OTA Question

[hd4me2]

I am having a low signal problem on most of my HDTV OTA channels. I tried a CM indoor 13 dB amplifier, NF is 3.5 dB as I recall, and lost all channels. Is this telling me that my S/N is < 3.5 so that when the amplifier is used it drives my signal into the noise due to the 3.5 dB NF? If this is true then probably a pre-amp wouldn't work either since their NF are only slightly better; right?

If a pre-amp or amp won't help then I guess the only thing I can do is optimize the antenna pointing as much as possible, I haven't tried tilting the beam up in elevation or raising the antenna any higher.

Any suggestions, comments, etc. would be much appreciated.

[LeeS]

What's your zipcode?

Or better yet, cut and paste the results you get from www.antennaweb.org. Click on 'digital stations only' Use your full address, answer all the questions.

We'll go from there :)
Lee

[hd4me2]

If I choose digital only I only get one very local station to show up. As you can see I live about equal distance, about 40 miles, from the D.C. and Baltimore transmit sites. The terrain is hilly with lots of big trees. I pointed the CM 4228 to 122 deg. magnetic to try and capture the Baltimore major networks, channels 11, 13, 2 and 45.

When aimed at 122 deg. I received signal strengths readings on my Samsung SIR-TS160 as follows:

ch 2 63% Balt
4 20% DC
5 30% DC
7 30 to 36% DC
9 69% DC
11 30 to 36% Balt
13 69% Balt
45 69%
67 69% Balt

As you can see some of the DC stations are stronger than the Baltimore stations, must have a decent sidelobe in the DC direction. Thanks for any help or suggestions you can provide.


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Stations

Address Location Results
The address you entered was located at the Street level.



Stations and Antenna Types
TV reception is determined by the size and type of antenna and the direction in which it is pointed. To determine the right antenna, use the color coded Antenna Type to select the channels that you wish to view. Antenna types are color coded according to the size and type of antenna needed for reception. The list is arranged in order of ease of reception, with the stations requiring the smallest multidirectional antenna at the top, to those requiring the largest directional antennas at the bottom.

Use the "Compass Orientation" listed below to point your antenna or rotor system for the channels you wish to receive. Please note that "Compass Orientation" is referenced to magnetic North.





Show All Stations Show Digital Stations Only Show Analog Stations Only



DTV Antenna
Type Call Sign Channel Network City State Live
Date Compass
Orientation Miles
From Frequency
Assignment
red - uhf WFPT 62 PBS FREDERICK MD 199° 16.6 62
* blue - uhf WFPT-DT 28 PBS Frederick MD TBD 192° 19.0 28
violet - vhf WGAL 8 NBC LANCASTER PA 56° 49.9 8
violet - uhf WGCB 49 IND RED LION PA 66° 45.8 49
violet - uhf WHAG 25 NBC HAGERSTOWN MD 295° 36.5 25
violet - uhf WETA 26 PBS WASHINGTON DC 176° 40.8 26
violet - uhf WJAL 68 IND HAGERSTOWN MD 315° 43.2 68
violet - vhf WJLA 7 ABC WASHINGTON DC 174° 42.1 7
violet - uhf WHP 21 CBS HARRISBURG PA 32° 60.4 21
violet - uhf WDCA 20 UPN WASHINGTON DC 176° 40.8 20
violet - vhf WBAL 11 NBC BALTIMORE MD 122° 37.2 11
violet - uhf WBFF 45 FOX BALTIMORE MD 122° 37.3 45
violet - uhf WBDC 50 WB WASHINGTON DC 170° 42.2 50
violet - uhf W35BT 35 FMN Harrisburg PA 26° 55.4 35
violet - vhf WUSA 9 CBS WASHINGTON DC 174° 42.1 9
violet - uhf WUTB 24 UPN BALTIMORE MD 131° 33.4 24
violet - uhf WVPY 42 PBS FRONT ROYAL VA 245° 68.2 42
violet - uhf WWPB 31 PBS HAGERSTOWN MD 293° 36.7 31
violet - uhf WPMT 43 FOX YORK PA 58° 50.3 43
violet - uhf WPXW 66 PAX MANASSAS VA 192° 51.7 66
violet - uhf WFDC 14 TFA ARLINGTON VA 175° 42.8 14
violet - vhf WTTG 5 FOX WASHINGTON DC 174° 41.7 5
violet - vhf WRC 4 NBC WASHINGTON DC 175° 42.8 4
violet - uhf WNUV 54 WB BALTIMORE MD 131° 33.4 54
violet - uhf WNVC 56 IND FAIRFAX VA 185° 45.9 56
violet - vhf WJZ 13 CBS BALTIMORE MD 122° 37.2 13
violet - uhf WLYH 15 UPN LANCASTER PA 51° 66.9 15
violet - vhf WHSV 3 ABC HARRISONBURG VA 239° 96.3 3
violet - uhf WHTM 27 ABC HARRISBURG PA 29° 57.0 27
violet - uhf WHUT 32 PBS WASHINGTON DC 176° 40.8 32
violet - uhf WITF 33 PBS HARRISBURG PA 32° 60.5 33
violet - vhf WMAR 2 ABC BALTIMORE MD 122° 37.3 2
violet - uhf WMPB 67 PBS BALTIMORE MD 112° 28.5 67
violet - uhf WMPT 22 PBS ANNAPOLIS MD 145° 51.8 22
Note:
The above listing is a conservative prediction of stations received. Depending on the specifics of your installation, you may be able to receive stations that do not appear in this list.

