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Old 16-Aug-2014, 3:11 AM   #1
joshg0207
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signal overload

I have an antenna on a 40 foot tower with a channel master 7777 pre amp hooked to it I think I'm experiencing overload from a nearby station...my question is can I use a variable attenuator to back down the amount of signal and if so where would be the proper placement of the attenuator be.
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Old 16-Aug-2014, 3:18 AM   #2
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This is my tv report... **http://www.tvfool.com/?option=com_wr...5b9409cb14b836
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Old 16-Aug-2014, 4:44 AM   #3
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What is the make and model number of the antenna??

Is the antenna a amplified antenna and the CM7777 is amplifying the amplified antenna??

If not known what antenna you have what antenna Picture looks the most like the antenna??

www.kyes.com/antenna/pointing/pointing.html

Last edited by teleview; 16-Aug-2014 at 5:37 PM. Reason: Clarify information and typos.
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Old 16-Aug-2014, 5:56 AM   #4
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Have you tried removing the CM-7777 and it's power supply? The CM-7777 is for applications were no strong signals are present. If you need a preamplifier to drive a long run of coax or to overcome the losses incurred while splitting the signal, preamplifiers such as the RCA TVPRAMP1R or distribution amplifiers like the CM-3410 are better suited to the stronger signal levels shown in your report.

It sounds like this is a continuation of your earlier thread, http://forum.tvfool.com/showthread.php?t=14300
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Old 16-Aug-2014, 6:57 PM   #5
joshg0207
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My antenna is a channel master cm 3020...I think it is the amplifier is to strong and overloading the signal...it's on a 40 foot tower so I can't get to it to remove it with out climbing the tower...I was wondering if there was anything i could do to lessen the amount of signal with out climbing the tower
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Old 16-Aug-2014, 8:29 PM   #6
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I think you're close... I believe the amplifier is overloading. Signals are not making through the CM-7777 without being distorted and reduced in quality to the point of being unusable.

In this case, I doubt that the gain of the amplifier is so high that the tuners are being over driven.

Amplifiers do not add to the gain to an antenna. They only deal with the loss in cable and splitters connected on the output side of the amp.

If I was in your situation, I would be putting my safety harness on, heading up the tower to remove the CM-7777. Adding attenuation ahead of the amp or using a lower gain antenna is the only way to reduce signal levels to the point where the CM-7777 might operate in an non-overload state. Both of those options would be self defeating, as it reduces the net gain of your antenna and also subtracts from your net noise margin. (And both options require going up the tower!)

I'm sorry, but the CM-7777 is not the right amplifier in your application. Even Channel Master's ad copy warns against selecting the CM-7777 when there are any stations within 80 miles.
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Last edited by GroundUrMast; 16-Aug-2014 at 9:03 PM.
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Old 28-Feb-2015, 10:13 PM   #7
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So I finally had someone come out and climb the tower and change the preamp to an rca tvpramp1r...I'm still having problems receiving channels reliably...I still think there might be some overloading going on from the line of sight tv stations that are 10 miles away...The main station is whag...I was wondering if I could try a wineguard ut 2700 uhf trap to attenuate some of whags signal since it's so strong...what gets me is my dad has the exact same setup and lives only a half of a mile away and gets way more channels...The only thing that is different is his antenna is 20 ft high and mine is 40 ft high...does anybody have any thoughts on what else I can do to improve reception.
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Old 1-Mar-2015, 12:04 AM   #8
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Do you have the FM trap turned on?
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Old 1-Mar-2015, 12:23 AM   #9
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Yes I made sure of that...wonder if it's possible that I need a second fm trap
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Old 1-Mar-2015, 12:54 AM   #10
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Sorry if I missed it, but what makes you suspect that overload is the problem?

Are all of your channels breaking up? only some of them? only weak ones?

Are there specific channels you would lose if you did not have the pre-amp?
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Old 1-Mar-2015, 1:10 AM   #11
joshg0207
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I'm just suspecting it's overload because I have strong channels close by...When I check the signal on those channels with my zenith tuner the signal meter is just about maxed out...and also my dad has the exact same setup and I can just about see his house from mine...I guess I could be wrong maybe it's the position of the antenna maybe it's to high...His is 20 ft off the ground and mine is on a 40 foot tower.
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Old 1-Mar-2015, 2:30 AM   #12
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I seriously doubt it's overload. What antenna is your father using?
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Old 1-Mar-2015, 2:36 AM   #13
joshg0207
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He is using the same antenna and pre amp...The antenna is a channelmaster cm-3020 and the pre amp is a rca tvpramp1r...There are 2 differences between our setups antenna height and he has 50 ft of rg6 coax and I have 100 ft of rg 11 coax...
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Old 1-Mar-2015, 7:02 AM   #14
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So what symptoms are you seeing? Which channels are the ones giving you problems?
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Old 1-Mar-2015, 8:02 AM   #15
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PA. DTV reception

The antenna is more than needed for reception of the available channels at your location, and the amplifier is most likely overloading. Just remove the amp. If your connections and coax are good, the amp is out, and the problem is still there, you could have an interference issues.
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Old 1-Mar-2015, 5:17 PM   #16
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Quote:
Originally Posted by mtownsend View Post
So what symptoms are you seeing? Which channels are the ones giving you problems?
Exactly, this is the info needed to properly diagnose.

Also, I don't see any overly "strong" stations. You mention "10" miles away. Is the TV fool report accurate?
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Old 1-Mar-2015, 9:26 PM   #17
joshg0207
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Hey signals unlimited...I see your located in south central pa...that is were I'm from I'm trying to pick up the dc and baltimore stations...I know you said to take the preamp out and I will try that...is there anything else I can do if it is indeed interference from something else...I'm just trying to get your thoughts on my situation since your from the same area
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Old 1-Mar-2015, 9:56 PM   #18
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PA. DTV reception

Joshg. I sent you a PM.
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Old 2-Mar-2015, 6:46 PM   #19
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When I review this thread and the parallel thread, http://forum.tvfool.com/showthread.php?t=14300, I come to the conclusion that I/we failed to challenge some of the basic issues...

Before we can determine if an amplifier is needed or not, we need to be sure the antenna, it's location and aim are appropriate.

Based on the signal report provide, a large deep fringe all channel antenna such as the CM3020 does not appear to be the best option. Given it's rather directional qualities, it's not likely that any single aim point would offer reliable reception of all the available signals. Also, the L-VHF + FM capability of the CM-3020 is not needed and may be responsible for or at least add to an FM interference problem.

I don't see were we asked about surrounding structures and foliage... If aiming into a building or nearby trees, reliable reception may be impossible despite the tower and antenna gain.
The fact that the antenna is on a tower and difficult to get to, doesn't change that reality that reliable reception starts with specifying the correct antenna, then locating and aiming it properly.

Though it may be difficult, testing reception at the antenna, with no amplification or splitting installed would be my next step... http://forum.tvfool.com/showthread.php?t=13646. Only after I had proven the antenna is producing a reliable signal would I turn my attention to the question of amplification.
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Old 2-Mar-2015, 10:18 PM   #20
joshg0207
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The antenna is not facing any buildings or trees...I am starting to agree with you I don't think I have the right antenna...I bought a antennasdirect 91xg and bolted it to the side of the tower about 20 ft up the tower and pointed it in the direction of the baltimore and dc stations and are picking up the uhf stations that are way down the list on my tv fool report or not on there at all...so it definitely could be the antenna and the positioning of it...
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