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Old 31-Mar-2013, 6:11 AM   #21
rabbit73
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Ynot713:

Your equipment is acting in a way that is normal and to be expected.

Your problem is overload. If you look at your tvfool report you will see that the signal power for WFXV is -10.4 dBm. It is highlighted in red to indicate the possibility of overload in a preamp or tuner. I quote from tvfool Signal Analysis FAQ:
Quote:
NOTE 2: If you live very close to some transmitters, you might see a few of the values in the "Pwr(dBm)" column highlighted in red if power levels get a bit high. This is a warning that such high power levels might be enough to cause overload problems on some amps and receivers if you're not careful.
THREE TYPES OF OVERLOAD

There are three types of preamp or tuner overload, in order of increasing signal strength:

1. The strong signals almost cause enough IM distortion to interfere with the reception of weak desired signals, but the spurious signals are at or below the noise floor. This is the point that holl_ands uses in his preamp charts to obtain max SFDR (Spurious Free Dynamic Range). No damage will happen. A preamp chart by him is here:
http://imageevent.com/holl_ands/files/ota

Click on Modified solidsignal Chart Comparing Preamps - RevA

His chart shows the max input for various preamps that will give best SFDR. Most tuners will tolerate a -10.4 dBm signal, but if you look at the chart you will see that it is too strong for ANY of the preamps listed.

As the strongest signals continue to increase in strength, more of the weaker signals are damaged until you reach:

2. The strong signals cause overload to the preamp or tuner that makes it impossible to receive any signals. No damage will happen.

3. The signals are so strong that the input transistor is toast. You are not likely to encounter OTA signals that strong.

TUNER SPECIFICATIONS

If you look at the tuner specifications you will see that there are limits to what they can handle in the way of signal stength:

ATSC Recommended Practice:
Receiver Performance Guidelines
Document A/74:2010, 7 April 2010
http://www.atsc.org/cms/standards/a_74-2010.pdf

scroll down to page 12:
RECEIVER PERFORMANCE GUIDELINES

5.1 Sensitivity
A DTV receiver should achieve a bit error rate in the transport stream of no worse than 3x10-6 for input RF signal levels directly to the tuner from –83 dBm to –5 dBm for both the VHF and UHF bands.

5.2 Multi-Signal Overload
The DTV receiver should accommodate more than one undesired, high-level, NSTC or DTV signal at its input, received from transmission facilities that are in close proximity to one another. For purposes of this guideline, it should be assumed that multiple signals, each approaching –8 dBm, will exist at the input of the receiver.

As you can see, WFXV is about right at the overload point without preamp gain, taking into consideration the antenna gain is added and the coax loss is subtracted from that -10.4 dBm figure.

WHY YOU GOT THE RESULTS YOU DID

So, your question is why did the antenna and preamp inside the attic give you the channels that you wanted, but the antenna and preamp outside didn't?

The answer is that when the antenna and preamp were in the attic, there was sufficient attenuation of the signal by the attic construction to prevent overload of the preamp or tuner. But when the antenna and preamp were outside, you didn't receive any signals at all because of the type 2 overload mentioned above.

TVPRAMP1R SPECIFICATIONS

These are the specs for the TVPRAMP1R. As you can see, when you add the preamp gain to the -10.4 dBm figure, overload is certain.

Designed specifically to improve the performance of outdoor antennas in low signal strength areas
Gain: VHF: 16 dB; UHF: 22 dB
Separate or combined inputs for UHF/VHF
Switchable FM trap reduces interference from FM frequencies
Separate amplification for UHF & VHF bands to improve performance
You can use the 1296F as a variable attenuator to control the dB Gain

WHAT HAPPENED IN THE BASEMENT AND ATTIC

When you ran the coax directly from the outside antenna down to the basement TV there was sufficient signal strength to receive the local signals, but you were missing amplification to receive the weaker signals.

The attic setup (and in your living room with Monoprice antenna and its 20 dB amp) were able to achieve that happy compromise of not enough signal to cause overload, but enough preamp gain to receive the weaker signals. This is what holl_ands is talking about in type 1. overload mentioned above for maximum SFDR. The dynamic range that you need to accomodate is -10.4 dBm for WFXV to -50.9 dBm for WCBT, which is 40.5 dB. If you want even weaker signals, the dynamic range will be even greater.

