Tacoma, WA: What are symptoms of overloading? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 13 Old 02-29-2020, 11:22 PM - Thread Starter
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Tacoma, WA: What are symptoms of overloading?

Hello! my zip is 98374.
I am running an old C/M 4228 (not newer HD model) through a 7777 preamp. My signal strength varies ALOT. So much so that the the meter will repeatedly drop from the 60-70 range all the way to zero for a few seconds or up to a minute. At first I thought it might be the breeze moving around some very tall Evergreen trees 1000 to 3000 feet in front of my antenna. But I noticed it also does this with no wind at all. I keep reading that the 30dB gain from the 7777 often overloads the input stage of tuners, but could overloading possibly cause what I am experiencing? The 55 feet of RG6 quadshield from the 7777 to the Dish VIP622 goes through one grounding block and of course the preamp's power inserter, but no splitter, combiner, or anything else! I know my receiver uses ancient technology, but I just cannot figure this out...any ideas out there?
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post #2 of 13 Old 03-01-2020, 06:54 AM
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Please read the stickies at the top of the thread and post a link to your Rabbitears report so we have some idea what sort of signals you have. If you don't have enough posts to post a link then PM Dr. Don to do it for you or add a couple of spaces to the link so it'll post. We also need more details on your setup. Where is your antenna? Is this happening on all stations? Some stations? Which ones?

So far your description does not sound like overloading. Overloading typically shows up as not being able to receive stations that you would otherwise receive absent the overload. The stations never come in. The type of intermittent reception you're reporting sounds more like interference of some sort but we need a lot more information.

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post #3 of 13 Old 03-01-2020, 07:25 AM
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New install or old install?
If old, did it ever work without issue(s)? If yes, when did the problem(s) start?
Is the VIP622 being used for OTA only?



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
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post #4 of 13 Old 03-01-2020, 07:51 AM
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Quote:
Originally Posted by Starlifter-f/e View Post
Hello! my zip is 98374.
I am running an old C/M 4228 (not newer HD model) through a 7777 preamp. My signal strength varies ALOT. So much so that the the meter will repeatedly drop from the 60-70 range all the way to zero for a few seconds or up to a minute......I keep reading that the 30dB gain from the 7777 often overloads the input stage of tuners, but could overloading possibly cause what I am experiencing?
Hello, Starlifter-f/e; welcome to the forum.

As mentioned by Calaveras and Ratman, we really need more information to help you.

To answer your question, your signals are strong enough at the center of your zip code to cause overload with your old 4228 and the 30 dB 7777 preamp, if your antenna is outside and in the clear. KBTC on real channel 27 would have a TVFool report Noise Margin of more than 95 dB after adding the antenna gain and the preamp gain. Other possible causes are a poor connection, equipment failure, or LTE (cellular) interference.



This is a TVFool report for the center of the zip code in Puyallup, WA, just south of Seattle:
http://www.tvfool.com/?option=com_wr...9038ebb235e0e4



Small changes in location can make a big difference in the signal report.



This is a report from rabbitears.info, also for the center of the zip:
https://www.rabbitears.info/searchma...study_id=65059

You can do a rabbitears.info report here; it should be more up to date than a TVFool report:
https://www.rabbitears.info/searchmap.php

The Signal Margin of a channel on a rabbitears.info report is similar to the Noise Margin on a TVFool report.

