DTV reception help requested, please,

cheap

DTVUSA Rookie
#1
TV Fool

Reception: UHF Channel 50,35,32,26-----good
VHF Channel 11,13------------Tolerable with some pixelation (pixels)
VHF Channel 8 --------------intolerable with pixelation and blank spaces
infrequently all channels are of good reception. Trying to get good reception on the above named channels.

Equipement: Channel Master: -#7777 amplifier
Radio Shack #15-1109 amplifier
Radio Shack #VU-190 antennae
Winegard #YA1713 antennae
Access #DTA 1080 Converter Box
All RG6 cable with compression connections.

Arrangement: RX Ant ------CM amp -----splitter--------box
Win Ant-------RS amp-----(connected to splitter above)
Win ant mounted on 10 foot pole on roof of two story house. RS ant is 44 inches below on the same pole. Win ant aimed 195 degrees azimuth and RS antennae 202 azimuth. A few oak tree branches are between antennae and horizon.


Your help is much appreciated.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#2
:welcome: cheap,

Your TVFOOL report contains the following warning:

WARNING: Address was only resolved to street level and might not be that close to your actual location. For more accurate results, try entering a specific address or coordinates.

Since the result is at ground level and isn't based on your your antennas actual height above ground (around 30 feet?) the TVFOOL report is likely to be inaccurate. Please redo the report using your address or GPS with the antenna's actual height and post the new link here. Your personal location will be automatically concealed from public view.

It is possible that using a ten-bar High-band VHF Yagi and a 57 element combination VHF/UHF antenna with amplifers is causing your reception problems, do to WAY to much signal going to your TV set. Amplifiers also amplify noise, so it could be a signal-to-noise ratio problem or a multipath problem.

But, you wrote that you are using a 'splitter' to combine them on one coax and that's absolutely not recommended unless the two antennas are identical, properly spaced and pointing in exactly the same direction.

Here's why: in basic terms, when two antennas are pointing two different directions, the signals from Antenna-A goes to the splitter and half of it goes to your TV set BUT the other half goes to Antenna-B and it is re-radiated. 50% signal loss or more.

The signal from Antenna-B goes to the splitter and half of it goes to your TV and the other half goes to Antenna-A and is also re-radiated. Again, a major loss of signal.

Next, both antennas may 'see' some signal from a given station, but one signal may be an 'echo' from a mountain, a building, etc. and your TV Tuner or in this case Converter Box cannot decipher the same signal arriving at two different times: this is what 'Ghosts' were caused by in Analog, but DTV is go or no-go. That is a multipath problem ... "multiple signal paths".

There is one other exception to the above antenna rule and that's when combining a VHF antenna and a UHF antenna regardless of where they are pointing and that can be done with a device similar to a 'splitter' called a UVSJ combiner. Your 44" antenna seperation is good for the UHF band: I ran the numbers a while back and its about 36" at (real) channel 35.

I hope this helped! Were looking forward to an updated TVFOOL report.

Jim
 
Last edited:

n2rj

Moderator
Staff member
#3
I assume the channel #'s you gave us are real (physical) channels and not virtual ones.

I would do it this way:

1. Disconnect everything

2. Open up your CM7777 and change it from "combined" to "separate." There is a switch on the inside to do that. While you are at it, enable the FM trap. FM harmonics can interfere with high VHF. In any case you won't lose anything (except FM of course).

3. 8, 11 and 13 appear to be in the same direction. Use the winegard YA1713 for those. Put it higher than the RadioShack antenna, get it as high as you can, aim it and peak the signal for those channels with your TV an d converter box (you'll need a helper of course). When done, connect the YA1713 to the VHF side of the CM7777.

4. Connect the RadioShack antenna to the UHF side of the CM7777. It doesn't appear that you're using it for VHF anyway.

5. Connect the downlead to the channel master power supply and then directly to your converter box. No splitter needed.



You don't need:

Radioshack amp (it's actually an antennacraft 10G212)
Splitter

If you're not in love with the oak tree it might help to trim the branches out of the way but unless they are leafy they probably aren't doing much of anything.

If that still doesn't clear up things for you, you may be able to combine two YA1713's and get an additional 2.5dB. But we won't go there just yet.

