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Re: Occasional "burps" on U4K?
To: CRTech <crtech@crtech.org>
Subject: Re: Occasional "burps" on U4K?
From: Mike Shane <mshane@salemomaha.com>
Date: Tue, 20 Feb 2018 02:06:22 +0000
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Thread-topic: [CRTech] Occasional "burps" on U4K?
Check power supply on U4K. 

Mike Shane

On Feb 19, 2018, at 17:28, Michael Barnes <barnmichael@gmail.com> wrote:

Also, remember that Eb/No is a calculation of several values over time and runs a bit behind actual events. Transient events will not be reflected in any Eb/No reading. As I haven't seen a U4K in almost two years, I don't remember specifically what the red LED is for, but I suspect it might be indicating a brief unlock in decoding the data stream. This could be caused by an RF disruption or something failing in the receiver. Considering the age of the U4K (~20 years?) there could be any number of possibilities. Might I suggest starting to look for a Unity 4600 or newer receiver?


On Mon, Feb 19, 2018 at 12:36 PM, Sherrod Munday <smunday@ieee.org> wrote:
On Feb 19, 2018, at 14:23, Willie Barnett <wbradiolists@gmail.com> wrote:
The EBNO hovers around 10. When I heard the "blurps", I quickly looked at the receiver noticed the red LED blink ever so briefly, and the EBNO dropped briefly to about 9. The "blurping" only started about a month ago, and seems to be random. (That's why I said 0 to 4 times per newscast.) They usually only take out a word or two. They're fairly short.
Our receivers are fed by the same dish.


While it could be a failing U4K, I'd suggest that you start with the more mundane.  What you're describing sounds like a classic case of interference.

* RF connections between the dish and splitter:
  * Ensure the connectors are snugly connected to the jacks
   * Check the coax line to ensure it's not crimped/bent/nicked
   * Check the shield to ensure it's not broken anywhere on the line

* Possible local TI (terrestrial interference) that the receivers may handle differently due to different design and performance

* Check the splitter itself to ensure you don't have a faulty port. It happens.

* Look at a spectrum analyzer when you hear those chirps, if at all possible.  Set up a webcam in front of the display and use something like ContaCam (free Windows motion-detect & archive program for webcams) to record changes over time or brief hits on the RF.

* Check your RF levels, like Mark said. Be aware that the U4K may have a tighter tolerance for this spec than the AMR.  Try 3- or 6-dB attenuators or an adjustable RF amp as one pair of possibilities.  Don't forget to look and experiment on both sides of the splitter.

* Check the alignment of your dish and LNB. Again, I recognize your single dish feed goes to all the receivers, but it still merits a trip outside to confirm.

(Speaking of: the upcoming solar transit outage is a perfect time to check for obstructions in the path of the satellite dish during peak signal loss.  See the recent article in Radio World for pictures and an article about this.)

I hope these suggestions help!

Sherrod Munday

Follow-Ups: Re: Occasional "burps" on U4K?
(Alan Kilgore <wrvm.engineer@gmail.com>, 20 Feb 2018 14:24:55 -0000)
References: Occasional "burps" on U4K?
(Willie Barnett <wbradiolists@gmail.com>, 19 Feb 2018 18:12:19 -0000)
RE: Occasional "burps" on U4K?
("Allard, Mark G" <MGAllard@unwsp.edu>, 19 Feb 2018 18:32:41 -0000)
Re: Occasional "burps" on U4K?
(Willie Barnett <wbradiolists@gmail.com>, 19 Feb 2018 19:23:38 -0000)
Re: Occasional "burps" on U4K?
(Sherrod Munday <smunday@ieee.org>, 19 Feb 2018 20:36:12 -0000)
Re: Occasional "burps" on U4K?
(Michael Barnes <barnmichael@gmail.com>, 19 Feb 2018 23:28:11 -0000)
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