Help Solve a Single Channel Problem

[linuxman]

Since the digital transition, I recently noticed a single channel dropping A/V on my Diamond ATSC receiver. The Toshiba TV combo analog/digital tuner has played it fine.

I was using an old VHF/UHF/FM antenna I bought off Craig's list a couple of years ago with a pre-amp. See pictures below.

I went out Monday and bought a Digi-Tenna DUV-XF antenna to replace the old one. See the link for specs and the pictures below.

I have been struggling all week trying to get all the channels viewable from my home to work on my setup. I now have the antenna about 25 feet off the ground. It is on a tri-pod and about 12 foot off my flat commercial roof.

Here is the "diagram" of how I have it wired.

90 ft. of new solid copper RG-6 swept tested to 3 Ghz from antenna to living room.

In the living room, I have and can use either a barrel connector or a new Winegard HDA-200 single output distribution amplifier to go 20 ft. from the living room to my den and hook into a new 4 way splitter.

The splitter goes to my Toshiba TV tuner, my Diamond ATSC tuner, to the living room tv, and to my HDHomerun tuner.

I was using a pre-amp at the antenna while using the old antenna, and have tried using the pre-amp with the new antenna and still have the same problem which is why I bought the distribution amplifier.

I tuned the antenna directionally for best signal with my HDHomerun tuner and laptop on the roof yesterday.

Here is the problem:

Without using an amplifier, coming straight from the antenna to the living room and using the barrel connector to get to my den, I can get all channels excepting that one channel is extremely weak. I am fearful that the first rain storm and it will drop out.

Using the pre-amp, or the distribution amp, I can raise the signal strength, but with the amplifier added, the weak channel 47 is hit and miss. It will display fine for a while and all of a sudden drop out.

I have gathered some data and thought some of you might be able to analyze it and tell me what to try next.

Take a look at the chart, and the pictures and let me know any suggestions you might have. I have not yet tried using the pre-amp and the distribution amp in combination, so that may be an option. The distribution amp does have a potentiometer, but I have not messed with that either. I don't know what I am doing with the POT, so have not messed with it. The distribution amp also has an FM trap, and I have tried switching it both ways and it seems to have no effect.

Here is the chart of data:

....

					My OTA Signals

Channel		W/O Amp					W/Amp
	TV		Diamond		             TV			Diamond
	 Sign 	SNR(DB)	SQ	                         Sign 	SNR(DB)	SQ
14 Green 62	23		91			87	28		99
24 Rel	62	23		99			87	28		99
26 CW	89	28		99			90	28		99
31 ABC	97	30		99			97	30		99
35 NBC	90	28		99			92	28		99
39 PBS	87	28		99			97	31		99
43 CBS	97	31		99			97	31		99
47 MyTV	37	17		67			74	25		67-71 if it falls below 67, A/V drops out

Analog
7 HSN	BW Snow						Color Snow
16 DS	BW Barely Picture				Snowy
22 TBN	Almost Clear					Clear
33 TBN	BW Barely Picture				No Picture
51 DS	Color Snowy					Almost Clear
......

Here are the pics:









Any help would be appreciated.

 

[tvropro]

With UHF signals at some distance there are hot spots and dead spots. First off I would use a Winegard low noise preamp since this will overcome any coax loss. You may also want to walk the roof with your antenna to find where the best spot will be to mount it. Since it's flat that shouldn't be an issue. Your current preamp may be adding noise that digital don't like and causing cliff effect. Another thing you can try is connect a DTV converter box up on the roof and see how the signal is with a short coax. If its good get a good preamp and call it a night. I have used Winegard preamps for Dxing channels 90+ miles away for years and always had good results.

Look here for my OTA antenna tricks I have done:

TvroPro Electronic Lab

 

[No Static At All]

Have you tried moving the antenna up or down on mast? The antenna may be sitting in a dead spot for UHF 47. A couple inches either way can possibly make a huge difference. I see this happen a lot with UHF.

Higher is not "always" better.