So in the end you'll end up with:

Winegard YA1713 -------------VHF side of CM7777
......................................................................| ----internally combined-------CM power supply---DTV converter box ---------> TV set
RadioShack antenna ----------UHF side of CM7777
 
Last edited:

cheap

DTVUSA Rookie
#4
Jim,

I am an old man, 79, and not computer literate so I have to get someone to help me on the computer comply with your request to redo TVFOOL map. I tried three times and keep getting the same results. I have put in the street address with the zip code and I don't know what else to do.

As regards to the arrangement you suggested, I have tried both antennas seperately without splitters and with various settings on the amplifer. Similar to the computer, I have trouble moving the ladder and climbing up the two story house and changing the arrangement. I then have more trouble measuring the results. Sometimes the signal strength is 100% and everything is wonderful on all channels, but then the next day channel 8 is intolerable with blanks and pixels but within minutes the signal returns at maybe 40%. The arrangement in my question has provided the best results in almost a year in trying to improve reception and answering the question, "why don't I get cable?"
 

cheap

DTVUSA Rookie
#5
n2rj,

Please see my reply to Jim. Yes all channel numbers are real. I have tried the Winegard and the CM amplifier with an old 4-bay UHF antenna arranged as you suggested. Again, the results were good but they did not eliminate pixels and blanks on channel 8. In regards to the oak tree I installed a pole infront of the tree on the ground with the above arrangement and similar results. I have tried TVFOOL with different antenna height and found higher signal predicted at lower levels (10ft.). So thanks but please make any suggestions easy.
 

n2rj

Moderator
Staff member
#6
Hi cheap,

Do you know how to use Google Earth? That would make things very easy to find your GPS coordinates (latitude and longitude).

As for it being easy, unfortunately the stations you want to receive are some 80 miles away so I'm afraid you will need height first and foremost.
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#7
cheap,

Take a look at the two links below to an excellent website that help explain RF Propegation. The first link makes an arguement where lowering your antenna a couple feet may help establish a stronger signal: its explained in the 4th diagram above the Beetle Bailey cartoon. I have personally experienced this on two different antenna setups (one was sensitive within a 6" antenna height change) and about a month back I suggested this to another newbie on the Forum and he had excellent results, by lowering his antenna two feet. Click here: --> Siting the antenna

The same website has some information on Multh-path interference and noise. You will have to scroll down (alphabetically) to get to these topics. Click here: --> Glossary G to Q

I have to I agree with n2rj as far as removing the Radio Shack amplifier and using your CM-7777 to properly combine your antennas ... that way your two antennas won't be working against each other.

Its hard to predict if FM Stations are contributing to your problems but again, n2rj is right about turning on the FM-trap built into the CM-7777, after all, you're trying to receive Channel 8 and the FM Broadcast band is very close in frequency, just below Channel 7.

If you're not up to tackling this, perhaps a neighbor or two would be willing to help you. Bribe them with a BBQ and beer (afterwords)!

Regarding your few Oak Tree branches, I have can't say if they are players here, but I'll load two photos here in my next post showing what my antennas are 'seeing thru' without any problem. I am sceptical about their significance, again based on personal experience with my own setups and others I have installed. Stand by for a follow-up post with 'tree-photos'.

Jim

PS If you send me your address, zip code and actual antenna height OFF-LIST here as a personal messsage, I'll run your TVFOOL report and post the result: again, the Forum will conceal your personal data.
 
Last edited:

n2rj

Moderator
Staff member
#8
Regarding your few Oak Tree branches, I have can't say if they are players here, but I'll load two photos here in my next post showing what my antennas are 'seeing thru' without any problem. I am sceptical about their significance, again based on personal experience with my own setups and others I have installed. Stand by for a follow-up post with 'tree-photos'.
Well I have a hickory tree blocking my antennas and it is indeed affecting the signal. I've seen the wind blow then suddenly the signal meter drops. It's not signal strength, it's multipath for sure. The leaves, not the branches. But of course like everything YMMV.

Its hard to predict if FM Stations are contributing to your problems but again, n2rj is right about turning on the FM-trap built into the CM-7777, after all, you're trying to receive Channel 8 and the FM Broadcast band is very close in frequency, just below Channel 7.
The FM band is 88-108 and channel 8 is a bit far. Why I said enable the FM trap is for two reasons -

1. If any strong FM stations are nearby they may be overloading the amp. CM7777 is prone to overload from strong signals.

