Finally got an STB - have questions!

[Jeffbyk]

I finally bought a Hughes E86 receiver from Flanners!  Since I am still waiting for my Directv to be installed, I am like a kid who got a bicycle for Christmas - what can you do with it.

So I did what any impatient adult male would do...I installed it into my entertainment center and hooked up my 15 year old rabbit ears.

I was surprised to see that I could get a signal strength of 100 for channel 28 (4-1) a 68 for channel 8 (10-1) and a 51 for channel 46 (1-1).  My wife and I sat in awe a couple of nights ago when we watched Leno.  We really experienced the WOW factor.

Encouraged by the results with the rabbit ears, I bought a RS double bow-tie antenna and modified it with the 300 to 75 ohm converter and tried it out tonight with CSI.  When setting it up, I found that I got a signal strength of 100 for Channel 46!!!

Unfortunately, I am learning that signal strength of 100 means little, because the picture was horrible with green pixels appearing wherever there where dark colors and edges of motion. I also noticed that the digital broadcasts of channel 4 had green pixels appear in dark areas as well (dark colors happen to be a small portion of the Leno set and are therefore unnoticable.) The next 45 minutes of adjusting position, height and angle of the blasted antenna was so frustrating it was comical.  

So, a couple of questions:
1.  Why does a signal strength of 100 not mean a perfect signal?  How can I know if my signal is strong enough to get a good picture?
2.  Why do the green pixels appear in dark areas and not light or colorful scenes?
3.  Once I get a better antenna system, will I be able to eliminate most of the green pixelization that is occurring or am I experiencing a problem somewhere else in my system?

I know that I am expecting a lot with the minimal setup I have, but the 100 signal strength has me puzzled.

Help!  

Jeff

[Gregg Lengling]

Signal strength is not always a good indicator.  You are probably receiving multi-path signals.  I don't know what your location is but I would venture to say you must be in Milwaukee County.  It takes time and patience to resolve these problems.  Many times in the past the way to eliminate this problem is to actually reduce the signal (using attenuator pads in the feedline).  I know this probably sounds funny unless you are an engineering person.  What happens in this scenario is you try to capture as much signal as possible and then reduce the signals coming down the antenna coax.  This removes the weaker signals and allows you to end up with one major signal, thus no multiple signals.  Multipath signals are especially bad in a digital format as there is an inherent time delay in any reflected signal.  The time delay causes symbol error and thus you end up with pixilation or color changes.


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Gregg R. Lengling
RCA P61310 61" 16x9

[Jeffbyk]

Thanks Gregg for your feedback!

Although I do have a BSEE, RF was my weakest area and have little practical experience working with it.  I do understand some of the basics, but I could kick myself now for not retaking some classes.

As far as multipath, I am really suspicious about the 100 signal strength.  I live in Franksville which is about 35 miles from the towers, and all I used was a RS double bow-tie through about 75 feet of RG6. Furthermore, the towers are due north from me, with nothing but flat open field for at least a few miles, so I am not sure where the multipath signals are being generated.

I did some searching on AVS and ran across other Hughes/Toshiba owners who also got 100 signal strengths and had all sorts of problems with the program guides and pixelation.  They too indicated that they booted the box with only an antenna (no dish) hooked up.  They weren't suspecting that the signal strength was faulty.  Their only solution was to get new boxes until one worked.  That sounds ugly to me.

Do you think I can get a signal strength of 100 this far away?  Where do I find the signal attenuators to filter or reduce the weak signals?

Thanks for your help!

[This message has been edited by Jeffbyk (edited 03-29-2002).]

