA is an "apples vs. oranges" issue. Whether you get OTA back first or not depends on the comparitive amount of rain fade margin, which will be quite different depending on how far away the OTA towers are from any particular receive antenna. Different transmit and receive systems have different rain fade margins designed into them, and these systems are very different.

That said, there is a very simple reason why rain is more destructive, all else held equal, to sat downlink signals vs. OTA signals, which is that Ku and Ka wavelengths are very similar in size to raindrops, while UHF wavelengths are significantly larger than raindrops. Raindrops are like little "roach motels" to sat signals--signals go in, but they don't come out. Since the raindrop is the same size as the wavelength, the sat signal causes the raindrop to vibrate sympathetically at frequency, and instead of passing through and refracting, much of the signal is converted to heat, thus attenuating the aggregate signal level. That doesn't happen with OTA signals.

What that means is that raindrops can both absorb and refract the sat signal, but those same-sized raindrops can not significantly absorb OTA signals, they only can refract them. The corresponding attenuation is therefore much higher at Ka/Ku frequencies. It's simple physics.




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