2. Harmonics. Channel 8 is 180-186MHz, which falls in the 2nd harmonic of 90-93MHz FM. Any strong stations on 90-93MHz on the FM band could potentially cause a problem.
 
Last edited:

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#9
cheap,

I wrote above that I don't subscribe to trees always being a problem and a few Oak branches in your antennas' view may or may not be an issue. I have my doubts.

This photo below is pointing North from my home and the 80 foot tall Evergreen Tree's closest branch is within 10 feet of my Project-35 antenna. Twenty more feet to the North is another similar tree, 70 feet tall. Across my walkway is a 2.5 story home, and then the hill rises with tri-plex apartment houses and homes and the hill gains at least 75 feet, plus the height of the homes. My antenna is currently 18 feet over my roof and I receive KVOS-12 (35) Bellingham (580 kW ERP) with an average 'signal strength' of 65. Their transmitter is 76 miles away. No amplifiers are used and it has an RG-6 cable run of about 75 feet.



In the interest of being 'neighbor-friendly' last summer I installed a test-mast in my backyard facing West and I captured a 40 watt translator at a range of 17 miles to receive my CBS affiliate using a CM-4221. No amplifiers were used in spite of about 100 feet of RG-6 loss. Here's a photo of EV's Kosmic Super-Quad being tested in the same location earlier this Spring, before the trees completely filled out. (Seriously)



So, that's why I am a skeptic when it comes to trees.

However you manage it, let's get back to removing the RS amplifier and combine your antennas with your CM-7777 and verify the FM-trap is on as n2rj suggested.

Best regards, Jim

PS I have no clue what it takes to size photos here: working on it. At least the postage stamp sized ones are history. UGH!
 
Last edited:

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#11
n2rj,

The only 'problems' I have experienced is signal ducting from KVOS-12 (35) that it actually came in on my west-pointing antenna (!!!) two evenings, and two complete drop-outs on my Project-35 over the entire winter. The West-pointing antenna has never lost the CBS translator (recently bumped from 40 to 900 watts ERP) nor my Fox-13 or KBTW-20 (14) and both of those are LOS.

Jim

PS Hey, take a look at my tested antennas album and look for the Winegard HD-9095: that's representative of what I have to deal with looking East! Per my statement to the left under my Avatar, "fighting 1 and 2 edge..." ... I don't like to lose. I shipped that antenna to Piggie for testing and am awaiting his results, when his weather clears.
 
Last edited:

n2rj

Moderator
Staff member
#12
Wow, I just had a look... unreal. I'm due back up the tower soon to install RG11 in place of the RG6 downlead I have now.

The 9095P is one I am considering to receive philadelphia stations, maybe a 2 stack of those. Reason being that it easily side mounts on the tower. Otherwise I'm going to have to buy a side arm (~$300) or fabricate a cantilever mount.
 
#13
TV Fool

Reception: UHF Channel 50,35,32,26-----good
VHF Channel 11,13------------Tolerable with some pixelation (pixels)
VHF Channel 8 --------------intolerable with pixelation and blank spaces
infrequently all channels are of good reception. Trying to get good reception on the above named channels.
Cheap,

The VHF reception results you are seeing are pretty typical of what I usually see from a TV FOOL report with numbers like those. (If that report is similar to your actual location) Unfortunately, I feel you are doing about the best you can, especially if you have tested VHF with no amp directly to 1 TV. Channel 8 is only transmitting a measly 14kws in your direction which isn't helping either.

I am thinking the majority of your VHF issues may have more to do with electrical interference(s) since you are having better luck with the UHF's from the same area. VHF reliability is tough with noise margins that low.
 
#14
The FM band is 88-108 and channel 8 is a bit far. Why I said enable the FM trap is for two reasons -

1. If any strong FM stations are nearby they may be overloading the amp. CM7777 is prone to overload from strong signals.

2. Harmonics. Channel 8 is 180-186MHz, which falls in the 2nd harmonic of 90-93MHz FM. Any strong stations on 90-93MHz on the FM band could potentially cause a problem.
The FM trap in the 7777 preamp is not very effective in the bottom part of the FM band. Note that KETX on 92.3 is roughly 70 db stronger than TV channel 8.

Consider using a HLSJ in front of the VHF input of the 7777 to eliminate all the FM signals.

A Winegard AP 2870 would have been a better choice than the 7777. It has less gain and a tunable FM trap.
 
Top