Need advise with another CM7777 issue

[No Static At All]

He is not doing more harm than good. The CM7777 is not overpowering his TV's AGC. In most instances the worst that happens if you over boost the digital signal is the picture develops a slight background pulse in darker areas of the image.

The INPUT of the 7777 is where my concern is; not the TV's AGC. Once the input of the pre-amp is overloaded; the damage is done. You're right about TV FOOL;it isn't completely accurate. (It's been about 90% accurate for every location I've used it for) But with so many strong local stations; this is a no brainer. I would bet that Satbums antenna is getting plenty of signal for 1 TV. That is why I suggested trying just 1 TV(un-amplified), so this can be approached objectively. The 7777 is designed for weaker signal areas; not stronger ones. IMHO, only distribution losses need to be addressed in this situation.

Don't buy a sledgehammer to put a tack in the wall.

 

[Radioguy41]

The INPUT of the 7777 is where my concern is; not the TV's AGC. Once the input of the pre-amp is overloaded; the damage is done. You're right about TV FOOL;it isn't completely accurate. (It's been about 90% accurate for every location I've used it for) But with so many strong local stations; this is a no brainer. I would bet that Satbums antenna is getting plenty of signal for 1 TV. That is why I suggested trying just 1 TV(un-amplified), so this can be approached objectively. The 7777 is designed for weaker signal areas; not stronger ones. IMHO, only distribution losses need to be addressed in this situation.

Don't buy a sledgehammer to put a tack in the wall.

Iin his original post he said:

"Prior to the pre- amp install I did have a decent signal but enough pixellation and periodic signal loss to be irritating. That was the reason for the addition of the pre-amp."

So what would be the point of "trying just 1 TV(un-amplified), so this can be approached objectively." He's already done that unless you're suggesting the splitter is causing that much of a signal loss on those supposedly strong signals which would be a stretch to say the least. You can't have your cake and eat it too. Either the signals are too strong for an amp or not strong enough to handle a splitter. It can't be both. As I said earlier I'm not only running the same pre-amp but have an additional distribution amp. When I point the antenna at the local PBS station only 30 miles away the picture is perfectly clear and neither of the amps is overpowered nor is the TV's AGC. I've read all the specs on the CM7777 and no where does it say the unit can be destroyed by the signal from a close station. There are too many people who are in a similar situation as myself. I'm almost half way between two major markets with additional locals almost the full 360 degrees of the arc. The majors are almost 90 miles one way and 40 miles the other with locals as close as 25 miles. We need a strong booster to pull in the major's but it certainly will handle the locals as well. Your concern for overpowering the pre-amp is unfounded.

 

[No Static At All]

Your personal experience is not helping Satbum. OTA reception is not a guaranteed science. Every situation is unique. He needs to experiment with the process of elimination to find the proper solution. A 4-way splitter can make quite a difference with any marginal UHF signals. I'm just curious to see what hapens without the splitter or amp so a baseline can be established.

 

[Radioguy41]

A 4-way splitter can make quite a difference with any marginal UHF signals.

So now it's "marginal" signals? A couple posts ago you were adamant the signals were too strong. As I said earlier you can't have your cake and eat it too. You're only "evidence" is TVFool and that's been shown to be inaccurate. My "evidence" is based on actual experience yet you dismiss that as not helpful? You're now arguing just to win and doing it without anything to back up your position. As this exchange is going nowhere this will be my last response.

 

[No Static At All]

Thank god!!

You input has gotten us nowhere towards resolving Steve's problem. You've wasted time for both of us.

You still just don't get it!!!!

 

[Satbum]

OK guy's sorry to get back to this so late.
I could have prevented the last couple of posts if I had posted these new results earlier, but I just finished with the new modifications.

I just eliminated the 4-way switch and moved the pre-amp into the attic next to the power source or amp. When the TV in my bedroom was hooked up and the only one connected my signal was at 100%. This is the first time to experience that level. That is great news but not the perfect setup as I wanted. I figure that my 4-way switch must be the problem.
FYI: It is a 5MHz - 2.3GHz brand name Ideal with PN: 85-334.

I have now installed a couple of smaller 2-way switches to take it's place. They are 3MHz to 1000Mhz but I don't remember the brand name. I have had them for years. They seem to be working OK with the Pre-amp and amp combination, but I am experiencing some reduced power because of all of the connections.
I guess my next step in this process will be to move the pre-amp back outside and connect it to the antennae to see if that will strengthen the signal some more.
If that doesn't help, what is your next suggestion?

TIA

 

[No Static At All]

Steve,

Are you still experiencing dropouts? Are your problem channels only on VHF?

 

[Satbum]

I believe that my trouble channels now are UHF mostly but I do have reduced signal on the others because of all the connections and multiple splitters.

Like I said, I will move the pre-amp back outside and put it onto the antennae to see if that helps before I proceed to the next step looking for a amplified distribution box or another 4-way splitter.

