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Old 6-Feb-2018, 1:22 AM   #1
760side
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signal quality help

So Im looking for some insight into why my signal quality is so low. I think it might be due to my CM 7777 (Older model uhf/vhf input) but wanted to get some feedback.

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set up is below:
UHF Antenna (91 XG)
|
CM7777- 40ish feet of coax- CM Power supply inside-->TV
|
VHF Antenna (antenna craft yagi vhf antenna)

Is this a situation where a variable attenuator would help with the signal quality?
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Old 6-Feb-2018, 2:52 AM   #2
rabbit73
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Quote:
Is this a situation where a variable attenuator would help with the signal quality?
No

You were doing so well with channel 40 in your last thread, what has changed since then?
Suggestions for improvements?
http://forum.tvfool.com/showthread.php?t=16060
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Old 6-Feb-2018, 3:05 AM   #3
760side
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Well I have the CM7777 now which I dont believe I had as of my last thread. Thats all thats really changed. 95%-98% of the time the picture is solid. I get an occasional drop and an extended drop of 4-6 seconds every now and then.

I just wanted to revisit the issue...since the signal quality is the last thing Im having a problem with.
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Old 6-Feb-2018, 2:05 PM   #4
rickbb
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You're signal at 100% but quality is only 56%.

This tells me to look at noise and/or overload. You're getting plenty of signal, just a crappy one. Or the tuner doesn't know what to do with it.

I couldn't use the CM7777 due to overloading, I went with a Wineguard PA100, (not sure of the exact model I'm at work and can't look it up now), it has an adjustable gain and I could dial it up to overload then back down to just under overload. Solved the issue I had well.
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Old 6-Feb-2018, 2:50 PM   #5
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Quote:
Originally Posted by 760side View Post
Well I have the CM7777 now which I dont believe I had as of my last thread. Thats all thats really changed. 95%-98% of the time the picture is solid. I get an occasional drop and an extended drop of 4-6 seconds every now and then.

I just wanted to revisit the issue...since the signal quality is the last thing Im having a problem with.
You have the original 7777 which doesn't overload easily, and all your signals are weak.

Is the problem only with channel 40, or all channels?
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Old 6-Feb-2018, 6:15 PM   #6
760side
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It is on all channels, see attachments
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File Type: jpg 2.JPG (27.4 KB, 39 views)
File Type: jpg 3.JPG (27.6 KB, 42 views)
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Old 7-Feb-2018, 1:00 AM   #7
rabbit73
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OK, thank you for the images.

So, it isn't just channel 40.

There must be something wrong with your equipment or you have a serious interference problem.

Your signals are strong because of the antenna and preamp gain, but something is reducing the SNR of your signals.

Since it is intermittent, it will be difficult to diagnose.

The only thing I can think of now is to substitute each and EVERY part of your system with a known good part, even if it means ending up with a completely separate test system.

To check for interference, listen for noise on a battery operated portable radio that tunes the AM broadcast band.
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Last edited by rabbit73; 7-Feb-2018 at 1:04 AM.
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Old 7-Feb-2018, 3:25 AM   #8
760side
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So some more clarification when I say intermittent the signal strength is always around 100% and the signal quality is in the 40%-50% range. Its the picture itself that is intermittent. Im able to watch TV with those numbers with an occassional picture drop.

As for a battery powered AM radio is there a specific channel I should be listening on? I guess I could google how to troubleshoot OTA with AM radio
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Old 7-Feb-2018, 7:05 AM   #9
OTAFAN
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As for a battery powered AM radio is there a specific channel I should be listening on?

Try either far down on the low end of the dial, say 540-590AM (stay away from KOGO 600AM San Diego, since you're in Oceanside), or up at the top end 1600-1700AM, where you cannot hear much of any station, rather just plain "noise." Then as you walk around your area any interference will grow louder on your radio as you pick it up.

For instance, if you place your radio near your TV, or microwave oven while turned on, or CFL light bulbs if you have them, you'll hear a peak in volume as interfering noise.

