Help in S.E.Va.

[JET4]

Have a single story brick ranch house.Put a Channel Master CM-4221HD antenna in the attic.Get about 30 channels but the two channels my wife wants are QVC (49.5) and HSN (49.6). They don"t come in good at all. Would a better antenna do the job or do I have to move the antenna I have outside? Prefer to keep antenna in attic but will move outside if it will be better.Will get a different antenna if it" better. Thanks for your help.
http://www.tvfool.com/?option=com_wr...dfaf9632dd6b09

[rabbit73]

Welcome, JET4:

What direction is you antenna aimed?

Do you get ION 49.1 OK?

Your signals are very strong to the point of overload. The signal loss in the attic is difficult to predict because of differences in construction, but if your attic is average the 4221HD might have enough gain to cause overload.

A metal roof, aluminum foil thermal barrier, and aluminum, siding will block TV signals, as will trees or other buildings.

Are you using an amp?

To test the overload theory, insert an attenuator in the coax line. A 2-way splitter has a loss of 3.5dB; a 4 way, 7 dB. You might need even more attenuation than that.

For your location I would have picked the GE 34792 Attic antenna. I just assembled one for a friend in Newport News and he is using it inside on the first floor. He gets the channels you want OK

How long is the coax line from the antenna to the TV?

[JET4]

antenna aimed about 260 degrees on compass. wsw. ION 49.1 comes in good

[JET4]

no amp. new roof was just put on regular shingles. I can get GE attic antenna if it will be better

[rabbit73]

WPXV is 258 degrees magnetic by compass.

If you get ION OK, then you should be getting QVC and HSN OK because they are all on the same channel. Try slightly different locations in the attic and an attenuator. Keep adding more attenuation to see what happens. Does your TV have a signal strength indicator?

[rabbit73]

I can get GE attic antenna if it will be better

I can't guarantee that it will be better because I'm not 100% certain yet what the problem is. Let's try some attenuation first with the antenna you have.

This is my friend's report; your signals are 10 dB stronger.

http://www.tvfool.com/?option=com_wr...dfafa556f19277

This is the attenuator I used when testing his antenna. I was able to insert the full 20 dB attenuation for his strongest signals without them dropping out. CH 13 was a little weaker because the GE antenna has less gain for VHF-High signals.

https://www.antennasdirect.com/store...ttenuator.html

Also here
https://www.walmart.com/ip/Antennas-...uator/43160862

I bought mine here:

http://www.solidsignal.com/pview.asp?p=att-1

The knob on the attenuator works like a volume control with multiple turns. Turn it clockwise to make the signal stronger (less attenuation).

The GE 34792 is on sale at Walmart for $26.47 but requires some assembly. There is a video for that.

https://www.youtube.com/watch?v=1qYucg3JXzA

[JET4]

coax line,antenna to tv about 20'

[rabbit73]

If it isn't overload, then it must be trees. I don't know your exact address, but I see a lot of trees in your area. Trees block TV signals.
http://www.hdtvprimer.com/antennas/siting.html
scroll down to Trees and UHF

The only other thing I can think of is interference to TV reception from your strong local FM signals.
http://www.fmfool.com/modeling/tmp/6...e/Radar-FM.png

Please let us know the results of your tests on this same thread.

[WIRELESS ENGINEER]

Since most TVs deal with cable signal levels of 0 to
+15 db without issue, I don't think this is an overload issue
If you get the other 49 channels then there is no reason
You ma be getting co channel interference though the map doesn't show it

[JET4]

I ordered the attenuator that you used to check everything out.Will let you know when it's here and I tested it. Also a lot of trees between my house and the towers. The street in front of my house looks like a forest. Lol.

[rabbit73]

Originally Posted by WIRELESS ENGINEER

If you get the other 49 channels then there is no reason

I agree. If you get 49.1, you should be getting 49.5 and 49.6.

Since most TVs deal with cable signal levels of 0 to +15 db without issue, I don't think this is an overload issue

You haven't stated the units, but you probably mean dBmV.

Yes, that is a good range for the input at the tuner, but his signals on his report are much stronger than that. The tvfool report assumes that the antenna is outside and in the clear. His antenna is in the attic and many trees are in the signal path. Now that he has told us about the trees (and I have seen the trees in a satellite view of his area), I am beginning to think it might NOT be an overload problem.

WHRO has a Noise Margin of 71.4 dB. If you add an antenna gain of 12 dB, that brings you up to 83.4 dB NM which is overload territory IF the antenna is outside and in the clear. But, his antenna is in the attic and there are trees in the signal path that can attenuate the signals.



Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html

WHRO has a signal power of -19.4 dBm (+29.6 dBmV). If you add the antenna gain, that brings you up to -7.4 dBm (+41.6 dBmV) which is tuner overload.

ATSC Recommended Practice:
Receiver Performance Guidelines

Document A/74:2010, 7 April 2010

RECEIVER PERFORMANCE GUIDELINES

5.1 Sensitivity

A DTV receiver should achieve a bit error rate in the transport stream of no worse than 3x10E-6 (i.e., the FCC Advisory Committee on Advanced Television Service, ACATS, Threshold of Visibility, TOV) 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.

When there are more than Two Strong Input Signals:
Max Signal Input would need to be DERATED:
3 Signals: -3.6 dB
4 Signals: -5 dB
5 Signals: -6 dB
6 Signals: -7 dB
8 Signals: -8 dB
Ignore signals more than 6 dB below the Strongest.

In this case, signals stronger than -16 dBm (+33 dBmV) risk tuner overload. I have no idea how strong the signals are coming out of the 4221HD antenna in the attic, because the attenuation from the trees and the attic are unknown.

[rabbit73]

Originally Posted by JET4

no amp. new roof was just put on regular shingles.

Were you using the attic antenna before the new roof? If you were, was there any change in reception after the new roof?

If the attenuator doesn't help, I suggest you try a preamp that is resistant to overload since the attenuation from the trees and the attic might be more than we thought.

For preamps consider the Channel Master 7778, the Antennas Direct Juice with an FM filter added, or the RCA TVPRAMP1R. The CM and the RCA have internal FM filters. The AD Juice does not have an internal FM filter, but it does have a 4G-LTE filter to reject cell phone transmissions. The RCA is inexpensive, but has a history of quality control problems.

Attic antennas are not required to be grounded, but it would be a good idea to ground the coax shield with a grounding block to reject interference from strong local FM signals.
http://www.fmfool.com/modeling/tmp/6...e/Radar-FM.png

[JET4]

Once I get the attenuator I will report back. This is about to get over my head. Lol. I though I could just get rid of cable TV and install a antenna.We'll see what happens. Thanks

[rabbit73]

Yes, it can get complicated, especially with an attic antenna and trees. It is going to take a few tests, and the results of those tests will determine what to try next. You are doing fine and we will try to help you as best we can in this "remote control" way.

If you are willing to give me your address in a Private Message, I can see what the trees look like in an aerial view and add the green signal lines. It would look something like this:

Vertical view:



Bird's eye view:




You can do your own using the tvfool interactive map browser by moving the cursor (drag and drop) to your antenna location.
http://www.tvfool.com/index.php?opti...pper&Itemid=90

Do you get WVEC 13 ABC OK?

[ADTech]

If you get 49.1-49.4 just fine (or as fine as you can for standard def programming), there's absolutely nothing wrong with your antenna. Leave it alone, otherwise you may break something that isn't yet broken.

[rabbit73]

ADTech's comment reminded me of a problem that I had with a converter box and ION, and so did others. It seemed to be a problem with the network feed, because after a while it cleared up. It is hard for me to believe that the Apex boxes healed themselves.
http://www.highdefforum.com/local-hd...onalities.html

ION must have had reports of the problem because they suggested a double rescan:

http://www.iontelevision.com/rescan

What equipment are you using for reception?

Do you have more than one TV to try with the antenna?

[WIRELESS ENGINEER]

EXCELLENT information as usual rabbit

Nice work!

[rabbit73]

Thank you; I keep trying.

Sometimes I get a hit and sometimes I strike out.

[JET4]

Well the attenuator came in today and I installed it . Did not see any improvement at all. I turned it all the way up and put it on channels 49.5 and 49.6 and they were the same. Started backing the knob down a litltle at a time and saw no change. Should I try the preamp now ? I can move the antenna outside if it will make it much better. I have a 20' pole on the side of my house where I had a antenna many years ago. If I move the antenna outside it may take a while as at the monment I have one hand.(have a bad tendon in left hand). I'll have to get my son-in-law over one day to help. Let me Know my next step. Thank you

[rabbit73]

Thanks for making the test and giving us the report.

Started backing the knob down a litltle at a time and saw no change.

If you were using the AD ATT-1 attenuator, you should have seen channels getting worse as you turned it down. It can turn down about 3-3/4 turns.

You didn't answer this question:

Were you using the attic antenna before the new roof? If you were, was there any change in reception after the new roof?

What equipment are you using for reception? How many TVs do you have?

Have you tried another TV with the antenna?

Have you tried a double rescan to clear the tuner memory?
https://www.google.com/#q=FCC+double+rescan

When all of those are checked, then it is time to try a preamp.