WHAT YOU CAN DO

In order to duplicate the results of the previous attic antenna you can try the 751 and preamp up there. If the 751 is outside, then you will need to run your coax directly down to the basement and put a preamp there wth an attenuator just before it to simulate the attic loss. The attenuator should be adjusted to make the strongest signals just weak enough to prevent overload. If your TV has a signal strength meter, it would help with the adjustments.
attenuator

Because you are in a strong signal location the coax for the outside antenna should be grounded with a grounding block to prevent direct pickup by the TV and so the quad shield isn't wasted. The grounding block and the mast should be connected to the house electrical system ground with no. 10 copper wires to comply with NEC requirements.

Once you have achieved that, then your distribution system should be designed to maintain that balance by making the signal stronger for the longer coax runs and weaker for the short coax runs. You can do that with a cascade arrangement of 2-way splitters.

A MORE ACCURATE TVFOOL REPORT WOULD BE HELPFUL

Because you are so close to the local transmitters, it would be useful if we could see a more exact tvfool report for your location.
Quote:
WARNING: Address was only resolved to block level and might not be that close to your actual location. For more accurate results, try entering a specific address or coordinates.
If you use the interactive map feature you can move the marker to your exact location (left click on marker and hold down, move x to spot and release) and then produce a report by clicking at the upper right of the map. It's fun to watch the coordinates change as you move the marker. Don't forget to enter the antenna height below the map.
http://www.tvfool.com/?option=com_wrapper&Itemid=90
Attached Images
File Type: jpg holl_ands preamp chart.JPG (187.0 KB, 218 views)
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Last edited by rabbit73; 10-Apr-2013 at 12:38 AM.
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Old 31-Mar-2013, 7:34 AM   #22
rabbit73
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Pete Higgins is using a drop amp (like CM3410) instead of a preamp. He lives in a strong signal area and claims that it is more resistant to overload.

Signal Amplifiers (Amps, Preamps, Distro Amps)page 221
http://www.digitalhome.ca/forum/show...42426&page=221
posts 3304, 3313

page 222
http://www.digitalhome.ca/forum/show...42426&page=222
posts 3321, 3327, 3330

page 223
http://www.digitalhome.ca/forum/show...42426&page=223
posts 3332, 3334, 3336, 3338

Last edited by rabbit73; 2-Apr-2013 at 1:34 AM.
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Old 2-Apr-2013, 1:30 AM   #23
rabbit73
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I took another look at Pete Higgins posts to find out how strong his local signals are; his tvfool report looks like this:
http://www.tvfool.com/?option=com_wr...1dda169109ca5c

His strongest signal is KVCR at -15.6 dBm, which is not quite as strong as your -10.4 dBm signal, but it was giving him trouble with overloaded preamps that he needed for his weaker signals, much like your problem.

ADTech posted some spectrum analyzer images that compare two CM amps and one AD preamp that seem to confirm that a drop amp can handle stronger signals than a preamp:
http://www.digitalhome.ca/forum/show...postcount=3285

Last edited by rabbit73; 2-Apr-2013 at 1:35 AM.
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Old 2-Apr-2013, 2:03 AM   #24
teleview
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Yes drop amps and distribution amps are more resistant to overload then a preamp.

That is true.

And is a interesting point.

However.

The ANT751 antenna is to small for the job of receiving the Very Weak Tv transmissions at the bottom of the 'receivable' tv stations list.

The way to Avoid Any Type or Kind of Amplifier Overload is Not Use a amplifier of any type or kind.

To do that , use a Bigger antenna , As In , Bigger Antenna.

Not somewhat bigger , but , --> Bigger as in Bigger.

A Bigger Antenna Will Receive More Signal , receiving more signal , means Stronger Signal Strength in the antenna system.

Stronger Signal Strength delivered from the antenna , Can mean no amplifier required.

If No Amplifier is used then the amplifier will not be overloaded because there is no amplifier.