Then you can go on the hunt to see what might be strong interference around your antenna set up. You'll probably need to turn some things off around your home for process of elimination. Or, possibly there might be some strong interference coming from nearby such as power lines, etc. or a neighbors house next door. Again process of elimination.

Good luck!

Last edited by OTAFAN; 7-Feb-2018 at 7:06 AM. Reason: wrap quote mistake
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Old 7-Feb-2018, 7:16 PM   #10
rabbit73
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OTAFAN covered it pretty well. Try an unused frequency at the high end and low end to listen for electrical interference noise. Electrical interference on the AM band can be strong enough to affect TV reception. The loop antenna in the portable radio can act as a direction finder. In addition to CFLs, LED lamps can also create noise interference.

Good luck hunting for the reason your Signal Quality (SNR) is so bad.
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Last edited by rabbit73; 7-Feb-2018 at 10:46 PM.
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Old 7-Feb-2018, 10:54 PM   #11
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Quote:
OTAFAN covered it pretty well.
Thanks rabbit73! I've been learning from The Great One (you) on this forum and your humble assistant appreciates your continued posts. Long may you live.....we need you going forward during these Repack days.....
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Old 8-Feb-2018, 2:46 AM   #12
760side
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As always I appreciate the help. I checked my cable and it is RG 6U CCS. I was thinking I may swap that out with the RG 6 quad shield solid copper. and My run is definitely more that 40 ft...probably closer to 60 or 70 feet since it does go through the attic and up to the the second story where both of my antennas are located.
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Old 8-Feb-2018, 6:35 AM   #13
OTAFAN
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You're probably aware of keeping your cable run as straight as possible, certainly no tight coils or bends (basic cable installation), as this will attenuate your signal. I don't think 60 or 70 feet will loose too much on your TV signal meter, some but not that much according to some charts I've seen on the Web. I have nearly 90 feet on my cable run, but I live in a strong signal area. However, I have found sometimes that I needed to repair or change my cable to receive optimum signal. And RG6 Quad has served me well here too. Hope this helps.....
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Old 11-Feb-2018, 10:17 PM   #14
760side
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Well it looks like I may have FINALLY solved my problem. I pulled new rg6 quad shield solid copper. I also used new compression fittings and a dab of dielectric grease on all the outdoor ends. I inspected the old coax and there were a few really bad kinks in it that Im assuming were a big part of the problem.

The attached readings are with the new cables.
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File Type: jpg 1.JPG (28.0 KB, 36 views)
File Type: jpg 2.JPG (28.1 KB, 32 views)
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Old 11-Feb-2018, 11:40 PM   #15
rabbit73
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Thanks for the report; that's much better!







For testing, I actually use a short length of the 18 gauge center conductor from Copper Clad Steel RG6, it is more rigid than solid copper.

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Last edited by rabbit73; 12-Feb-2018 at 1:06 AM.
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Old 12-Feb-2018, 4:44 AM   #16
OTAFAN
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Congratulations 760side on the better reception!

And thanks a million rabbit73 for posting the pics above. I will file this for my future reference. BTW, I think you posted previously about how to test coax cable to see if it was good for reception before you hook it up? Would you mind linking it up here? I haven't been able to find it so far. Thanks again.....
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Old 13-Feb-2018, 12:05 AM   #17
rabbit73
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Quote:
Originally Posted by OTAFAN View Post
BTW, I think you posted previously about how to test coax cable to see if it was good for reception before you hook it up? Would you mind linking it up here? I haven't been able to find it so far.
OK, here it is:









Attached Images
File Type: jpg TestingCoax1.jpg (198.3 KB, 219 views)
File Type: jpg TestingCoax2.jpg (196.2 KB, 211 views)
File Type: jpg TestingCoax3.jpg (201.7 KB, 216 views)
File Type: jpg TestingCoax4.jpg (193.0 KB, 214 views)
File Type: jpg TestingCoax5.jpg (215.4 KB, 211 views)
__________________
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Last edited by rabbit73; 13-Feb-2018 at 12:11 AM.
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