DTV Antenna
Type Call Sign Channel Network City State Live
Date Compass
Orientation Miles
From Frequency
Assignment
red - uhf WFPT 62 PBS FREDERICK MD 199° 16.6 62
violet - vhf WGAL 8 NBC LANCASTER PA 56° 49.9 8
violet - uhf WGCB 49 IND RED LION PA 66° 45.8 49
violet - uhf WHAG 25 NBC HAGERSTOWN MD 295° 36.5 25
violet - uhf WETA 26 PBS WASHINGTON DC 176° 40.8 26
violet - uhf WJAL 68 IND HAGERSTOWN MD 315° 43.2 68
violet - vhf WJLA 7 ABC WASHINGTON DC 174° 42.1 7
violet - uhf WHP 21 CBS HARRISBURG PA 32° 60.4 21
violet - uhf WDCA 20 UPN WASHINGTON DC 176° 40.8 20
violet - vhf WBAL 11 NBC BALTIMORE MD 122° 37.2 11
violet - uhf WBFF 45 FOX BALTIMORE MD 122° 37.3 45
violet - uhf WBDC 50 WB WASHINGTON DC 170° 42.2 50
violet - uhf W35BT 35 FMN Harrisburg PA 26° 55.4 35
violet - vhf WUSA 9 CBS WASHINGTON DC 174° 42.1 9
violet - uhf WUTB 24 UPN BALTIMORE MD 131° 33.4 24
violet - uhf WVPY 42 PBS FRONT ROYAL VA 245° 68.2 42
violet - uhf WWPB 31 PBS HAGERSTOWN MD 293° 36.7 31
violet - uhf WPMT 43 FOX YORK PA 58° 50.3 43
violet - uhf WPXW 66 PAX MANASSAS VA 192° 51.7 66
violet - uhf WFDC 14 TFA ARLINGTON VA 175° 42.8 14
violet - vhf WTTG 5 FOX WASHINGTON DC 174° 41.7 5
violet - vhf WRC 4 NBC WASHINGTON DC 175° 42.8 4
violet - uhf WNUV 54 WB BALTIMORE MD 131° 33.4 54
violet - uhf WNVC 56 IND FAIRFAX VA 185° 45.9 56
violet - vhf WJZ 13 CBS BALTIMORE MD 122° 37.2 13
violet - uhf WLYH 15 UPN LANCASTER PA 51° 66.9 15
violet - vhf WHSV 3 ABC HARRISONBURG VA 239° 96.3 3
violet - uhf WHTM 27 ABC HARRISBURG PA 29° 57.0 27
violet - uhf WHUT 32 PBS WASHINGTON DC 176° 40.8 32
violet - uhf WITF 33 PBS HARRISBURG PA 32° 60.5 33
violet - vhf WMAR 2 ABC BALTIMORE MD 122° 37.3 2
violet - uhf WMPB 67 PBS BALTIMORE MD 112° 28.5 67
violet - uhf WMPT 22 PBS ANNAPOLIS MD 145° 51.8 22
Note:
The above listing is a conservative prediction of stations received. Depending on the specifics of your installation, you may be able to receive stations that do not appear in this list.