Update - I moved the pre-amp back to the antennae and gained about 5- 10 % gain in signal, but I still experience that periodic signal drop.

 

[No Static At All]

Have you ever tested for multipath by checking for ghosting on analog channels? The dropouts can also be caused by excessive multipath.

 

[Satbum]

Have you ever tested for multipath by checking for ghosting on analog channels? The dropouts can also be caused by excessive multipath.

No that is new for me.
The analog is terrible and you can hardly even see it. Only the SD and HD are decent to look at.

I will do some research to see what you are talking about.

TX Again...

 

[Jim5506]

Is analog terrible because of snow (weak signal ) or because of multiple overlpping images on the screen (multipath)?

 

[No Static At All]

Or is it more like squiggly lines and herringbone patterns?

I just read about someone with a similar pre-amp situation in another forum. Here is the response that was given by a certified engineer.

"You have a large number of fairly strong LOS stations that can cause intermodulation noise in the high gain CM-7777. This can desensitize certain weak channel positions.

One of the medium gain W-G Preamps would be better, such as AP-8700:
http://www.winegard.com/offair/pdf/Chart29.pdf
http://www.winegard.com/offair/preamps.htm

In addition to improving overall sensitivity (typ 10 dB), the Preamp will
also overcome loss in coax, 4-Way RF Splitter...and tuner Noise Figure"

 

[Radioguy41]

Thank god!!

You input has gotten us nowhere towards resolving Steve's problem. You've wasted time for both of us.

You still just don't get it!!!!

Excuse me? I've stayed out of it for a few days and you're not any closer to resolving it. Before you continue to give him bad information you might want to look up the specs for a CM4228 antenna. It's UHF only so there's no point in even addressing any VHF issues. In fact a better choice for a pre-amp would have been a CM4775 (UHF only). More pertinent questions might be:

Are you running RG6 coax cable?
Do you have the antenna coax connected to the UHF/Combined connection?
Is the Combined switch set to "Combined"?

It might be more helpful to ask under what conditions he experiences those dropouts. For instance, if there is any kind of aerial flightpath anywhere near his LOS he will experience dropouts and there is nothing that can be done. It's an inherent failing of digital broadcasting. If you really want to help the guy ask pertinent questions and spend less time trying to be king of the hill.

 

[No Static At All]

I know the 4228 is a UHF only antenna; but many users do have luck with HI-VHF on closeby stations. I personally don't prefer bowtie antennas. They can be great performers; but are very environment specific. They just don't work well in high multipath areas.

As far as not having the problem resolved yet; thats up to Steve. He is agressively trying different things to acheive results he deems satisfactory.

I still stand by my original conclusion of amplifier overload. The antenna choice may need to be addressed also if no resolution is reached.

You were commenting on how I was referring to strong signals; then weak signals. Many areas(like Steve's) have a blend of strong and weak signals. If you want to receive the weaker signals; you must avoid any kind of over-amplification. The weaker stations will be lost; not the stronger ones. I personally use no amplification, and still experience a slight amount of overload; which is controlled by careful height adjustment. My results far exceed my expectations. Experimentation is the key.

Getting great reception is more of a challenge for some than others. It's great that you are getting good results with the CM 7777; but it isn't going to work for everyone. I have used the 7777 at different locations; but my experience with signal levels like Steve's has not been positive. It is an excellent pre-amp under the right conditions.

 

[No Static At All]

Jeepguy,

As far as the RG-6 cable goes; that is an excellent question. I've already had some dis-agreement about RG-59 vs RG-6 with others on this forum. IMO, UHF or higher frequencies are a much better bet with RG-6, and in some cases, RG-11. I would never use RG-59 for anything except VHF only, or a very short cable run with UHF. The small cost difference isn't worth the gamble of the higher db loss penalty inherent to RG-59 cable.

 

[Satbum]

Is analog terrible because of snow (weak signal ) or because of multiple overlpping images on the screen (multipath)?

Jim - I think my problem may be multipath from what I have read on it.
I am experiencing what both you and No Static At All has described.
When I am on the HD channels the picture is great as a rule but I do get a lot of drop and and minor pixels. They just don't last long.

I have ordered the Channel Master CM 3414 Distribution Amplifier (CM3414) to use vice the old splitters that I have now. I also have a couple CHANNEL MASTER 7270 Attenuator UHF/VHF/FM 75 OHM on order to adjust the signal freqs.

jeepguy:

Are you running RG6 coax cable?
Do you have the antenna coax connected to the UHF/Combined connection?
Is the Combined switch set to "Combined"?

Yes to all of above.

No Static At All - a different antennae is out of the question until this one is broke. I will make this work the way I want some how.
I am anal that way. LOL

This is an on-going challenge, but I am learning as I go.

Thanks and I will let you know my future results.
I don't expect my new parts until next week some time.