[Gregg Lengling]

MCM Electronics has them...you can find MCM on the web at http://www.mcmelectronics.com
Just sign in as a guest and do a search for attenuator.  You will find all values.  I would suggest get about 4.....20dB, 10dB, 6dB and 3dB.  It's all trial and error without a digital spectrum analyzer.  As for getting 100 signal strength I feel that there is something with that STB of yours or just the way they measure signal strength.  These boxes give you a signal strength indication not a real signal level.  With a spectrum analyzer hooked up to your antenna you would be able to measure the real signal strength.  I'm in Cedarburg and have a DTC100 in my TV and with my high-gain antenna 45' up my tower I don't even get anything in the 90's.  Of course I'm running without a preamp and have lots of coax and splitters.  Another thought that you didn't mention, I hope you don't have a preamp on the antenna system as this can also cause problems.


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Gregg R. Lengling
RCA P61310 61" 16x9

[Jeffbyk]

Thanks for the link!

No preamp.  For a quick test (since I have them), what about using a bunch of splitters in series to see if there is an improvement.  -7dB + -3dB + -3dB...etc.

Or would this not be the same effect, especially since I will not have a load attached to the other side of the splitter?

[Gregg Lengling]

You would have to have 75ohm terminations for the unused outputs of the splitter or have them terminated into other TV's.  Open ports can change the overall impedance of the system.  On digital signals this will cause all sorts of problems, on analogue it shows up as herringbone effects and other problems.


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Gregg R. Lengling
RCA P61310 61" 16x9

[Jeffbyk]

Cool.  I have some of those, currently trying it.

[Jeffbyk]

After experimenting with different levels of attenuation, I discovered that the green pixelation was still present even when I reduced the signal to as low as a 37 where I found the receiver having trouble with locking onto the station.

But here is an interesting new twist...I fed my TWC through the Hughes box and found that these stations had the same pixelation occuring.  Should be a perfect signal, even though it is analog.  The box should upconvert the signal to 1080i and I should have a decent (albeit soft) picture. Not the case - same green noise.

So then I switch my box to display SD through the S-Video link, and all channels look good, even those received over the air on digital broadcasts.

This leads me to believe that I have good signals, but my box has a problem with its High Def output circuits.  At the very least, my analog cable channels should be noise free when upconverted, and the standard digital broadcasts, should also be upconverted properly.

What do you think?  Am I missing something in my logic?

[Gregg Lengling]

I've heard of people having bad color pixilation when the component video cables were bad.  Do you have good component video cables (IE:  Monster cables), are they a triple combo...if not are they all the same manufacturer and length.  If not this could be your problem......After seeing my 61" HD set of friend of mine with a couple year old Projection set with component video inputs went out and bought a DVD player and just used whatever cables he had laying around.  He complained about a green problem so I told him to get new cables.  For 39 dollars his problem was solved.


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Gregg R. Lengling
RCA P61310 61" 16x9

[Jeffbyk]

Gregg,

Thanks for the input.  I too suspected the cables and swapped them before I made the conclusion I did.  I have a progressive DVD player and feed both it and the new receiver into my Pioneer Elite 510 with Monster component video cables.  I even suspected a bad set of inputs on my Pioneer, but eliminated that by moving the problem from Input 1 to Input 2.

So I took the box back to Flanners and they hooked it up to test it.  The problem repeated there with a known good signal.  They gave me another box on the spot and tested it there with a perfect picture.  Woo Hoo!

My only concern is the posts I've read on AVS about hooking up an E86/Toshiba without a Satellite Dish hooked up and things getting progressively worse.  Wondering if having that input unterminated causes some degradation in their circuits or high definition tuning logic.

I know it may be paranoid, but I don't plan to use it until my dish gets installed, which will be soon anyway.

Thanks for your help because playing with the signal level made me think more about what was happening.  I will let you know how it works after I am fully up and running.

[This message has been edited by Jeffbyk (edited 03-29-2002).]

[Matt Heebner]

I dont know about the non-sat. hook-up thing. I used a RCA DTC-100 for about a month before I got the oval dish hooked up, and never had any type of problem. These STB's can be used just for OTA if you so choose. The box is under warrenty, I would just hook it up and enjoy OTA HDTV till you get the sat. hook-up.
You will wonder why you waited so long for HD!

Matt