DTV Antenna
Type Call Sign Channel Network City State Live
Date Compass
Orientation Miles
From Frequency
Assignment
* blue - uhf WFPT-DT 28 PBS Frederick MD TBD 192° 19.0 28
Note:
The above listing is a conservative prediction of stations received. Depending on the specifics of your installation, you may be able to receive stations that do not appear in this list.


© Copyright CEA 2004

[LeeS]

I agree, the only digital station in all those listings is WFPT-DT in Federick.

The 4228 is UHF only but might pickup stations in the High VHF band (channels 9-13).

An RF amplifier should be mounted as close to the antenna as possible to eliminate picking up and amplifying noise.

From the results you posted it looks like all you are getting is analog stations, with the exception of WFPT.

www.antennaweb.org is usually pretty accurate. Maybe give the major network stations in your area a call or check their websites to see if they are transmitting a digital signal.

From what you cut/pasted, your DTV outlook looks pretty bleak. :(

Lee

[Ratman]

I'm pretty sure that the DC/Balt area has a quite a few digital stations. Something is amiss...

I'd say your biggest obstacle is being indoors. If you can't get an antenna on the roof, then try the attic.

Secondly, you'll probably need a rotor to get both DC and Balt channels.

[hd4me2]

All the Channels I listed are digital, I should have used the corresponding UHF channel # not the corresponding local VHF #.

ch 2 63% Balt UHF 52
4 20% DC UHF 48
5 30% DC UHF 36
7 30 to 36% DC UHF 39
9 69% DC UHF 34
11 30 to 36% Balt UHF 59
13 69% Balt UHF 38
45 69% UHF 45
67 69% Balt UHF 67
I e-mailed CM and they thought if the analog UHF channels were just weak and not ghosty that a 7775 pre-amp, that has a 2.0 NF, might work. Although I've only got 50 ft of coax that's still 2.5 to 3.0 dB of loss. Maybe with a good pre-amp at the antenna my signal strength might improve. What do you think.

Thanks

[Splicer]

Don't 4get that an amplifier that is for VHF will not boost anything that is UHF and vice-versa. :smokin:

[Ratman]

Although I've only got 50 ft of coax that's still 2.5 to 3.0 dB of loss. Maybe with a good pre-amp at the antenna my signal strength might improve. What do you think.

Here's a guideline for loss:

Coax Cable Signal (Attenuation) Loss per 100ft
Loss at RG-59 RG-6 RG-11
1MHz 0.4dB 0.2dB 0.2dB
10MHz 1.4dB 0.6dB 0.4dB
50MHz 3.3dB 1.4dB 1.0dB
100MHz 4.9dB 2.0dB 1.6dB
200MHz 7.3dB 2.8dB 2.3dB
400MHz 11.2dB 4.3dB 3.5dB
700MHz 16.9dB 5.6dB 4.7dB
900MHz 20.1dB 6.0dB 5.4dB
1000MHZ 21.5dB 6.1dB 5.6dB

A pre-amp may help... but remember, a pre-amp boosts 'noise' as well as 'good' signal.

IMO... before you go to the expense of the pre-amp for an indoor antenna, get it as high as possible. Or... get an outdoor antenna mounted in the attic or outdoors if possible.

[hd4me2]

My CM 4228 is strapped to my chimney and is about 25 ft off the ground. The analog UHF signals don't appear ghosty, little or no multipath, but the picture sharpness/clarity is very poor. The CM 7775 that was recommended is a UHF only pre-amp. Maybe when I used the 13 dB amp, after the 50 ft section of cable, with a 3.5 dB NF plus have about 2.5 dB of cable loss from antenna to receiver it was too much in a rather weak signal area.

When the signal meter shows me a strength of 30 % what is it 30 % of ?

Think a good pre-amp is worth a shot?

Thanks for any comments or suggestions.

[Ratman]

Okay... let's start from the beginning.

You have the 4228 mounted on you chimney. Are you certain that it is aimed properly?

Which direction? Towards Balt or DC? Without a rotor, you probably won't get both (I assume you're between the two).