Last edited by teleview; 3-Apr-2013 at 9:27 PM.
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Old 2-Apr-2013, 2:17 AM   #25
No static at all
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Quote:
Originally Posted by rabbit73 View Post
. . . .a drop amp can handle stronger signals than a preamp
Absolutely!! The Channel Master drop amps are much more tolerant of strong signals than the benchmark Winegard HDP-269 preamp. It would certainly be worth a try for the OP to retain the desired weaker signals if the passive splitter scenario doesn't pan out.
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Old 2-Apr-2013, 5:48 AM   #26
Ynot713
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Thank You everyone for your assistance. Rabbit73, thanks for explaining everything like that. I finally feel like I have a grasp as to what is going on. I'm trying to understand some of the charts that were linked but am finding myself in a state of confusion with all the numbers as it is way above my level of expertise.

I guess my next two steps are to try the amp in the basement w/ the passive splitter and if that dosent work, try the CM-3418 DISTRIBUTION AMPLIFIER - 8 PORT with no preamp.

I have the antenna run w/ no preamp right now and am getting decent signal, but still running into issues with those weaker signals that I really want to get. Besides that, my local news station (WKTV) which is not in the direction of my antenna but 11mi or so away at 120 deg, is not coming in at all.

I know bigger, bigger antenna. That will be my last resort. I bought this antenna because it was discrete, clearly I should have sought all of your insight prior to going through all the work of mounting it.

Thank you all and, I'f you'd like I'll continue to update you on my status as I try different options.

One other question, and I'm sure this is a completely dumb amateur question, but what if I turned my antenna around to face the Albany towers, with the preamp? Like 135 degreeish? Would that lower the signal enough to use the preamp and possibly receive towers from Albany and Syracuse? Like I said, amateur question but I was just curious. Please try not to start your response to this with, "Yes that was a completely dumb amateur question."

Thanks Again.
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Old 2-Apr-2013, 7:08 AM   #27
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"Yes that was a completely dumb amateur question.".... NOT!

You've articulated an effective method of balancing signal levels in select situations. By turning the Antenna 180 from a signal source it will still receive, but at a lower level. That can help in some situations such as when you have powerful signals opposite weak signals.
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Old 3-Apr-2013, 8:57 PM   #28
Ynot713
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Quote:
Originally Posted by GroundUrMast View Post
"Yes that was a completely dumb amateur question.".... NOT!

You've articulated an effective method of balancing signal levels in select situations. By turning the Antenna 180 from a signal source it will still receive, but at a lower level. That can help in some situations such as when you have powerful signals opposite weak signals.
Thanks for making me feel like I somewhat know what I'm talking about lol. Now the question is....Do you think that could work given my particular situation?
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Old 3-Apr-2013, 10:29 PM   #29
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The ANT-751 is rather small when chasing after the Albany signals. But you have it, so if you're comfortable working on your roof, it's a very simple experiment to turn the antenna to point the other way.

If you can keep the test simple by connecting only the antenna and a single TV, you'll eliminate questions re. the integrity of components that could be causing some of the other problems you've been troubleshooting. Again, be sure to rescan the TV when you make a change to the system (new antenna, aim-point, add or remove a component, etc.).
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Old 5-Apr-2013, 12:14 AM   #30
Ynot713
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It worked! Antenna at 135 deg with RCA Preamp at antenna and I get Albany's Fox, CBS and NBC among others. No overload and I still get all of the Syracuse stations I got before and all of my local stations!

I am actually getting 28 stations now which is more that I got before.

Thank you to everyone for all your help! I really appreciate it. I can only imagine what I could get with a bigger antenna. I love living on top of a hill.

As the weather gets warmer, now I have to start thinking about grounding this thing.
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Old 5-Apr-2013, 12:56 AM   #31
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Thanks for letting us know how the 'test' turned out. That's very good to hear.

This tends to confirm the theory that you're in a narrow window of strong versus weak signal reception and that just a minor change in any one of the major components would tip the scale one way or the other.

I still have very little affection for the RCA preamp in this application, but if this current arrangement works, great (don't fix it if it aint broke).

Grounding is a good idea, and it rarely needs to be a big expensive project.
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