 

[linuxman]

With UHF signals at some distance there are hot spots and dead spots. First off I would use a Winegard low noise preamp since this will overcome any coax loss. You may also want to walk the roof with your antenna to find where the best spot will be to mount it. Since it's flat that shouldn't be an issue. Your current preamp may be adding noise that digital don't like and causing cliff effect. Another thing you can try is connect a DTV converter box up on the roof and see how the signal is with a short coax. If its good get a good preamp and call it a night. I have used Winegard preamps for Dxing channels 90+ miles away for years and always had good results.

Look here for my OTA antenna tricks I have done:

TvroPro Electronic Lab

Thanks for the suggestions.

I'll try and give them a shot tomorrow.

Have you tried moving the antenna up or down on mast? The antenna may be sitting in a dead spot for UHF 47. A couple inches either way can possibly make a huge difference. I see this happen a lot with UHF.

Higher is not "always" better.

I'll run it up and down tomorrow too.

Never quite thought about lower might be better.

Thanks!!

 

[trinity13]

Have you looked into the "Gray-Hoverman" antenna?
You can build it cheap and it works great.

 

[Inno]

Also see if it's level...........not sure if it's a huge factor with that type of antenna but with my old Channel Master parabolic it sure is.

I also agree with the "higher not necessarily being better" idea too...........location location location...........with antennas a lot of times it's trial and error.

 

[meinename]

Love the Digi antenna!
Don't let your fears get the better of you.

Looking at your TV Fool, 46.1/47 should be an easy job. I agree that you need to move the antenna about a bit first.

First In My Experience, channels 45 and higher are fussy about antenna position.

Second that bridge has me shaking my head... a major source of strong multipath, trains, cars or otherwise with that chuck of metal being so close. You need distance and some obstacles between your antenna and the bridge.

In one case I had a metal roof between the antenna and the highway at 45 miles.
The highway and the antennas pointed parallel to each other. The cars and trucks would cause a major ghost when they traveled between 30 and 45 degrees to the antenna. Mind you in this case I was checking 2 houses, neighbors to each other, at 50 and 60 yards from the highway.
The farther house with the roof had no problem with reception. Weak but stable.
The nearer house closer to the highway needed several thing changed to fight the incessant abnormal multipath.
Had to switch out the RCA DT800B1 with a Zenith DTT-900
Zenith had common-mode loss fixed with a ferrite sleeve
Needed to attenuate the Ghosts, found a splitter that did the job.
Used no Amplifiers or pre-amps at either house.

This is one of those cases where I believe you have a strong ghost in the signal. The amp and pre-amp may seem to help or make it worse, but your TVFool received power levels say that those aren't needed at all.
I've found consumer Distribution amps aren't linear enough for short run amplification of digital signals.
Your signal strength may be going up but now the echoes and other Quality killers are stronger as well.

If you have any kind of attenuator, try that on the connection to the Diamond
I've resorted to old 4dB splitters to get multipath out.

I've also been pleasantly surpirised at taking measures to lessen "common mode" loss.
Throw a ferrite sleeve round the coax within 2 inches of the F-connector.
Place another ferrite sleeve around the power-cord at 3 inches from the box.
The ferrite sleeve on the coax may or may no do anything.
My Olevia at 8 miles with tons of strong local multipath gets above threshold Quality with one placed on the coax 1.5 inches from the F-connector.

All that writing and I JUST NOTICED THE BUD WITHIN 10 FOOT of the antenna! :rant:
I have such problems with the Digital TV reception and the Horizontally polarized signals. A full BUD on plane with the antenna that is NOT in the Null zone of the antenna (around 90 and 270 degrees usually) will cause strong echoes.

Move the antenna back... or lower it below the BUD reflector.

GOOD LUCK!

 

[Inno]

All that writing and I JUST NOTICED THE BUD WITHIN 10 FOOT of the antenna! :rant:
I have such problems with the Digital TV reception and the Horizontally polarized signals. A full BUD on plane with the antenna that is NOT in the Null zone of the antenna (around 90 and 270 degrees usually) will cause strong echoes.