Pre-amps installed close to the STB will not work properly. All you do is amplify noise.

The Signal Strength meters are generally "signal to noise" ratio, not a 'true' strength. So... with 30% that indicative of 30% signal 70% noise.

25' is not very high for reception from 40 miles. What size is the mast? You may consider a 10' mast.

The 7775 will block VHF signals. If you need the VHF station and find you need the pre-amp then the 7775 will not help that at all.

Is the pre-amp worth the shot? Maybe... sorry, but there is never a definitive answer when it comes to reception. :)

[hd4me2]

I aimed the antenna towards the Balt stations using a compass and following the antennaweb.org directional map, 122 deg. I believe that I'm pointed fairly well since my higer signal levels are coming from the Balt. stations not the DC stations: Balt stations are in the 60 to 70% range and DC stations are in the 30 to 35% range, one as low as 20%.

The 4228 is a UHF only antenna, I'm not trying to get VHF just the OTA DTV stations. I'm trying to increase signal levels since once I got hit with a fairly heavy rain I lost even the strongest signal.

I think your right about trying to get up higher. Ricght now I only have a 5 ft mast so I will add another 5 ft and see if it helps. I will also fine tune the azimuth pointing and then see if tilting upwards helps at all.

Any other things you can suggest? I appreciate your thoughts and helpful suggestions.

[kevinw]

I would consider a high gain amp.
http://support.radioshack.com/productinfo/DocumentResults.asp?sku_id=15-1109&Name=Manuals%20for%2015-1109&Reuse=N

From my experiences...

[Ratman]

Compass is good!

But! the compass points at "magnetic" North. You may need to compensate for "geographic" north which is what Antennaweb uses as the direction indicator! (There is a 'formula' to adjust... right now I'm not in a 'search mode') Maybe that's one thing to look into.

Weather... that's the way it is. Bad weather will affect reception. I'm fortunate that I'm only 20miles with an attic mount and get good reception, but with heavy wind, strong rain or snow, my levels do drop.

But if you get good stable signals the majority of the time, maybe you're just 'relieving yourself in the wind' by going through this exercise.

Don't get me wrong... try to achieve 100% is great. I've always got something going on to experiment. But, just don't expect that it's going to be perfect all the time. Even with cable and satellite, there are outages due to weather for one reason or another.

Having fun yet? :)

[hd4me2]

I beg to differ. Read the paragraph I just cut and pasted from antennaweb.

The map shows the distribution of stations around your address. When installing an antenna, you should point your antenna or align your antenna's rotor system to point in the direction of the stations of interest.* The compass arrow in the lower left can help match the orientations on the "Stations" page to the map: the compass arrow shows the direction of magnetic North. Orientations start at 0° (North) and increase clockwise to 360° (North again). So, North-East is 45°, South-East is 135°, etc.

I also double checked this since in my area the angle of declination, difference between magnetic North and true North, is about 13 deg.

[Ratman]

I beg to differ. Read the paragraph I just cut and pasted from antennaweb..

Okay... no need to get snippy. Read what I said, "You may need to compensate for "geographic" north .."

Note the word may.

I read a lot of posts and may overlook some phrases. I try to help as best I can. :bow:

Good luck.

[hd4me2]

Sorry, didn't mean to sound snippy. I appreciate your help and asking good questions to make sure I haven't overlooked anything.

I'll try raising the antenna like you suggested and do some tweaking of the pointing this weekend and let you know if it helped.

Please accept my apologies and thanks again for your insight. :redface:

[kevinw]

Sorry, didn't mean to sound snippy. I appreciate your help and asking good questions to make sure I haven't overlooked anything.

I'll try raising the antenna like you suggested and do some tweaking of the pointing this weekend and let you know if it helped.

Please accept my apologies and thanks again for your insight. :redface:

Try the amp.
I have gone through much of what you are describing. At 40 miles from the towers also, Going through the addition of a mast and guy wires is a pain.

[kevinw]

Okay... no need to get snippy. Read what I said, "You may need to compensate for "geographic" north .."

Note the word may.

I read a lot of posts and may overlook some phrases. I try to help as best I can. :bow:

Good luck.
A little testy today :whistle:

[Ratman]

A little testy today :whistle:

No different than any other day!