Since you are not able to post an active link until you have more than 5 posts, just give us the ID number of the report.
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If you can not measure it, you can not improve it.
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www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 03-01-2020 at 05:14 PM.
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post #5 of 13 Old 03-01-2020, 05:52 PM - Thread Starter
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WOWZA! You guys ROCK: Thank you for the rapid, comprehensive reply; I am clearly in good hands here! Rat, I use the 622 for both sat and OTA. OTA is really only used for KING5 and KIRO7.
So, my RabbitEars report is (removed by order of site) and this install is circa 2006.
It has been effing up in this manner since day one. I more or less gave up on OTA back then, paying for locals via Dish Network, ever since. These days, I only watch an hour and a half of local + national news, and am really tired of paying $70.00 month for 900 channels of BS that I NEVER watch! The 4228 is mounted outside, on a mast that is bolted to standoffs which are themselves bolted to the fascia board at the roof level of my two story house. The bow-ties on the antenna are all rusted (does rust significantly attenuate the signal?) but the rg6 is in great condition. I tried bypassing the grounding block, which made virtually NO difference. The two obvious concerns are; 1) there is some slop in the gears of my Eagle Aspen rotator, allowing me to easily wiggle the antenna's aim, if only by perhaps two degrees of rotation, and 2) a stand of five Evergreen trees, perhaps 70 to 100 feet tall, at a distance ranging from 300 to 400 feet from the antenna bearing, 295 to 300 degrees magnetic (no correction for mag variation). The thing is, the signal strength drops at random. I will be watching our NBC affiliate KING5 for an hour or more without interruption, then, here we go again. Rain, shine, windy, calm, cold, hot, whatever...the signal strength meter will suddenly just drop all the way down to zero for a few seconds, or a minute, or longer. WTF????? I realize that when signal strength drops below a certain threshold, the image freezes/pixelizes/switches over to captain obvious graphics saying "re-acquiring signal", but from 70% all the way down to 0% in one or two seconds? Really? To me, that does not sound like foliage of a tree momentarily blocking the signal, nor a slight movement of the antenna, nor airplanes causing multipath. To me, that sounds like an intermittent open or short at a coax connection, or even the preamp intermittently cutting out!. Cal, I will PM Don.
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post #6 of 13 Old 03-01-2020, 06:09 PM - Thread Starter
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I guess I cannot even PM anyone until I have fifteen posts, sigh. Anyway, my Rabbit Ears result&study_id=65254. Thanks anyway Cal.
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post #7 of 13 Old 03-01-2020, 07:22 PM
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Thank you for the ID number; here is the report:
https://www.rabbitears.info/searchma...study_id=65254

It does sound like an intermittent connection.

Quote:
Originally Posted by Starlifter-f/e View Post
I use the 622 for both sat and OTA. OTA is really only used for KING5 and KIRO7......this install is circa 2006. It has been effing up in this manner since day one....The bow-ties on the antenna are all rusted (does rust significantly attenuate the signal?.....there is some slop in the gears of my Eagle Aspen rotator.....
A few things you might try:

Do you still have the problem if you use a TV tuner instead of the 622 tuner for OTA?

IIRC, doesn't the rotator use the same coax for motor control and signals? I wonder what would happen if you ran a good length of coax directly from the antenna to a tuner.

Rust on the whiskers shouldn't hurt, but the connection between the whiskers and the vertical phase lines might be bad. However, you said you had the problem right from the start.

The balun could be bad.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html
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post #8 of 13 Old 03-02-2020, 03:52 AM
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The problem also has the symptoms of multipath.



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
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post #9 of 13 Old 03-02-2020, 08:02 AM
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You didn't say if the drop to zero occurs on all channels at the same time. If it does then an intermittent connection is most likely. Fourteen years is a pretty good run for a consumer antenna in a wet environment. A rusty antenna is at the end of its life. I'd replace it.

Your Rabbitears report would indicate you don't need a preamp, especially not one with 30 dB of gain. If you have multiple TVs then a distribution amp might be in order.
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post #10 of 13 Old 03-02-2020, 09:33 PM - Thread Starter
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Balun?

OK, Rabbit. First, what is a balun? What does it look like, what does it do, and if I don't have one, would that result in an intermittent signal loss or a steady-state complete signal loss? I apologize for the stupid questions. I will try scrubbing the rust of all of the bowties (whiskers?). I already use a separate coax cable from the rotator to it's control box to prevent any signal loss from the antenna.

Cal, I will try taking the preamp out of the signal path. If scouring the rust off the bowties and removing the preamp do not work, would you recommend a new 4228HD, or a DB8e? I do not want a Yagi.