Move the antenna back... or lower it below the BUD reflector.

GOOD LUCK!

Which why most times higher is better........unless your 10' BUD is higher than your antenna.

 

[TRG]

I tuned the antenna directionally for best signal with my HDHomerun tuner and laptop on the roof yesterday.

Which channel did you use to tune the antenna? At 160 degrees az. channel 47 is a little further south than the rest. Try tuning to that one.

 

[linuxman]

Love the Digi antenna!
Don't let your fears get the better of you.

Looking at your TV Fool, 46.1/47 should be an easy job. I agree that you need to move the antenna about a bit first.

First In My Experience, channels 45 and higher are fussy about antenna position.....

If you have any kind of attenuator, try that on the connection to the Diamond
I've resorted to old 4dB splitters to get multipath out.

First thing this morning, I went to town and traded the distribution amp for a Winegard AP-8275 Pre-Amp.

Got back and took the tools to the roof for a re-tune of the antenna. I used a Zenith DTV tuner with my mini-dvd for screen output to tune the dish.

I moved it on the roof some and backed it away from the BUD about 10 feet. As big as my roof is, you'd think I would have more room to play, but i have 8 BUDs up there along with an assortment of Primestar dishes, plus the South side has big trees, and the East side has big trees. So my "window" view the the SE towards the city is limited.

I actually got my best signal on channel 47 through the big tree to the South. In the first picture below, you can see the line I drew. But having the antenna in that direction did cause some degradation to the other channels further East, so I moved the antenna slightly further to the East and compromised.

Tried moving the antenna up and down as much as 2 feet lower, but no better signal.

I finally settled for what I had which was actually a little lower than I had yesterday.

Put on the new Pre-Amp, and buttoned everything up.

Got inside and all was pretty much the same except that I had less signal on channel 47 than yesterday. I was a bit discouraged, and came to the computer to ask about perhaps mounting 2 antennas. Using the new one pointed far south, and the old one pointing more to the East, and I still might do that.

Instead, I re-read the suggestions above, and ran across meinename's suggestion which I quoted above.

I found an old "Archer" 4 way splitter from days gone by, and stuck it on the connection to the Diamond.

BAM! The quality on channel 47 on the Diamond jumped from 63 to 75, and I have a pretty stable A/V.

So all the work, all the re-running of cable, the new Pre-Amp, and the problem might have been solved with an attenuator.

If you could tell me what to buy, I'll pick 2 up in the morning, because I have another Diamond 9000 in the living room doing the same thing.

Also, what are your thoughts on combining the two antennas so I can point the new antenna farther South?

Thanks for all your help!

See the pics below:

 

[ljdonato]

I found an old "Archer" 4 way splitter from days gone by, and stuck it on the connection to the Diamond.

Hi

I been following with great interest, since I have a pretty similar problem.

Question: Where did you attached the splitter, near the antenna or near the receiver?

Happy you have solve your problem...

Thanks

 

[linuxman]

Hi

I been following with great interest, since I have a pretty similar problem.

Question: Where did you attached the splitter, near the antenna or near the receiver?

Happy you have solve your problem...

Thanks

I attached the splitter that is acting as an attenuator next to the receiver with a 6 inch piece of coax.

The problem isn't solved entirely yet, but I think I am on the right track. Got to get that SQ just a little more stable.

Just need a few more answers from the guys that know more than I do.

 

[ljdonato]

Thanks!! I'll try that.

Will any splitter do? (I have an old 3-way)

 

[tvropro]

They sell attenuators in different db ranges. A 4 set coupler is -7db down so I would try a -6 and see what happens. I wouldn't combine the two antenna's on the same lead it can cause you more headaches than it's worth. There are ways but it's not a 123 solution. Use two down leads and an A/B switch if you want to use both.

 

[linuxman]

They sell attenuators in different db ranges. A 4 set coupler is -7.5db down so I would try a -6 and see what happens.

Thanks Guy!

I'll try that.

What is your opinion on combing the two antennas?

Any thoughts?