Rat, I understand you cannot fight multipath. I cannot move the antenna anywhere else on the property, although I am extending the mast to get an additional eight feet, and installing guy wires to prevent wind deflection. I doubt the wind has anything to do with this since it happens with and without wind. I am about 20 miles south of SeaTac airport's approach path, but I cannot see how multipath reflecting from an airliner could cause a complete signal loss for a minute or more when traveling at 200 knots...

Thank you all for your kindness and support. I really do feel welcome and I appreciate your wealth of expertise!
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post #11 of 13 Old 03-03-2020, 03:54 AM
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Quote:
Originally Posted by Starlifter-f/e View Post
OK, Rabbit. First, what is a balun?
https://www.parts-express.com/parts-...xoCF0YQAvD_BwE


Airplanes are not the only cause of multipath. Big trees should be considered as well as buildings, metal (roofs, alum. siding, etc.)



If you can’t explain it simply, you don’t understand it well enough – Albert Einstein
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post #12 of 13 Old 03-03-2020, 07:35 AM
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Quote:
Originally Posted by Starlifter-f/e View Post
OK, Rabbit. First, what is a balun? What does it look like, what does it do, and if I don't have one, would that result in an intermittent signal loss or a steady-state complete signal loss? I apologize for the stupid questions.
It's not a stupid question; it's an intelligent question. I will try to give an intelligent answer.

The term balun is short for BALanced to UNbalanced. As Ratman showed you in his link to a balun, it is a matching transformer that connects the 300 ohm balanced terminals of your antenna to the 75 ohm unbalanced coax. Balanced means that neither terminal is connected to ground; unbalanced means one terminal is grounded.

You said you had the old original CM4228 antenna, which looks like this:

http://www.hdtvprimer.com/ANTENNAS/cm4228.html





I measured the loss of 3 different baluns:



Since two baluns were connected in series for measurement, the loss of one balun is 1/2:



The loss of the new 94444 seemed high, so I cut the leads to 2-1/2". The long leads were creating a transmission line of indefinite impedance with increased loss.





The new 4228HD uses a PCB (printed circuit board) balun that is an integal part of the antenna.
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Last edited by rabbit73; 03-06-2020 at 07:50 AM.
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post #13 of 13 Old 03-03-2020, 11:26 AM
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Quote:
Originally Posted by Starlifter-f/e View Post
Rat, I understand you cannot fight multipath. I cannot move the antenna anywhere else on the property, although I am extending the mast to get an additional eight feet, and installing guy wires to prevent wind deflection. I doubt the wind has anything to do with this since it happens with and without wind. I am about 20 miles south of SeaTac airport's approach path, but I cannot see how multipath reflecting from an airliner could cause a complete signal loss for a minute or more when traveling at 200 knots...
There are two types of multipath, static and dynamic. Static multipath involves stationary objects; dynamic involves moving objects, like aircraft. Your antenna can receive the direct signal from the transmitter and a signal reflected off aircraft. The reflected signal can either help or hinder the direct signal depending upon the phase relationship between the two signals.

I have no idea if your problem is caused by multipath, but your location is in the SeaTac flight patterns, and the flight patterns are in the signal paths from the north.









https://www.portseattle.org/projects/flight-patterns

There are two experiments that are worth trying. The first is to attenuate the TV signals to eliminate the possibility of overload, by removing the preamp and inserting attenuators to find out how weak they can be before they all dropout. I would hope that you have some kind of relative signal strength indicator in your reception equipment.

The second experiment is to try a different tuner connected to your antenna, like a recent TV tuner. Your 622 tuner design is probably almost 15 years old. At the time of the transition from analog to digital TV, the best tuners were in the converter boxes because they had to meet government specs for the coupon program. Later, the TV tuners were improved. The most important improvement was in the ability to handle multipath problems; the 5th generation tuners were about as good as they can be.

There are indications that the new ATSC 3.0 standard will be better able to handle multipath than the current ATSC 1.0 standard for digital TV.

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If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html

Last edited by rabbit73; 03-06-2020 at 07:50 AM.
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