 

[TRG]

Thanks Guy!

I'll try that.

What is your opinion on combing the two antennas?

Any thoughts?

Antennas Direct | UHF / VHF Antenna Combiner from Antennas Direct

 

[nazareno7]

When combining two or more antennas try to connect them using a twin-lead cable. Join them using a single 300 -> 75 transformer. That way you can keep signal loss to a minimum.

 

[tvropro]

Thanks Guy!

I'll try that.

What is your opinion on combing the two antennas?

Any thoughts?

Fred, UHF & VHF can be combined easily. If you want to use two UHF or VHF antenna's thats where it gets hairy. The problem with combining two antenna's on the same band unless you use single channel yagi's and sophisticated matching networks or combiners, they do more harm than good. You can get multipath, swr mismatches etc. It can be done but isn't as simple as using a splitter backwards.

 

[meinename]

2 things I didn't get to in my last post
They both focus around the Zenith DTV box

1. IME the Zenith signal meter is purely a Quality meter. If the subchannel is dropping out but other channels are not, the meter will bounce on the Zenith.
What happened was the local that was carrying This TV had a poor aim of their dish for the THIS TV feed on top of the time that the feed would drop out, tile and such. The Zenith meter would bounce with the signal, but the ABC-HD feed on the same RF channel would register solid on the Zenith meter

2. It is believed the Zenith and all other CECB DTV boxes with an LG-based tuner have the 6th generation tuner. The important improvement is that this was the best handler of multipath by a large margin compared to any previous ATSC tuner.
An echo/ghost only needs to be 3dB weaker than the main signal to be ignored with the 6th gen LG tuner.

So when debugging with a LG tuner Zenith or Sanyo based from this list:
[ame="http://en.wikipedia.org/wiki/Comparison_of_CECB_units"]Comparison of CECB units - Wikipedia, the free encyclopedia[/ame]
Try attenuating and if the dropouts stop it is a multipath problem.

Older tuners will need more attenuation of Main signal vs. multipath ghost
I've see adjustable 20dB attenuators
Winegard TA8700 Variable Attenuator 0-18 dB for Off-Air Antenna (TA-8700) | TA-8700 [Winegard]
20dB Variable Attenuator for VHF UHF HD Off-Air Reception 1296F | 1296F [Antennas Direct]

Combining antennas for more signal is a trick. Doing so without a Signal Combiner will only add to your multipath woes. Try it with some CECB's on a spare set of antennas, not the main one.

 

[linuxman]

The problem with channel 47 has been solved.

I went to town this morning and picked up a .3, .6, and .10 db attenuator for my Diamond 9000HD ATSC tuners.

None of them fixed the problem any better than the 4 way splitter above. I was just about to go up to the roof and start re-adjusting the antenna because I know I had better signal with channel 47 on it 2 days ago.

The phone rang, and I had to make a run into a client to fix a computer problem. I was thinking to myself on the way down and asked myself a question.

Why am I working so hard trying to "dampen" the signal down for the Diamond? My answer to myself was that maybe I was amplifying the signal too high to begin with. The Digi-Tenna Xtreme Deep Fringe antenna is a marvelous antenna to begin with. Maybe the AP-8275 and the Distribution Amp I had before were both putting out too much signal.

I went back by Skywalker and picked up a Winegard AP-8700 and put it on the antenna when I got home.

The Signal Quality on the Diamond jumped to 99% on the Diamond on channel 47.

The Diamond ATSC tuner is much more sensitive than the tuner in my TV, and I picked up 4 new channels that I didn't know were there.

I picked up the 4 WSIU PBS channels listed on the TVFool image above, and according to the image, that tower is 99 miles away.

Needless to say, that opened up a whole other can of worms for me.

So Linuxman is a very happy camper today.

I will go back to the roof on Saturday when it is going to be cool and nice again so I can put a final tune and position on the antenna with this amplifier installed.

I think the lesson I have learned is to match the antenna with the amplifier needed, and not to over amplify.

Thanks for everyone's help!!!

It is much appreciated. :